Search

Background: In multiple sclerosis (MS) the quantitative role of relapses in Expanded Disability Status Scale (EDSS) worsening beyond the recovery phase is not well known. Most studies have examined the predictive role of early relapses in more distant endpoints. Relapses and worsening may be associated because they could be independent effects of the same underlying disease characteristics without causal relationship. With the design of the present study we aim to estimate the direct effect on disability of relapses., Methods: We used data from the obligatory bi-annually registration in the Danish Multiple Sclerosis Registry of relapses and EDSS for all patients treated with disease modifying drugs for relapsing/remitting MS from 1996 to 2015 with exclusion of patients in whom no relapses had ever been recorded during treatment. We paired two consecutive control periods into study intervals which were the actual study units. Study intervals were qualified and included if they were at length 12-24 months, with EDSS ≤ 5.5 at start, and if a preceding relapse had been no closer than nine months to the EDSS assessment at the start or end of the study interval to eliminate relapse-related temporary EDSS worsening. We compared EDSS worsening in study intervals with and without relapses. The same patients could contribute with study intervals with and without relapses. For statistical analyses we used Generalized Estimating Equations to account for intra-patient correlations., Results: We analysed 5187 study intervals from 2015 MS patients. The mean of EDSS increase was 0.205 units in qualifying study intervals with relapses and 0.065 without relapses when adjusted for length of study interval, sex, and EDSS at start of interval; p < 0.0001. However, the effect of relapses on EDSS was absent in male patients (p = 0.521), and when EDSS was ≥ 4.0 at start of the study interval (p = 0.726)., Conclusion: Relapses play an independent and significant role for worsening of MS in patients under disease-modifying therapy (DMT) and eliminating relapses would not only free the patients from the temporary perils of relapses but would also reduce the worsening of the disease., (Copyright © 2019. Published by Elsevier B.V.)

Multiple sclerosis is a disease with a highly variable incidence worldwide. While knowledge about multiple sclerosis risk factors has grown over the years, the aetiology of multiple sclerosis has still not been fully established. We examined multiple sclerosis incidence rates among first-generation immigrants in Denmark, a high-incidence country, and their Danish-born children (second-generation immigrants), to evaluate the importance and timing of exposure to environmental factors in the aetiology of multiple sclerosis. By means of the Danish Civil Registration System we identified 9 121 187 individuals living in Denmark between 1968 and 2015, including 1 176 419 first-generation and 184 282 second-generation immigrants. Study participants were followed for multiple sclerosis in the Danish Multiple Sclerosis Registry from 1968 to 2015. The relative risk (RR) of multiple sclerosis according to immigration status was estimated by means of multiple sclerosis incidence rate ratios obtained in log-linear Poisson regression analysis. Altogether, 16 905 cases of multiple sclerosis were identified in the study cohort, 578 among first-generation and 106 among second-generation immigrants. Multiple sclerosis risk among first-generation immigrants whose parents were born in low, intermediate and high multiple sclerosis risk areas were 21% (RR = 0.21; 95% CI: 0.16-0.28), 43% (RR = 0.43; 95% CI: 0.36-0.50) and 75% (RR = 0.75; 95% CI: 0.67-0.83), respectively, of that among ethnic Danes (test for trend P < 0.0001). First-generation immigrants arriving in Denmark before age 15 years had a multiple sclerosis risk higher than that in their country of birth but lower than that in Denmark, reaching on average 69% of the multiple sclerosis risk among ethnic Danes (RR = 0.69; 95% CI: 0.55-0.87). Multiple sclerosis risk among individuals who came to Denmark at a later age remained closer to that of their country of birth, corresponding to 45% of the multiple sclerosis risk among ethnic Danes (RR = 0.45; 95% CI: 0.41-0.49). Our study supports the idea that environmental factors exerting their role in childhood or adolescence may be of aetiological relevance in multiple sclerosis., (© The Author(s) (2019). Published by Oxford University Press on behalf of the Guarantors of Brain. All rights reserved. For Permissions, please email: journals.permissions@oup.com.)

Background: Infections are suspected environmental triggers for multiple sclerosis (MS). The relationship between the timing and cumulative number of childhood infections regarding pediatric MS risk is uninvestigated., Objectives: To investigate whether childhood infections contribute to pediatric MS., Methods: A nationwide nested case-control study with detailed MS case ascertainment including chart review was undertaken. For each MS case, we selected five control children using density sampling from the entire Danish population, matching controls to children with MS by sex and birthdate. We analyzed data with the cumulative number of childhood infections as exposure and MS as outcome. Hazard ratios (HRs) including 95% confidence intervals (CIs) were estimated using Cox regression., Results: We identified 212 children with MS and 1,060 controls. Median age at MS onset was 15.3 years (range: 7.6-17.8 years); 72% were girls. Each infection during the preceding 3 years increased the hazard for MS by 11% (95% CI = 1.01-1.22, p = 0.04); having 5+ infections compared with 0-4 infections in the preceding 3 years doubled the hazard for MS (HR: 2.18; 95% CI = 1.12-4.30, p = 0.02)., Conclusion: Children with MS appeared to have more infections in the 3 years preceding MS clinical onset; accordingly, immune response to infections may influence MS pathogenesis.

Objectives: To estimate the nationwide population-based incidence, prevalence, and geographical distribution of neuromyelitis optica (NMO) spectrum disorder (NMOSD) in Denmark based on the 2015 International Panel for NMO Diagnosis (IPND) criteria., Methods: We conducted a multicentre, historically prospective study. Data were sourced from the Danish National Patient Registry, the Danish Multiple Sclerosis Registry, departments of neurology, and laboratories providing aquaporin-4 antibody test. Cases were selected based on the 2006 Wingerchuk and the 2015 IPND criteria and were individually validated by an expert panel., Results: We confirmed NMO in 30 cases (2006 criteria) and NMOSD in 56 cases (2015 IPND criteria) between 2007 and 2014. Defined by the 2006 criteria, the incidence of NMO was 0.029 per 100,000 person-years (95% confidence interval [CI] 0.014-0.051), and the prevalence (aged 16 years and older) was 0.566 per 100,000 (95% CI 0.370-0.830). Based on the 2015 IPND criteria, the incidence of NMOSD was 0.070 per 100,000 person-years (95% CI 0.046-0.102), and the prevalence (aged 16 years and older) was 1.09 per 100,000 (95% CI 0.808-1.440), without regional differences., Conclusions: Our estimates of incidence and prevalence are similar to other Caucasian population-based studies using the 2015 IPND criteria. We found no geographical clustering in Denmark., (Copyright © 2018 The Author(s). Published by Wolters Kluwer Health, Inc. on behalf of the American Academy of Neurology.)

Aim: The International Paediatric Multiple Sclerosis Study Group (IPMSSG) has proposed criteria for acute disseminated encephalomyelitis (ADEM) not evaluated in clinical practice. Our objective was to assess epidemiological implications of the IPMSSG criteria for ADEM in a cohort study using prospectively collected data., Method: We identified all diagnosed cases of ADEM in Denmark between 2008 and 2015 from the Danish National Patient Register by International Classification of Diseases 10 codes assigned to acute demyelinating episodes, and we reviewed all medical records to validate ADEM., Results: We found 52 children up to the age of 18 years with a verified clinical diagnosis of ADEM (incidence rate 0.54/100 000 person-years; all had abnormal brain magnetic resonance imaging). Only 18 (35%) fulfilled the IPMSSG criteria regarding encephalopathy and polyfocal neurological deficits. Among all 52 children with ADEM, 33 per cent had clinical sequelae after a median follow-up of 4 years 6 months (range: 10mo-8y 3mo). Surprisingly, none progressed to multiphasic ADEM or multiple sclerosis, but median age at end of follow-up was only 10 years 9 months (range: 2y-24y 3mo)., Interpretation: Among 52 children with ADEM, none converted to multiphasic ADEM or multiple sclerosis (median follow-up: 4y 6mo; range: 10mo-8y 3mo). Applying the IPMSSG criteria to all children with a diagnosis of ADEM leaves 65 per cent of the cases without a diagnosis and lowers the incidence rate of paediatric ADEM., What This Paper Adds: The incidence of paediatric acute disseminated encephalomyelitis (ADEM) was 0.54 per 100 000 person-years in children younger than 18 years. Only 35 per cent of children with ADEM fulfilled the International Paediatric Study Group consensus criteria. ADEM in clinical practice was primarily based on magnetic resonance imaging findings. Paediatric neurologists diagnosed ADEM in the absence of encephalopathy. None of the children with ADEM progressed to multiple sclerosis/multiphasic ADEM during follow-up., (© 2018 Mac Keith Press.)

