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Introduction: Bacillus Calmette–Guérin (BCG) vaccination induces long-lasting effects on the adaptive and innate immune systems and prevents development of experimental autoimmune encephalomyelitis and possibly also inflammatory disease activity in multiple sclerosis (MS). Objective: The objective is to examine if BCG given in early adulthood decreases MS risk. Methods: From 791,369 (52% females) Norwegians participating in a national tuberculosis screening program from 1963 to 1975, we collected information on BCG vaccination and tuberculosis disease status. Later, MS disease was ascertained through both the Norwegian MS Registry and Biobank and the Norwegian Death Registry. We used logistic regression models to assess the relationship between BCG vaccination and MS risk. Results: In those BCG vaccinated, mean age at vaccination was 15.6 (standard deviation (SD) = 5.5) years. A total of 2862 (65% females) MS cases were retrieved. Overall, we found no association between MS risk and BCG vaccination. Compared to non-BCG-vaccinated individuals with no signs of tuberculosis infection, odds ratio (OR) for MS was 1.00 (95% confidence interval (CI) = 0.80–1.25) in the BCG-vaccinated group. In those not BCG vaccinated because of latent tuberculosis infection, the corresponding OR was 0.86 (95% CI = 0.66–1.13). Conclusion: We found no evidence of BCG vaccination or latent tuberculosis infection in young adulthood being linked to MS risk. [ABSTRACT FROM AUTHOR]

To assess the temporal relationship between premorbid lipid levels and long-term amyotrophic lateral sclerosis (ALS) risk. From Norwegian cardiovascular health surveys (1974–2003), we collected information on total cholesterol (TC), triglycerides (TG), high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), glucose, and other cardiovascular risk factors. ALS incidence and mortality were identified through validated Norwegian health registries. The relation between premorbid lipid levels and ALS risk was assessed by Cox regression models. Out of 640,066 study participants (51.5% females), 974 individuals (43.5% females) developed ALS. Mean follow-up time was 23.7 (SD 7.1) years among ALS cases. One mmol/l increase in LDL-C was associated with 6% increase in risk for ALS (hazard ratio 1.06 [95% CI: 1.01–1.09]). Higher levels of TC and TG were also associated with increased ALS risk, but only within the last 6–7 years prior to ALS diagnosis or death. No association between HDL-C and ALS risk was found. Adjusting for body mass index, birth cohort, smoking, and physical activity did not alter the results. Higher levels of LDL-C are associated with increased ALS risk over 40 years later, compatible with a causal relationship. The temporal relationship between TG, TC, and ALS risk suggests that increased levels of these lipid biomarkers represent consequences of ALS. [ABSTRACT FROM AUTHOR]

Increasing female: male ratio in multiple sclerosis (MS) has been assigned to cohort effects, with females in more recent birth cohorts possibly being more exposed or vulnerable to environmental risk factors than males. We collected MS mortality data in Norway from 1951 to 2015 from The Norwegian Cause of Death registry. Age-Period-Cohort analysis was conducted using log-linear Poisson models, including sex interaction terms. MS was registered as the underlying, contributing or direct cause in 6060 deaths. MS associated mortality remained stable with a slight preponderance among males until after 1980, and have since increased preferentially among females. Throughout the study period the mean annual increase was 1.25% for females and 0.3% for males (p < 0.0001). Age-period-cohort analysis revealed limited evidence of cohort effects for the gender differences; the best fitting model only included gender-age and gender-period interaction terms. The period effect evened out for males in the last three decades but increased for females, especially among the oldest age-groups. In conclusion, the increased female: male mortality ratio in MS associated mortality is driven mainly by increased mortality among females in the three last decades, particularly in the older age groups. It is best explained by disproportional period effects, providing evidence of time-varying external factors including improved access to diagnosis among females. [ABSTRACT FROM AUTHOR]

