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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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The article focuses on a study which explored the association between major stressful life events and multiple sclerosis (MS) using child death, or a spouse or marital dissolution as indicators of stress. The results of the study showed that bereaved parents experienced no unusual risk of MS compared with parents who did not lose a child, and the study concluded little evidence for a causal association between stressful life events and MS risk.

The article presents a nationwide register-based cohort study which assesses the association between cesarean section (C-section) delivery and the risk of developing multiple sclerosis (MS) in people born from 1973-2005 in Denmark. The registered-based data were analyzed by means of MS incidence rate ratios with 95% confidence intervals obtained in log-linear Poisson regression analyses. The results indicate no significant association between C-section and the risk of developing MS.

In a national cohort comprising 1.5 million Danes born from 1966 to 1992, we studied the association between childhood socioeconomic status (SES) and the risk of multiple sclerosis (MS) from 1981 to 2007 using information about household income and parental educational levels at the person's 15th birthday. The association between childhood SES and MS was evaluated using MS incidence rate ratios with 95% confidence intervals obtained in log-linear Poisson regression analyses. We found no strong association between childhood SES and MS but did observe a tendency toward a reduced risk of MS among children from households with more highly educated parents, particularly mothers. Children whose mothers had a secondary (rate ratio = 0.95, 95% confidence interval: 0.86, 1.04) or higher (rate ratio = 0.86, 95% confidence interval: 0.76, 0.97) education had reduced risks of MS (5% and 14%, respectively) compared with children of mothers with a basic education (P for trend = 0.02). Results were practically unchanged in an analysis restricted to persons aged 15–29 years, among whom the possible effect of own SES on MS risk is considered limited. Overall, SES in childhood seems of no major importance for the subsequent risk of MS; however, offspring of well-educated mothers may be at a slightly reduced risk of MS. [ABSTRACT FROM PUBLISHER]

It has been hypothesized that age at infection with a common microbial agent may be associated with the risk of multiple sclerosis (MS). The authors addressed this hypothesis by using number of older siblings and other sibship characteristics as an approximation of age at exposure to common infections. Data on family characteristics and vital status from the Danish Civil Registration System were used to establish a cohort of all Danes whose mothers had been born in Denmark since 1935. Persons diagnosed with MS during the period 1968–1998 were identified through linkage with the Danish Multiple Sclerosis Register. The cohort of 1.9 million Danes was followed for 28.1 million person-years; during that time, 1,036 persons developed MS. Overall, there was no association between number of older siblings, number of younger siblings, total number of siblings, age distance from the nearest younger sibling, or exposure to younger siblings under 2 years of age and risk of MS later in life. There was no association of MS risk with multiple birth (vs. singleton birth) or with the age of the mother or father at birth. These results do not lend support to the hypothesis that number of older siblings or any of the other sibship characteristics studied is associated with risk of MS. [ABSTRACT FROM AUTHOR]