Background: The aetiology of multiple sclerosis (MS) is largely unknown, but commonly assumed to be a complex interaction between genes and environmental exposures, presumably during early life. To evaluate the possible importance and timing of environmental exposures we investigated the spatial variation in the risk of MS in Denmark according to residence at birth, age 15, and clinical onset of disease., Methods: We carried out a nationwide, register-based case-control study including 12 993 Danish MS cases with onset of disease 1971-2013. Information on exact residential addresses was available for all study subjects in the Danish Civil Registration System. The spatial variation in risk of MS was estimated by kernel regression., Results: We identified spatial variation in the risk of MS according to residence at birth, age 15, and onset of disease. Several high- and low-risk areas were identified across the country with some variation between birth, age 15, and onset., Conclusions: Small-scale geographical variation in the risk of MS suggests that local environmental risk factors could be at play and may be related to life style factors., (Copyright © 2018 The Authors. Published by Elsevier B.V. All rights reserved.)

Background: The incidence of acquired demyelinating syndromes (ADS) including multiple sclerosis (MS) has never been investigated in a Danish pediatric population., Objectives: We estimated the nationwide age- and sex-specific incidence of pediatric ADS including MS., Methods: Data were sourced from the Danish Multiple Sclerosis Registry, providing cases of pediatric MS for 1977-2015, and the National Patient Register, providing cases of ADS during 2008-2015. All medical records were reviewed to validate the register-based diagnoses., Results: We identified 364 cases of pediatric MS occurring during 1977-2015 (incidence rate = 0.79 per 100,000 person-years). MS was exceptionally rare before puberty, but the incidence rose considerably from 9 years in girls and 11 years in boys. The female-to-male ratio was 2.5; the median age at onset was 16 years (range = 7-17 years). The MS incidence rate was relatively stable through the study period. During 2008-2015, we identified 219 ADS cases. The incidence was 2.29 per 100,000 person-years with considerable differences in the age peaks for the separate ADS., Conclusion: The incidence rates of MS and other ADS in Denmark were higher than those reported for some other European countries. Referral bias and classification differences may account for this disparity, in particular the age-intervals and the definition of onset.

Objective: To describe the pattern of development of incidence of multiple sclerosis (MS) over 60 years in Denmark with age-period-cohort analyses and seasonality of birth., Methods: Data on virtually all patients with onset of MS have since 1950 been prospectively recorded and kept in the Danish Multiple Sclerosis Registry with multiple sources of notification. Annualized incidence rates per 100,000 were directly standardized to the European Standard Population., Results: We have registered 19,536 cases with clinical onset of confirmed MS in Denmark from 1950 to 2009. From the 1950-1959 to the 2000-2009 onset period, incidence more than doubled in women, with an increase from 5.91 (95% confidence interval [CI]: 5.60-6.24) to 12.33 (95% CI: 11.91-12.75) per 100,000 per year compared with a modest 24% increase in men from 4.52 (95% CI: 4.24-4.81) to 6.08 (95% CI: 5.79-6.38). With age at onset of 50 years and older, incidence increased with a factor 4.30 in women and 2.72 in men. The female/male sex ratio increased over time and with year of birth. Age-period-cohort analysis revealed a significant birth cohort effect in addition to the age and period effect. We found no statistically significant seasonality of births., Conclusion: The incidence of MS has doubled in women, most pronounced with late onset, and has only modestly increased in men. Lifestyle changes in the female population that could include fewer childbirths, increased occurrence of obesity, and increased cigarette consumption may have a role., (© 2018 American Academy of Neurology.)

Objective: To investigate whether smoking in patients with relapsing-remitting multiple sclerosis (RRMS) treated with interferon beta (IFN-β) is associated with the relapse rate and whether there is an interaction between smoking and human leukocyte antigen (HLA)-DRB1*15:01, HLA-A*02:01, and the N-acetyltransferase-1 ( NAT1 ) variant rs7388368A., Methods: DNA from 834 IFN-β-treated patients with RRMS from the Danish Multiple Sclerosis Biobank was extracted for genotyping. Information about relapses from 2 years before the start of treatment to either the end of treatment or the last follow-up visit was obtained from the Danish Multiple Sclerosis Treatment Register. Smoking information came from a comprehensive questionnaire., Results: We found that the relapse rate in patients with RRMS during IFN-β treatment was higher in smokers compared to nonsmokers, with an incidence rate ratio (IRR) of 1.20 (95% confidence interval [CI] 1.021-1.416, p = 0.027) and with an IRR increase of 27% per pack of cigarettes per day (IRR 1.27, 95% CI 1.056-1.537, p = 0.012). We found no association or interaction with HLA and the NAT1 variant., Conclusion: In this observational cohort study, we found that smoking is associated with increased relapse activity in patients with RRMS treated with IFN-β, but we found no association or interaction with HLA or the NAT1 variant., (© 2018 American Academy of Neurology.)

Background: Pediatric-onset multiple sclerosis (MS) affects life at a stage vital for social and educational achievements and psychiatric co-morbidity is common after MS onset. Few studies have examined psychiatric morbidity before MS onset., Methods: In this nationwide study, detailed case ascertainment was performed in all children with pediatric MS, including chart review. For each MS patient, we selected five controls using density sampling from the entire Danish population, matching controls to children with MS by sex and birthdate. We analyzed data as a nested case-control study with psychiatric morbidity as exposure and MS as outcome, and a matched cohort study with MS as exposure and psychiatric co-morbidity as outcome. Hazard ratios (HR) including 95% confidence intervals (CI) were estimated using Cox regression., Results: We identified 212 children with MS and 1060 controls. No association between psychiatric morbidity and the rate of MS was found before MS onset. After MS onset, children with MS had two times higher hazard for psychiatric co-morbidity compared with children without MS (HR=2.0; 95% CI=1.3-3.1; p<0.001)., Conclusion: Psychiatric morbidity seems to commence after MS onset, making screening for neuropsychiatric conditions pertinent in newly-diagnosed children with MS., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Objective: To investigate the effect of chronic comorbidity on the time of diagnosis of multiple sclerosis (MS) and on mortality in MS., Methods: We conducted a population-based, nationwide cohort study including all incident MS cases in Denmark with first MS symptom between 1980 and 2005. To investigate the time of diagnosis, we compared individuals with and without chronic comorbidity using multinomial logistic regression. To investigate mortality, we used Cox regression with time-dependent covariates, following study participants from clinical MS onset until endpoint (death) or to the end of the study, censuring at emigration., Results: We identified 8,947 individuals with clinical onset of MS between 1980 and 2005. In the study of time of diagnosis, we found statistically significant odds ratios for longer diagnostic delays with cerebrovascular comorbidity (2.01 [1.44-2.80]; <0.0005), cardiovascular comorbidity (4.04 [2.78-5.87]; <0.0005), lung comorbidity (1.93 [1.42-2.62]; <0.0005), diabetes comorbidity (1.78 [1.04-3.06]; 0.035), and cancer comorbidity (2.10 [1.20-3.67]; 0.009). In the mortality study, we found higher hazard ratios with psychiatric comorbidity (2.42 [1.67-3.01]; <0.0005), cerebrovascular comorbidity (2.47 [2.05-2.79]; <0.0005), cardiovascular comorbidity (1.68 [1.39-2.03]; <0.0005), lung comorbidity (1.23 [1.01-1.50]; 0.036), diabetes comorbidity (1.39 [1.05-1.85]; 0.021), cancer comorbidity (3.51 [2.94-4.19]; <0.0005), and Parkinson disease comorbidity (2.85 [1.34-6.06]; 0.007)., Conclusions: An increased awareness of both the necessity of neurologic evaluation of new neurologic symptoms in persons with preexisting chronic disease and of optimum treatment of comorbidity in MS is critical., (© 2017 American Academy of Neurology.)