Objective: In Norway, diagnoses from specialist health care visits, drug prescriptions, and causes of deaths are registered in compulsory health registers. We aimed to determine amyotrophic lateral sclerosis (ALS) prevalence from 2009 to 2015 by combining these registers. Methods: We validated the Norwegian Patient Registry (NPR) through hospital files, and linked it with the Norwegian Cause of Death Registry and the Norwegian Prescription Database. Poisson regression models were fitted for estimating gender ratios, time trends and possible interactions. Similar models were used for mortality data subtracted from the dataset. Results: Eleven percent of patients with at least one ALS-related entry in NPR did not have ALS. ALS prevalence could nevertheless be reliably estimated through ascertaining cases identified in two separate registers, or with at least two entries in NPR with first entry within four years prior to prevalence date. ALS prevalence remained stable, and was 7.6/100,000 (95% CI 6.9-8.4) at 31st December 2015. Mean male:female ratio was higher for prevalence (1.8; 95% CI 1.6-2.0) than for mortality (1.5; 95% CI 1.2-1.8) (p = 0.04). There were also significant regional differences in prevalence (p < 0.01) but not in mortality. Conclusions: Norwegian compulsory health registers provide reliable tools for ALS surveillance, and suggest gender and regional differences in survival after diagnosis. [ABSTRACT FROM AUTHOR]

Background: Results from previous studies on a possible interaction between smoking and Epstein–Barr virus (EBV) in the risk of multiple sclerosis (MS) are conflicting. Objectives: To examine the interaction between smoking and infectious mononucleosis (IM) in the risk of MS. Methods: Within the case–control study on Environmental Factors In Multiple Sclerosis (EnvIMS), 1904 MS patients and 3694 population-based frequency-matched healthy controls from Norway, Italy, and Sweden reported on prior exposure to smoking and history of IM. We examined the interaction between the two exposures on the additive and multiplicative scale. Results: Smoking and IM were each found to be associated with an increased MS risk in all three countries, and there was a negative multiplicative interaction between the two exposures in each country separately as well as in the pooled analysis (p = 0.001). Among those who reported IM, there was no increased risk associated with smoking (odds ratio (OR): 0.95, 95% confidence interval (CI): 0.66–1.37). The direction of the estimated interactions on the additive scale was consistent with a negative interaction in all three countries (relative excess risk due to interaction (RERI): −0.98, 95% CI: −2.05–0.15, p = 0.09). Conclusion: Our findings indicate competing antagonism, where the two exposures compete to affect the outcome. [ABSTRACT FROM AUTHOR]

Recent studies suggest that the incidence and mortality of amyotrophic lateral sclerosis (ALS) are increasing. Changing environmental factors could influence disease risk differently throughout life span, and also between genders, birth cohorts, and seasons of birth. We aimed at describing long-term ALS mortality trends in Norway between 1951 and 2014 using age-period-cohort analysis. The Norwegian Cause of Death Registry provided ALS mortality data that were age- and sex-adjusted through direct standardization. Poisson regression analyses were used for identification of mortality trends and potential month of birth effects. We identified 5345 ALS cases, of which 54.7 % were men. ALS mortality increased throughout the whole period ( p < 0.001), with a mean annual increase of 1.14 %. The increase was confined to those older than 60 years, but rates consistently dropped amongst the absolute oldest. The increase was mainly driven by birth cohort effects that increased from 1860 until 1934 ( p < 0.001). No month of birth effect or change in sex ratio was found. The continuous increase in ALS mortality since 1951 is best explained by the long-term changes in exposure to risk factors or in case ascertainment, affecting men and women equally in the generations born since 1860 and at least into 1934. [ABSTRACT FROM AUTHOR]

The article presents research which examines if body size influences the risk of multiple sclerosis (MS) in a population-based, case control study in Norway and Italy. It notes the definition of body size-related MS risk by odds ratios (ORs) in logistic regression analyses adjusting for age, smoking and outdoor activity. It reveals the possibility of obesity from childhood until young adulthood to be a risk factor for MS with a seemingly stronger effect in countries mentioned.

The article examines the association between multiple sclerosis (MS) and measures of sun exposure in specific age periods in Norway and Italy. The multinational case-control study (EnvIMS) study included 1660 MS patients and 3050 controls from Italy and Norway. It found converging evidence that underlines the beneficial effect of sun exposure on MS risk.

Epidemiological data suggest that Epstein-Barr virus (EBV) is associated with several autoimmune diseases, such as systemic lupus erythematosus, rheumatoid arthritis and multiple sclerosis. However, it is not clear whether EBV plays a role in the pathogenesis of these diseases, and if so, by which mechanisms the virus may contribute. In this review, we discuss possible viral and immunological mechanisms that might explain associations between EBV and autoimmune diseases and whether these associations represent causes or effects of inflammation and autoimmunity. [ABSTRACT FROM AUTHOR]