Background: Lifetime expectancy in multiple sclerosis (MS) is reduced. Few studies have had sufficient follow-up or sufficient number of patients to assess if survival has improved with time. However, a recent meta-analysis found no time-dependent change in MS excess mortality across studies over recent decades., Objective: To investigate whether short-term all-cause excess mortality in patients with MS in the total Danish population has changed over the last six decades., Patients and Methods: We included all patients with MS recorded in the nationwide Danish MS Registry with definite or probable MS and onset from 1950 through 1999. The Danish Civil Registration System provided date of death for all deceased patients with follow-up in 2015, and Statistics Denmark supplied specific population mortality. We calculated excess number of death per 1000 person-years (EDR) and standardised mortality ratio (SMR)., Results: We included 18 847 patients among whom 6102 had died as opposed to 2492 expected deaths. EDR was 10.63 (95% CI 10.19 to 11.09) and a SMR was 2.45 (95% CI 2.39 to 2.51). The 15-year EDR dropped gradually from 11.29 (95% CI 9.95 to 12.73) in the 1950-1959 onset cohort to 2.56 (95% CI 1.98 to 3.18) in the 1990-1999 onset cohort, and SMR dropped from 4.48 (95% CI 4.06 to 4.92) to 1.80 (95% CI 1.62 to 1.99)., Conclusion: The decline in short-term excess mortality in MS started decades before disease-modifying treatment of MS became available, before use of MRI became widespread, and before the McDonald diagnostic criteria were introduced. A change in the MS cohorts with fewer malignant cases may be a significant contributor., Competing Interests: Competing interests: None declared., (© Article author(s) (or their employer(s) unless otherwise stated in the text of the article) 2017. All rights reserved. No commercial use is permitted unless otherwise expressly granted.)

Background: Little is known about the consequences of parental multiple sclerosis (MS) on offspring's socioeconomic circumstances., Objective: To investigate employment, disability pension and income in offspring of parents with MS compared with matched reference persons in a nationwide register-based cohort study., Methods: All Danish-born persons with onset of MS during 1950-1986 were retrieved from the Danish Multiple Sclerosis Registry. Their offspring were identified using the Civil Registration System. One random offspring from each sibship was matched by sex and year of birth with eight random reference persons., Results: We included 2456 MS offspring and 19,648 reference persons. At age 30, employment was lower among MS offspring than reference children (odds ratio (OR): 0.89; 95% confidence interval (CI): 0.84-0.95; p = 0.0003), and they more often received disability pension (OR: 1.31; 95% CI: 1.15-1.50; p < 0.0001) at ages 30 and 40 but not at age 50. Although the mean income was not significantly lower for the MS offspring cohort, most of them attained an annual personal income below 250,000 DKK (Danish krone), that is, ~33,650 EUR (OR: 0.91; 95% CI: 0.84-0.99; p = 0.04)., Conclusion: Having had a parent with MS may affect employment and increase the risk of disability pension and low income in adult life.

Background and Purpose: The social and economic consequences of comorbidity in multiple sclerosis (MS) are largely unexplored. Differences were investigated in income and in the rate of broken relationships between cases of MS with and without chronic comorbidity., Methods: We conducted a nationwide cohort study including all incident cases of MS in Denmark with clinical MS onset between 1980 and 2005. The difference in income was investigated at MS onset and 5 and 10 years after MS onset. The difference in the rate of broken relationships was investigated in subjects who were in a relationship at MS onset or who entered a relationship after MS onset. We used logistic, multiple linear and Poisson regression analyses., Results: Cases of MS with somatic comorbidity had increased odds of low incomes both 5 years {odds ratio (OR), 1.41 [95% confidence interval (CI), 1.19-1.67; P < 0.0005]} and 10 years [OR, 1.37 (95% CI, 1.17-1.60); P < 0.0005] after MS onset. The odds of a low income with psychiatric comorbidity was increased 10 years after MS onset [OR, 3.06 (95% CI, 1.47-6.37); P = 0.003]. The rate of broken relationships was increased in cases of MS with any somatic comorbidity [incidence rate ratio, 1.46 (95% CI, 1.32-1.61); P < 0.0005]., Conclusions: Our results underscore the burden of comorbidity in MS on patients, their partners and society., (© 2017 EAN.)

Few studies have addressed the possible association between age at menarche and multiple sclerosis (MS), and results are conflicting. We studied this issue in a large prospective cohort study. The study cohort comprised 77,330 women included in the Danish National Birth Cohort (1996-2002). Information on menarcheal age was ascertained at the first interview, which took place in the 16th week of pregnancy. Women were followed for MS from the first interview to December 31, 2011. Associations between age at menarche and risk of MS were evaluated with hazard ratios and 95% confidence intervals using Cox proportional hazards regression models. Overall, 226 women developed MS during an average follow-up period of 11.7 years. Age at menarche among women with MS was generally lower than that among women without MS (Wilcoxon rank-sum test; P = 0.002). We observed an inverse association between age at menarche and MS risk. For each 1-year increase in age at menarche, risk of MS was reduced by 13% (hazard ratio = 0.87, 95% confidence interval: 0.79, 0.96). Early age at menarche appears to be associated with an increased risk of MS. The mechanisms behind this association remain to be established., (© The Author 2017. Published by Oxford University Press on behalf of the Johns Hopkins Bloomberg School of Public Health. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

Background: Natalizumab and fingolimod were approved for treatment of active relapsing-remitting multiple sclerosis (RRMS) in Denmark in 2006 and 2011, respectively. There have been no randomized head-to-head studies comparing the two drugs., Objective: To compare the clinical efficacy of natalizumab and fingolimod., Methods: Data on all Danish RRMS patients who started their first second-line treatment with natalizumab or fingolimod from July 2011 to March 2015 were prospectively recorded in the Danish Multiple Sclerosis (MS) Treatment Register. The two treatment arms were 1:1 propensity score matched by baseline covariates using 'nearest neighbour' method., Results: Propensity score matching left 928 of 1309 RRMS cases, 464 in each treatment group. The on-treatment annualized relapse rate was 0.296 (95% confidence interval (CI): 0.26-0.34) for natalizumab and 0.307 (95% CI: 0.27-0.35) for fingolimod. The adjusted relapse rate ratio was 0.93 (95% CI: 0.74-1.17; p = 0.53). Mean time to first relapse was 2.55 and 2.56 years, respectively ( p = 0.76). There was no difference in change of Expanded Disability Status Scale (EDSS)., Conclusion: We found no differences in clinical disease activity between natalizumab- and fingolimod-treated RRMS patients in this real-life observational study. However, the lack of magnetic resonance imaging (MRI) data for the propensity score matching may conceal a higher efficacy of natalizumab.

Objective: As previous research has suggested that exposure to vitamin D insufficiency in utero may have relevance for the risk of multiple sclerosis (MS), we aimed to examine the direct association between level of neonatal vitamin D and risk of MS., Methods: We carried out a matched case-control study. Dried blood spots samples (DBSS) belonging to 521 patients with MS were identified in the Danish Newborn Screening Biobank. For every patient with MS, 1-2 controls with the same sex and birth date were retrieved from the Biobank (n = 972). Level of 25-hydroxyvitamin D (25[OH]D) in the DBSS was measured using liquid chromatography tandem mass spectroscopy. The association between different levels of 25(OH)D and risk of MS was evaluated by odds ratios (OR) calculated in conditional logistic regression models., Results: We observed that lower levels of 25(OH)D in neonates were associated with an increased risk of MS. In the analysis by quintiles, MS risk was highest among individuals in the bottom quintile (<20.7 nmol/L) and lowest among those in the top quintile of 25(OH)D (≥48.9 nmol/L), with an OR for top vs bottom of 0.53 (95% confidence interval [CI] 0.36-0.78). In the analysis treating 25(OH)D as a continuous variable, a 25 nmol/L increase in neonatal 25(OH)D resulted in a 30% reduced risk of MS (OR 0.70, 95% CI 0.57-0.84)., Conclusion: Low concentrations of neonatal vitamin D are associated with an increased risk of MS. In light of the high prevalence of vitamin D insufficiency among pregnant women, our observation may have importance for public health., (© 2016 American Academy of Neurology.)

To investigate the occurrence of vascular comorbidities before and after the clinical onset of multiple sclerosis. In this combined case-control and cohort study, all Danish born citizens with onset of multiple sclerosis 1980-2005 were identified from the Danish Multiple Sclerosis Registry and randomly matched with controls regarding year of birth, gender, and municipality on January 1st in the year of multiple sclerosis (MS) onset (index date). Individual-level information on comorbidities was obtained from several independent nationwide registries and linked to the study population by unique personal identification numbers. To assess the presence of vascular comorbidities before and after MS onset, cases and controls were followed from January 1977 to the index date, and from the index date through December 2012. We used logistic regression to calculate odds ratios (ORs) and Cox regression to calculate hazard ratios (HRs). Before the index date, MS cases had a decreased probability for cerebrovascular comorbidity [OR 0.69 (95 % CI 0.48-0.99, p = 0.043)], and a numerically but not statistically significant decreased probability for cardiovascular comorbidity [OR 0.87 (95 % CI 0.71-1.07, p = 0.188)]. After the index date, MS cases had an increased risk for cerebrovascular comorbidity [HR 1.84 (95 % CI 1.69-2.00, p < 0.0005)], and for cardiovascular comorbidity [HR 1.08 (95 % CI 1.02-1.15, p = 0.013)]. The lower occurrence of cerebrovascular comorbidities in cases prior to MS onset could be due to protective immune mechanisms, while the higher occurrence of vascular comorbidities in cases after MS onset could be because of converging causal pathways of the coexisting diseases. These findings deserve to be studied closer in a broader spectrum of comorbidities in MS.

Immunogenicity of biopharmaceutical products in multiple sclerosis is a frequent side effect which has a multifactorial etiology. Here we study associations between anti-drug antibody (ADA) occurrence and demographic and clinical factors. Retrospective data from routine ADA test laboratories in Sweden, Denmark, Austria and Germany (Dusseldorf group) and from one research study in Germany (Munich group) were gathered to build a collaborative multi-cohort dataset within the framework of the ABIRISK project. A subset of 5638 interferon-beta (IFNβ)-treated and 3440 natalizumab-treated patients having data on at least the first two years of treatment were eligible for interval-censored time-to-event analysis. In multivariate Cox regression, IFNβ-1a subcutaneous and IFNβ-1b subcutaneous treated patients were at higher risk of ADA occurrence compared to IFNβ-1a intramuscular-treated patients (pooled HR = 6.4, 95% CI 4.9-8.4 and pooled HR = 8.7, 95% CI 6.6-11.4 respectively). Patients older than 50 years at start of IFNβ therapy developed ADA more frequently than adult patients younger than 30 (pooled HR = 1.8, 95% CI 1.4-2.3). Men developed ADA more frequently than women (pooled HR = 1.3, 95% CI 1.1-1.6). Interestingly we observed that in Sweden and Germany, patients who started IFNβ in April were at higher risk of developing ADA (HR = 1.6, 95% CI 1.1-2.4 and HR = 2.4, 95% CI 1.5-3.9 respectively). This result is not confirmed in the other cohorts and warrants further investigations. Concerning natalizumab, patients older than 45 years had a higher ADA rate (pooled HR = 1.4, 95% CI 1.0-1.8) and women developed ADA more frequently than men (pooled HR = 1.4, 95% CI 1.0-2.0). We confirmed previously reported differences in immunogenicity of the different types of IFNβ. Differences in ADA occurrence by sex and age are reported here for the first time. These findings should be further investigated taking into account other exposures and biomarkers., Competing Interests: D. Bachelet, S. Hässler, C. Mbogning, J. Link, R. Ramanujam, M. Auer, P.E. Hyldgaard Jensen, K. Ingenhoven, D. Buck, V. Grummel, M. Pallardy, P. Dönnes, P. Broët: have nothing to declare. N. Koch-Henriksen has received honoraria for lecturing and participation in advisory councils, travel expenses for attending congresses and meetings, and financial support for monitoring the Danish Multiple Sclerosis Treatment Register from Bayer-Schering, MerckSerono, Biogen Idec, Teva, Sanofi-Aventis and Novartis. A. Fogdell-Hahn has received funding speaking honoraria from Biogen Idec and Pfizer. F. Deisenhammer participated in meetings sponsored by or received honoraria for acting as an advisor/speaker for Bayer Healthcare, Biogen Idec, Genzyme-Sanofi, Merck, Novartis Pharma, and Roche. C. Warnke participated in meetings sponsored by, or received honoraria for acting as an advisor/speaker for Bayer, Biogen, Novartis, and Teva. D. Buck has received compensation for activities with Bayer HealthCare, BiogenIdec, MerckSerono, and Novartis and she is supported by the Abirisk Consortium. H. Hartung has received honoraria for consulting, serving on steering committees and speaking from Biogen, GeNeuro, Genzyme, Merck, Novartis, Opexa, Receptos, Roche, Sanofi, Teva with approval by the president of Heinrich-Heine University. B. Kieseier has received honoraria for lecturing, travel expenses for attending meetings, and financial support for research from Bayer Health Care, Biogen Idec, Genzyme/Sanofi Aventis, Grifols, Merck Serono, Mitsubishi Europe, Novartis, Roche, Talecris, and TEVA. B. Hemmer has served on scientific advisory boards for Roche, Novartis, Bayer Schering, Merck Serono, Biogen Idec, GSK, Chugai Pharmaceuticals, Micromet, Genentech and Genzyme Corporation; serves on the international advisory board of Archives of Neurology and Experimental Neurology; has received speaker honoraria from Bayer Schering, Novartis, Biogen Idec, Merck Serono, Roche, and Teva Pharmaceutical Industries Ltd; and has received research support from Biogen Idec, Bayer Schering, Merck Serono, Five prime, Metanomics, Chugai Pharmaceuticals and Novartis. He has been filed a patent for the detection of antibodies and T cells against KIR4.1 in a subpopulation of MS patients and genetic determinants of neutralizing antibodies to interferon-beta. P.S. Sørensen has served on scientific advisory boards for Biogen Idec, Merck Serono, Novartis, Genzyme, Teva Pharmaceutical Industries Ltd., GlaxoSmithKline, medDay Pharmaceuticals and Forward Pharma; has been on steering committees or independent data monitoring boards in clinical trials sponsored by Merck Serono, Teva Pharmaceutical Industries Ltd., and GlaxoSmithKline; and has received speaker honoraria from Biogen Idec, Merck Serono, Teva Pharmaceutical Industries Ltd., Genzyme, and Novartis. His department has received research support from Biogen Idec, Bayer Schering, Merck Serono, TEVA, Baxter, Sanofi-Aventis, BioMS, Novartis, Bayer, RoFAR, Roche, Genzyme, from the Danish Multiple Sclerosis Society, the Danish Medical Research Council, and the European Union Sixth Framework Programme: Life sciences, Genomics and Biotechnology for health. M. Ryner has received research support from Biogen Idec and Sanofi-Aventis, and received speaker honoraria from Biogen Idec. Andy Lawton and Dan Sikkema are employed by GlaxoSmithKline. At the time of writing Julie Davidson was employed by and held stocks/shares in GlaxoSmithKline. Naoimh Donnellan is employed by IPSEN. Agnès Hincelin-Mery is employed by Sanofi. Pierre Dönnes is an employee of SciCross AB and has received support from the Innovative Medicines Initiative Joint Undertaking under grant agreement No. [115303], resources of which are composed of financial contribution from the European Union's Seventh Framework Program (FP7/2007–2013) and EFPIA companies' in kind contribution. All the company-employed authors declare that this does not alter their adherence to PLOS ONE policies on sharing data and materials.

Background: Inverse comorbidity is disease occurring at lower rates than expected among persons with a given index disease. The objective was to identify inverse comorbidity in MS., Methods: We performed a combined case-control and cohort study in a total nationwide cohort of cases with clinical onset of MS 1980-2005. We randomly matched each MS-case with five population controls. Comorbidity data were obtained from multiple, independent nationwide registries. Cases and controls were followed from January 1977 to the index date, and from the index date through December 2012. We controlled for false discovery rate and investigated each of eight pre-specified comorbidity categories: psychiatric, cerebrovascular, cardiovascular, lung, and autoimmune comorbidities, diabetes, cancer, and Parkinson's disease., Results: A total of 8947 MS-cases and 44,735 controls were eligible for inclusion. We found no inverse associations with MS before the index date. After the index date, we found a decreased occurrence of chronic lung disease (asthma and chronic obstructive pulmonary disease) (HR 0.80 (95% CI 0.75-0.86, p<0.00025)) and overall cancer (HR 0.88 (95% CI 0.81-0.95, p=0.0005)) among MS-cases., Conclusion: This study showed a decreased risk of cancers and pulmonary diseases after onset of MS. Identification of inverse comorbidity and of its underlying mechanisms may provide important new entry points into the understanding of MS., (Copyright © 2016 Elsevier B.V. All rights reserved.)

Little is known about the impact of parental multiple sclerosis (MS) on offspring's educational attainment. The objective of the study was to examine educational achievements in offspring of parents with MS compared with matched children of parents without MS in a nationwide register-based cohort study. Children of all Danish-born residents with onset between 1950 and 1986 were identified by linking the Danish Multiple Sclerosis Registry with the Civil Registration System. Twins, children with MS, and emigrated persons were excluded. The reference cohort consisted of randomly drawn individuals from the Civil Registration System without parental MS matched 8:1 to the MS offspring by sex and year of birth. Information about education was linked to the cohorts from nationwide educational registries. We included 4177 children of MS parents and 33,416 reference persons. Children of MS parents achieved statistically significant higher average grades than the reference cohort in their final exam of basic school with a mean grade difference of 0.46 (95 % CI 0.22-0.69; p = 0.0002). We found no difference in achievement of educational level above basic school (OR 1.04; 95 % CI 0.98-1.10; p = 0.20). There was a trend toward more MS offspring attaining health-related educations (OR 1.10; 95 % CI 1.00-1.21; p = 0.06). In conclusion, children of MS parents showed a small advantage in grade point average in final examinations in basic school, and they more often tended toward health-related educations. This study revealed no negative consequences of parental MS on grades and highest educational level achieved.

Aim of the Database: The Danish Multiple Sclerosis Treatment Register (DMSTR) serves as a clinical quality register, enabling the health authorities to monitor the quality of the disease-modifying treatment, and it is an important data source for epidemiological research., Study Population: The DMSTR includes all patients with multiple sclerosis who had been treated with disease-modifying drugs since 1996. At present, more than 8,400 patients have been registered in this database. Data are continuously entered online into a central database from all sites in Denmark at start and at regular visits., Main Variables: Include age, sex, onset year and year of the diagnosis, basic clinical information, and information about treatment, side effects, and relapses., Descriptive Data: Notification is done at treatment start, and thereafter at every scheduled clinical visit 3 months after treatment start, and thereafter every 6 months. The longitudinally collected information about the disease activity and side effects made it possible to investigate the clinical efficacy and adverse events of different disease-modifying therapies., Conclusion: The database contributed to a certain harmonization of treatment procedures in Denmark and will continue to be a major factor in terms of quality in clinical praxis, research and monitoring of adverse events, and plays an important role in research., Competing Interests: MM has served on scientific advisory board for Biogen Idec and Teva Pharmaceutical Industries Ltd.; has received honoraria for lecturing from Biogen Idec, Merck Serono, Novartis, Teva Pharmaceutical Industries Ltd.; has received support for congress participation from Biogen Idec, Teva Pharmaceutical Industries Ltd., Genzyme, and Novartis. NK-H has received honoraria for lecturing and participation in advisory councils, travel expenses for attending congresses and meetings from Bayer Schering Pharma AG, Merck Serono, Biogen Idec, Teva Pharmaceutical Industries Ltd., Sanofi-Aventis, and Novartis. PSS has served on scientific advisory boards for Biogen Idec, Merck Serono, Novartis, Genzyme, Teva Pharmaceutical Industries Ltd., GlaxoSmithKline, MedDay Pharmaceuticals, and Forward Pharma; has been on steering committees or independent data monitoring boards in clinical trials sponsored by Merck Serono, Teva Pharmaceutical Industries Ltd., and GlaxoSmithKline; and has received speaker honoraria from Biogen Idec, Merck Serono, Teva Pharmaceutical Industries Ltd., Genzyme, and Novartis. His department has received research support from Biogen Idec, Bayer Schering, Merck Serono, Teva Pharmaceutical Industries Ltd., Baxter, Sanofi-Aventis, BioMS, Novartis, Bayer, RoFAR, Roche, Genzyme, from the Danish Multiple Sclerosis Society, the Danish Medical Research Council, and the European Union Sixth Framework Programme: Life sciences, Genomics and Biotechnology for health. The authors report no other conflicts of interest in this work.

Background: It has been suggested that onset of multiple sclerosis (MS) is preceded by a clinically silent period of up to 10 years., Objectives: Examine whether such a period should be associated with poor self-rated health (SRH)., Methods: Information on SRH before pregnancy was ascertained among 80,848 women participating in the Danish National Birth Cohort (DNBC) 1996-2002. Women were followed for MS from enrolment in DNBC in the 16th week of pregnancy until 31 December 2011. Associations between SRH and MS were evaluated by means of hazard ratios (HR) with 95% confidence intervals (CIs) using Cox proportional hazard models., Results: During on average 11.7 years of follow-up, 239 women were diagnosed with MS. Overall, neither women with fair (HR = 1.09 (95% CI = 0.83-1.41), n = 113) nor poor pre-pregnancy SRH (HR = 0.94 (95% CI = 0.47-1.87), n = 9) were at an increased risk of MS compared with women reporting very good pre-pregnancy SRH. Supplementary analyses showed no significant differences in MS risk in consecutive periods of follow-up., Conclusion: In this first prospective cohort study assessing MS risk as a function of SRH, we found no indication of a long period of poor SRH prior to MS. Our findings based on pregnant women may not necessarily apply to all women., (© The Author(s), 2015.)

Background: Evidence is accumulating supporting a beneficial effect of vitamin D in multiple sclerosis (MS). Genome-wide association studies (GWAS) have shown significant associations between 25-hydroxyvitamin D (25(OH)D) and single nucleotide polymorphisms (SNPs) in key genes in the vitamin D metabolism., Objective: To examine the association between 25(OH)D and six GWAS SNPs and environmental factors in 1497 MS patients., Methods: Blood samples and lifestyle questionnaires were collected between 2009 and 2012. Genotyping of GC-, CYP2R1- and NADSYN1-SNPs was performed by TaqMan allelic discrimination (Life Technologies)., Results: We found significant associations between 25(OH)D and SNPs in GC (rs7041, p = 0.01 and rs2282679, p = 0.03) and CYP2R1 (rs10741657, p =1.8 × 10(-4)). Season of blood sampling (p = 2.8 × 10(-31)), sex (p = 1.9 × 10(-5)), BMI (p = 2.3 × 10(-5)), vitamin supplements (p = 7.0 × 10(-22)), and fish intake (p = 0.02) also had significant effects on 25(OH)D., Conclusion: In this cross-sectional study, we found significant effects of environmental factors and SNPs in GC and CYP2R1 on 25(OH)D in MS patients. Since 25(OH)D might have protective effects in MS, and vitamin D supply is a modifiable factor, it may be important to include this in the MS treatment regimen., (© The Author(s), 2014.)

Background: Animal studies have suggested that drugs inhibiting the enzyme histone deacetylase might have a beneficial effect on multiple sclerosis (MS). Valproic acid (VPA), an anti-epileptic drug, is the only widely used human drug with a histone deacetylase inhibitory effect., Objective: The objective of this paper is to examine if VPA use is associated with a reduced risk of MS., Methods: We conducted a propensity score-matched cohort study in the period 1997-2011 linking nationwide register data on filled VPA prescriptions, MS cases, and several covariates. The VPA users were matched on propensity scores in a 1:4 ratio with non-users of VPA. Incidence rates of MS were compared among VPA users and non-users of VPA using Cox regression to estimate hazard ratios (HRs)., Results: Among 16 028 ever-users of VPA and 54 172 non-users, 18 and 26 cases of MS were identified, respectively. Neither current VPA users nor recent users of VPA, who had ceased VPA treatment within the last year, were at a reduced risk of MS compared with non-users of VPA (HR = 1.30 (95% confidence interval, 0.44-3.80), n = 4, and HR = 1.22 (0.28-5.32), n = 2, respectively). Similarly, in an intention-to-treat analysis, ever-users of VPA were not at reduced risk of MS (HR = 2.41 (1.32-4.43), n = 18)., Conclusion: In the first human study addressing a possible beneficial effect of VPA use on the risk of MS, we found no support for a protective effect. However, given the wide confidence intervals, only large effects can be ruled out with sufficient certainty., (Copyright © 2014 John Wiley & Sons, Ltd.)

There are two nationwide population-based registers for multiple sclerosis (MS) in Denmark. The oldest register is The Danish Multiple Sclerosis Registry (DMSR), which is an epidemiological register for estimation of prevalence and incidence of MS and survival, and for identifying exposures earlier in life that may affect the risk of MS. This register has no systematic follow-up data except for survival. The DMSR has over the years published nationwide incidence- and prevalence data from Denmark and has been involved in a number of 'historical prospective' studies to elucidate the association between a number of different environmental exposures in the past and the subsequent risk of MS. Some of these studies have been able to exonerate suspected risk factors. The other register, the nationwide Danish Multiple Sclerosis Treatment Register, is a follow-up register for all patients who have received disease-modifying treatments since 1996. It has, in particular, contributed to the knowledge of the role of antibodies against the biological drugs used for the treatment of MS., (© 2015 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

Background: Gender appears to play a role in incidence and disease course of multiple sclerosis (MS)., Objective: The objective was to determine whether male and female patients with MS respond differently to interferon-beta treatment in terms of reduction in relapse rates., Methods: We included all 2033 patients with relapsing-remitting MS who started treatment with interferon-beta from 1996 to 2003, identified from the Danish Multiple Sclerosis Treatment Register. We defined neutralizing antibody (NAb)-positive and NAb-negative periods in the single patient by the results of the NAb tests. Patients served as their own controls, and relapse rates were compared between NAb-negative and NAb-positive periods., Results: NAbs significantly abrogated the interferon-beta treatment efficacy in both genders. The all-over women:men relapse rate ratio irrespective of NAb status was 1.47 (95%CI; 1.28-1.68). In a generalized linear Poisson models analysis with relapse counts as response variable, the main effects NAbs, sex, age at treatment start and number of relapses in 2 years before treatment start were strongly significant, but the effect of NAbs on relapse rates did not differ significantly between men and women., Conclusion: As NAbs influenced the on-treatment relapse rates strongly in both sexes but without statistical significant difference, there is no indication of different effects of interferon-beta in men or women., (© 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

Objective: Single nucleotide polymorphisms (SNPs) in the genes encoding interferon response factor (IRF)-5, IRF-8 and glypican-5 (GPC5) have been associated with disease activity in multiple sclerosis (MS) patients treated with interferon (IFN)-β. We analysed whether SNPs in the IRF5, IRF8 and GPC5 genes are associated with clinical disease activity in MS patients beginning de novo treatment with IFN-β., Methods: The SNPs rs2004640, rs3807306 and rs4728142 in IRF5, rs13333054 and rs17445836 in IRF8 and rs10492503 in GPC5 were genotyped in 575 patients with relapsing-remitting MS followed prospectively after the initiation of their first treatment with IFN-β., Results: 62% of patients experienced relapses during the first 2 years of treatment, and 32% had disability progression during the first 5 years of treatment. Patients with a pretreatment annualized relapse rate >1 had an increased risk of relapse (hazard ratio 1.53, 95% confidence interval 1.24-1.90) and progression (hazard ratio 1.48, 95% confidence interval 1.10-1.99) on treatment and patients with breakthrough relapses in the form of relapses during the first 2 years of treatment had an increased risk of progression during the first 5 years of treatment (hazard ratio 2.04, 95% confidence interval 1.47-2.85).The gene variants in IRF5, IRF8 and GPC5 were not associated with risk of relapse or disease progression., Conclusions: Pretreatment relapse rate and clinical disease activity during the first 2 years of treatment may be associated with disease progression in MS patients treated with IFN-β. Genetic analysis of the studied gene variants do not provide additional information., (© 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

Background: Identification of MS registries and databases that are currently in use in Europe as well as a detailed knowledge of their content and structure is important in order to facilitate comprehensive analysis and comparison of data., Methods: National MS registries or databases were identified by literature search, from the results of the MS Barometer 2011 and by asking 33 national MS societies. A standardized questionnaire was developed and sent to the registries' leaders, followed by telephone interviews with them., Results: Twenty registries were identified, with 13 completing the questionnaire and seven being interviewed by telephone. These registries differed widely for objectives, structure, collected data, and for patients and centres included. Despite this heterogeneity, common objectives of the registries were epidemiology (n=10), long-term therapy outcome (n=8), healthcare research (n=9) and support/basis for clinical trials (n=8). While physician-based outcome measures (EDSS) are used in all registries, data from patients' perspectives were only collected in six registries., Conclusions: The detailed information on a large number of national MS registries in Europe is a prerequisite to facilitating harmonized integration of existing data from MS registries and databases, as well as comprehensive analyses and comparison across European populations., (© The Author(s), 2014.)

Background: Current knowledge concerning the association between exposure to stressful life-events (SFLEs) in childhood and later risk of multiple sclerosis (MS) is sparse., Objectives: We studied the associations between SFLEs in childhood and subsequent risk of MS in a nationwide cohort of 2.9 million Danes born from 1968 to 2011., Methods: A SFLE in childhood was defined as exposure before age 18 years to parental divorce, parental death, or death of a sibling, using information from the Danish Civil Registration System. MS cases in the cohort were identified in the Danish Multiple Sclerosis Registry. Associations of SFLE with MS risk were evaluated by incidence rate ratios (RR) of MS obtained in log-linear Poisson regression models., Results: Persons exposed to any SFLE in childhood were at 11% elevated risk of MS (RR = 1.11; 95% confidence interval: 1.03-1.20), compared to non-exposed persons. Stratification by subtype of SFLE showed that parental death and death of a sibling were not associated with MS risk. However, persons exposed to parental divorce were at 13% increased risk of developing MS compared to non-exposed (RR = 1.13; 1.04-1.23)., Conclusions: Associations of SFLEs in childhood with risk of MS are weak. However, parental divorce is somehow associated with modestly increased risk of MS., (© The Author(s), 2014.)

Objective: It is unclear whether psychological stress is associated with increased risk of multiple sclerosis (MS). We studied the association between major stressful life events and MS in a nationwide cohort study using death of a child or a spouse or marital dissolution as indicators of severe stress., Methods: We created two study cohorts based on all Danish men and women born 1950-1992. One cohort consisted of all persons who became parents between 1968 and 2010, and another cohort consisted of all persons who married between 1968 and 2010. Members of both cohorts were followed for MS between 1982 and 2010 using data from the National Multiple Sclerosis Registry. Associations between major stressful life events and risk of MS were evaluated by means of MS incidence rate ratios (RR) with 95% confidence interval (CI) obtained in Poisson regression analyses., Results: During approximately 30 million person-years of follow-up, bereaved parents experienced no unusual risk of MS compared with parents who did not lose a child (RR=1.12 (95% CI 0.89 to 1.38)). Likewise, neither divorced (RR=0.98 (95% CI 0.89 to 1.06)) nor widowed (RR=0.98 (95% CI 0.71 to 1.32) persons were at any unusual risk of MS compared with married persons of the same sex., Conclusions: Our national cohort study provides little evidence for a causal association between major stressful life events (as exemplified by divorce or the loss of a child or a spouse) and subsequent MS risk., (Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://group.bmj.com/group/rights-licensing/permissions.)

Background: The incidence of multiple sclerosis (MS) in Denmark has doubled in women since 1970, whereas it has been almost unchanged in men. The rapid epidemiological changes suggest that environmental factors may modify the risk of MS., Objectives: To investigate whether occupational, physical, or social environmental influence the risk of MS differently in women than in men., Methods: The cohort consists of all 1403 patients (939 women, 464 men) identified through Danish Multiple Sclerosis Registry aged 1-55 of years at clinical onset between 2000 and 2004, and up to 25 control persons for each case, matched by sex, year of birth and residential municipality. The same cohort was previously used to investigate the influence of the reproductive factors on the risk of MS., Results: By linkage to Danish population registers we found a slight albeit statistically significant excess for 6 female MS patients who had been employed in agriculture: OR 3.52; 95% CI 1.38-9.00, p=0.008 (0.046 when corrected for multiple significance) and a trend for exposure to outdoor work in 12 : OR 1.94, 95% CI 1.06-3.55, p=0.03 (0.09 when corrected for multiple significance), but the numbers of cases were small, and the effects were not found in men. Educational level, housing conditions in youth, or the presence of children unrelated by blood in the household did not influence the risk of MS., Conclusions: Our study did not reveal any additional factors beyond the previously published childbirths which could explain the extent of the MS incidence increase in women., (Copyright © 2014 Elsevier B.V. All rights reserved.)

Background: The female preponderance in incidence of multiple sclerosis (MS) calls for investigations into sex differences in comorbidity with other autoimmune diseases (ADs)., Objectives: To determine whether male and female patients with MS have a higher frequency of autoimmune comorbidity than controls, and to describe the type and frequency of ADs that are associated with MS., Methods: Our database was established by linkage of the Danish MS Registry to The Danish National Patient Register and consisted of 1403 patients of both sexes with clinical onset of MS between 2000 and 2004, and 25 matched controls for every case., Results: None of the ADs occurred more frequently in female cases than in controls. Male cases were more likely to have Type I diabetes mellitus (odds ratio (OR) = 3.34; 95% CI 1.40 - 7.02; p < 0.008), Crohn's disease (OR = 5.03; 95% CI 1.18 - 16.10; p = 0.03) and systemic lupus erythematosus (OR = 12.55; 95% CI 1.62 - 69.95; p = 0.02) than male controls., Conclusions: Autoimmune disorders are rare, but some of them tend to occur together with MS at a higher rate than in controls. Although women are generally more prone to ADs than men, significantly increased occurrence of other ADs were only found in male MS patients., (© The Author(s) 2014.)

A number of studies have reported flare-up of multiple sclerosis (MS) disease activity after cessation of natalizumab, increasing to a level beyond the pre-natalizumab treatment level. Our aim was to describe the development in clinical disease activity following cessation of natalizumab therapy in a large unselected cohort of highly active patients. We studied 375 highly active patients who had suffered at least two significant relapses within 1 year or three relapses within 2 years, or had been treated with mitoxantrone for highly active disease. All patients had discontinued therapy with natalizumab after at least 24 weeks on therapy, and had been followed 3-12 months (mean 8.9 months) after cessation of natalizumab therapy. The annualised relapse rate before start of natalizumab therapy was 0.94 (95 % confidence interval [CI] 0.88-1.00), 0.47 (95 % CI 0.43-0.52) during natalizumab therapy, 0.63 (95 % CI 0.51-0.76) 1-6 months after natalizumab and 0.55 (95 % CI 0.42-0.70) 7-12 months after natalizumab. However, 83 (22 %) of the patients could be classified as showing rebound of relapses, defined as a higher individual relapse rate after cessation of natalizumab than before natalizumab. These patients had a higher annualised relapse rate during natalizumab therapy. For the whole patient group, the relapse rate after discontinuation did not exceed the pre-natalizumab relapse rate at any time, but 22 % of the patients showed rebound of relapses after discontinuation of natalizumab.

Background and Purpose: Case reports have observed a co-occurrence of multiple sclerosis (MS) and Parkinson's disease (PD) and it has been hypothesized that MS lesions could affect dopaminergic pathways causing parkinsonism. Our aim was to examine the association between MS and PD in a historically prospective cohort study using Danish nationwide register data., Methods: Multiple sclerosis patients identified in the Multiple Sclerosis Registry were followed for PD from 1977 to 2011 in the National Patient Register. As measures of relative risk, ratios of observed to expected incidence rates of first hospitalization for PD amongst persons with MS were used, i.e. standardized incidence ratios (SIRs) with 95% confidence intervals (CIs)., Results: Amongst 15,557 MS patients 26 cases of PD were observed versus 26.51 expected, reflecting no overall increased risk of PD (SIR 0.98, 95% CI 0.67-1.44). Similar estimates were seen for female (SIR 0.99, 95% CI 0.58-1.67) and male MS patients (SIR 0.97, 95% CI 0.55-1.72). Likewise, no increased risk of PD amongst MS patients was observed in a robustness analysis backdating the date of diagnosis of PD by 5 years to account for the time lag between disease onset and first hospital contact with PD (SIR 0.57, 95% CI 0.32-1.00)., Conclusion: Our data do not suggest an increased risk of PD amongst patients with MS., (© 2013 The Author(s) European Journal of Neurology © 2013 EFNS.)

Background: The incidence of multiple sclerosis (MS) in Denmark has doubled in women since 1970, whereas it has been almost unchanged in men., Objectives: To investigate whether age at first childbirth and number of births have an effect on the risk of developing MS., Methods: The cohort consisted of 1403 patients with MS of both sexes, identified through the Danish Multiple Sclerosis Registry, with clinical onset between 2000 and 2004. For each case, 25 control persons were drawn by random from the Danish Civil Registration System matched by sex, year of birth, and residential municipality., Results: More female cases than controls had no childbirths or fewer births before clinical onset (p=0.018) but only in the last five years preceding onset (p<0.0001). Childbirths within five years before clinical onset reduced the risk of MS onset in women: OR=0.54 (95% CI 0.41-0.70, p<0.0001) for one child and OR=0.68 (95% CI 0.53-0.87, p=0.002) for more than one child. Parental age at first childbirth had no effect on the risk of MS., Conclusions: The data did not suggest reversed causality between childbirth and MS.

Background: Apart from a recent study reporting a 2- to 3-fold increased risk of multiple sclerosis (MS) among women and men who were delivered by Cesarean section (C-section), little attention has been given to the possible association between mode of delivery and the risk of MS., Objectives: We studied the association between C-section and risk of MS, in a cohort of 1.7 million Danes born from 1973 to 2005., Methods: Information on C-section and MS was obtained from the Danish Medical Birth Register and the Danish MS Register, respectively. The association between C-section and MS was evaluated by means of MS incidence rate ratios (RR) with 95% confidence intervals (CI) obtained in log-linear Poisson regression analyses., Results: There were 930 cases of MS in the study cohort, of whom 80 (9%) were delivered by C-section. Overall, we found there was no significant association between C-section and risk of MS (RR = 1.17; 0.92-1.46). Analyses stratified by sex revealed no unusual risk of MS for women (RR = 1.08: 0.80-1.42) nor men (RR = 1.37: 0.91-1.98). A supplementary sibling-matched Cox regression analysis likewise suggested there was no excess risk of MS in persons delivered by C-section (HR = 1.03; 0.63-1.69)., Conclusions: Mode of delivery appears to be unimportant in relation to MS development in the offspring.

Background: Obesity in late adolescence has been associated with an increased risk of multiple sclerosis (MS); however, it is not known if body size in childhood is associated with MS risk., Methods: Using a prospective design we examined whether body mass index (BMI) at ages 7-13 years was associated with MS risk among 302,043 individuals in the Copenhagen School Health Records Register (CSHRR). Linking the CSHRR with the Danish MS registry yielded 774 MS cases (501 girls, 273 boys). We used Cox proportional hazards models to estimate the hazard ratios (HRs) and 95% confidence intervals (CIs)., Results: Among girls, at each age 7-13 years, a one-unit increase in BMI z-score was associated with an increased risk of MS (HR(age 7)=1.20, 95% CI: 1.10-1.30; HR(age 13)=1.18, 95% CI: 1.08-1.28). Girls who were ≥95(th) percentile for BMI had a 1.61-1.95-fold increased risk of MS as compared to girls <85(th) percentile. The associations were attenuated in boys. The pooled HR for a one-unit increase in BMI z-score at age 7 years was 1.17 (95% CI: 1.09-1.26) and at age 13 years was 1.15 (95% CI: 1.07-1.24)., Conclusion: Having a high BMI in early life is a risk factor for MS, but the mechanisms underlying the association remain to be elucidated.

Background and Purpose: The Evidence-Based Decision Support Tool in Multiple Sclerosis (EBDiMS) is the first web-based prognostic calculator in multiple sclerosis (MS) capable of delivering individualized estimates of disease progression. It has recently been extended to provide long-term predictions based on the data from a large natural history cohort., Methods: We compared the predictive accuracy and consistency of EBDiMS with that of 17 neurologists highly specialized in MS., Results: We show that whilst the predictive accuracy was similar, neurologists showed a significant intra-rater and inter-rater variability., Conclusions: Because EBDiMS was consistent, it is of superior utility in a specialist setting. Further field testing of EBDiMS in non-specialist settings, and investigation of its usefulness for counselling patients in treatment decisions, is warranted., (© 2012 The Author(s) European Journal of Neurology © 2012 EFNS.)

Background: In a subgroup of patients with multiple sclerosis natalizumab therapy causes generation of anti-natalizumab antibodies that may be transient or persistent. It is recommended to discontinue natalizumab therapy in persistently antibody-positive patients., Objective: To use titres of anti-natalizumab antibodies to predict persistency of antibodies., Patients and Methods: In 525 consecutive natalizumab treated patients tested for anti-natalizumab antibodies 43 (8.2%) were antibody-positive. Thirty of the antibody-positive patients, who were tested both at three and at six months after treatment start, had antibody titres in blood measured using an extended ELISA method., Results: Samples from persistently positive patients ( N =18) had higher titre values than samples from transiently positive patients ( N =12). A cut-off value for high titre values was generated, above which patients may discontinue natalizumab therapy after three months. The method had a sensitivity of 0.83, a specificity of 1.00 and a diagnostic accuracy of 0.90., Conclusion: An extended ELISA method for measuring anti-natalizumab antibody titres in multiple sclerosis patients on natalizumab therapy may be used for evaluation of antibody persistence. A test at three months may identify patients with high titres, who should discontinue natalizumab therapy, and patients with transient low-titre antibodies, who may continue natalizumab therapy despite development of antibodies.

Background: Patients with multiple sclerosis (MS) are potentially at high risk of fracture due to falls and osteoporosis., Objective: To estimate incidence rates of fractures in MS patients, stratified by fracture type, sex and age, and to compare these rates with controls., Methods: The case population consisted of all patients with an accepted diagnosis of MS in the Danish MS Registry (1949-2007). Data were linked to the National Hospital Discharge Register (1977-2007). Patients with MS (n = 11,157) were 1:6 matched by year of birth, gender, calendar time and region to persons without MS (controls). Incidence rates of fracture were estimated as the number of fractures per 1000 person-years. Incidence rate ratios (IRRs) were calculated by dividing fracture rates in MS patients by fracture rates in controls., Results: Among patients with MS, the incidence rate of any fracture yielded 22.8 per 1000 person-years. The IRR of any fracture between MS patients and controls was 1.40 (95% CI 1.33-1.46). In particular, IRRs of tibia fracture (3.36 [2.75-4.11]), femur fracture (6.66 [5.06-8.76]) and hip fracture (3.20 [2.83-3.62]) were elevated in MS patients versus controls., Conclusion: Fractures occurred more often in patients with MS, especially fractures of the tibia, hip and femur.

Background: The Danish National Patient Register, Landspatientregistret (LPR), is a register of all hospital discharges and outpatient treatments in Denmark., Aims: It is increasingly used in research so it is important to understand to what extent this can be used as an accurate source of information. Virtually all patients in Denmark with multiple sclerosis (MS) are reported to the Combined MS Registry (DMSR), so this was used as the standard which the LPR was compared against., Methods: All residents of Denmark are assigned a unique Civil Register (CPR) number; this was used to compare data between registers. The LPR completeness was estimated by the proportion of cases from the DMSR that could be retrieved from the LPR. The LPR validity was estimated by the proportion of cases, listed in the LPR and DMSR, in whom the MS diagnosis could be confirmed as definite/probable/possible by the DMSR., Results: We found that 86.9% of those who were DMSR listed with an approved MS diagnosis were also listed in the LPR with a MS diagnosis. The diagnosis was valid in 96.3% of patients listed in the LPR when compared against the DMSR., Conclusions: The low completeness reduces the usefulness of the LPR in epidemiological MS research, in particular incidence studies. The study also found that the completeness of the LPR could be increased to 92.8% by including LPR records from other departments in addition, but this reduced the validity of the LPR to 95.1%. However, these results cannot uncritically be applied to registration of other diseases in the LPR., (© 2011 John Wiley & Sons A/S.)

The traditional view, based on numerous early studies and reviews, is that MS is particularly prevalent in temperate zones both on the northern and southern hemisphere. This uneven distribution of MS can be attributed to differences in genes and environment and their interaction. Diagnostic accuracy and case ascertainment are sources of error and have their shares in the geographical and temporal variations, and improvements in diagnostic accuracy and case ascertainment influence incidence- and prevalence rates. In addition the prevalence also depends on survival. With this meta-analysis we have focused on the trend in the incidence and sex ratio of MS through the last five decades, and we have analyzed the latitudinal distribution of MS incidence, based on a recent literature search. Our findings indicated that the prevalence and incidence rates had increased in almost all areas, but the previously reported latitudinal gradient of incidence of MS in Europe and North America could not be confirmed even when restricting the search to surveys published before 1980 or 1970. Conversely, the latitudinal gradient of prevalence rates seemed to be preserved. This apparent discrepancy can be explained by the circumstance that incidence estimates only depend on complete ascertainment for a relative short recent period of time, whereas reliable prevalence rates presuppose complete ascertainment decades back in time. A contributory explanation for the missing latitudinal gradient for incidence may be changes in environmental factors, levelling out differences in habits of life across Europe and North America, and, not least, that the interpretation of a latitudinal gradient in Europe was based primarily on prevalence studies and reviews. In addition, we observed in most regions a profound increase in female incidence of MS. The last observation should prompt epidemiological studies focusing on change in female life style., (Copyright © 2011 Elsevier B.V. All rights reserved.)

Background: In the clinical trials about 9% of natalizumab treated multiple sclerosis (MS) patients generated anti-natalizumab antibodies, of which 6% were persistent and 3% transient. The occurrence of antibodies reduced serum levels of natalizumab, decreased bio-efficacy, and abrogated the therapeutic efficacy., Objective: The objective was to assess the frequency of anti-natalizumab antibodies in an unselected cohort of patients from four different countries., Methods: We measured anti-natalizumab antibodies in a large cohort of 4881 unselected patients from four MS centres that systematically measured antibodies in patients treated with natalizumab. We applied the same ELISA assay developed by Biogen Idec and used in the pivotal trials of natalizumab., Results: Antibodies occurred in 4.5% (95% confidence interval, CI: 4.0-5.1%) of the patients, and were persistent in 3.5% (95% CI: 3.0-4.0%) and transient in 1.0% (95% CI: 0.7-1.3%) of the patients. The frequencies of permanently antibody positive patients did not show statistically significant differences between the four centres, whereas the frequencies of transiently antibody positive patients showed some variations., Conclusion: The frequencies of antibodies appeared to be of the same magnitude in the four centres, but might be less than in the pivotal studies of natalizumab.

Introduction: The Danish Multiple Sclerosis (MS) Registry was established in 1956., Content: The register comprises data on all Danes who had MS in 1949 or who have been diagnosed since. Data on new cases and updated information on persons with an MS diagnosis already notified are continuously collected and classified according to standardized diagnostic criteria., Validity and Coverage: The completeness and validity is high (91% and 94%, respectively)., Conclusion: In January 2005 the register included data on 20,652 persons with a valid MS diagnosis, of whom 9,377 were alive. The register is the only existing nationwide MS register and covers a period of more than 50 years.

Introduction: This paper reviews the most important articles using data from the Danish Multiple Sclerosis Registry (DMSR) published in the past 25 years., Research Topics: These articles include: descriptive epidemiological studies, indicating that the female incidence of multiple sclerosis (MS) in Denmark has increased considerably; follow-up studies on social events, showing that patients at a high rate lose their working ability and their spouses/partners; mortality studies, demonstrating a considerable excess mortality; cause-of-death studies; comorbidity studies; and, most importantly, historical prospective studies identifying some risk factors (e.g. infectious mononucleosis) and refuting others (head trauma and a number of occupational exposures e.g. nurses, utility workers, people exposed to solvents). The most important results are briefly presented., Conclusion: The Danish MS register has proven to be a valuable tool for MS epidemiology and has provided knowledge that could not otherwise be achieved.