Exposure to passive smoking during adolescence is associated with an increased risk of developing multiple sclerosis.

BACKGROUND: Environmental factors are associated with acquiring multiple sclerosis (MS) particularly in adolescence. OBJECTIVE: To test for association between MS and exposure to passive smoking at the age of 10-19. METHODS: A total of 919 patients from the Danish MS Registry and Biobank and 3419 healthy blood donors who had not smoked before the age of 19 were targeted. We analyzed separately for each sex and for those never-smokers (cohort 1) and active smokers above the age of 19 (cohort 2). All participants completed standardized questionnaires about smoking and lifestyle. We matched cases and controls in the ratio of 1:2 by propensity scores discarding unmatchable individuals and used logistic regression adjusted for all covariates and interactions. RESULTS: After matching, we included 110/213 male cases/controls and 232/377 female case/controls in cohort 1. In cohort 2, the numbers were 160/320 and 417/760, respectively. Among women in cohort 1, the odds ratio (OR) for MS by passive smoking at the age of 10-19 was 1.432 (p = 0.037) but in men it was 1.232 (p = 0.39). Among men in cohort 2, OR was 1.593 (p = 0.022) but among women it was only 1.102 (p = 0.44). CONCLUSION: Among never smokers, female MS cases were more often than female controls reported with passive smoking between the age of 10 and 19, and among smokers above the age of 19, male MS patients were more often than male controls reported with passive smoking.

Alcohol consumption in adolescence is associated with a lower risk of multiple sclerosis in a Danish cohort.

BACKGROUND AND OBJECTIVE: Due to the possible existence of a vulnerable period of multiple sclerosis (MS) susceptibility in adolescence and because Danish teenagers have a high alcohol consumption, we investigated the association between alcohol consumption at ages 15-19 and the risk of developing MS. METHODS: A total of 1717 patients with MS and 4685 healthy blood donors filled in a comprehensive environmental and lifestyle questionnaire. Data were analysed by logistic regression models and adjusted for selected confounders. RESULTS: We found an inverse association between alcohol consumption in adolescence and risk of developing MS in both women (p < 0.001) and men (p = 0.012). Women with low alcohol consumption had an odds ratio (OR) of 0.56 (95% confidence interval (CI): 0.47-0.66) compared with non-drinking women. The ORs were similar for women with moderate (OR = 0.49, 95% CI: 0.38-0.62) and high consumption (OR = 0.57, 95% CI: 0.38-0.84). Men with low alcohol consumption had an OR of 0.69 (95% CI: 0.53-0.89) compared with non-drinking men but no decreased risk was found for men with moderate and high consumption. CONCLUSION: Alcohol consumption in adolescence was associated with lower risk of developing MS among both sexes.

Smoking is associated with increased disease activity during natalizumab treatment in multiple sclerosis.

BACKGROUND: Smoking has been associated with increased multiple sclerosis (MS) risk, disease worsening, and progression in MS patients. Furthermore, interactions between smoking and human leukocyte antigen (HLA) genes have been shown for MS risk. Recently, we found that smoking was associated with an increased relapse rate in interferon-beta-treated relapsing-remitting multiple sclerosis (RRMS) patients. OBJECTIVES: We examined the association between smoking and relapses in natalizumab-treated RRMS patients. Second, we investigated if an interaction between smoking and HLA-DRB1*15:01 or HLA-A*02:01 affected the number of relapses during treatment. METHODS: In this observational cohort study, 355 natalizumab-treated RRMS patients were assessed. Prespecified criteria excluded 62 patients. Clinical data from the starting of treatment to the two-year follow-up visit were collected. Smoking status was obtained by a questionnaire survey. TaqMan allelic discrimination was used for genotyping of tag single-nucleotide polymorphisms (SNPs) for HLA-DRB1*15:01 and HLA-A*02:01. Negative binomial regression analysis was used to analyze the association between relapse rate and smoking intensity and HLA. RESULTS: One pack of cigarettes (20 cigarettes) per day during natalizumab treatment increased the relapse rate during treatment with 38% (incidence rate ratio (IRR) = 1.38, 95% confidence interval (CI): 1.08-1.77, p = 0.01). No association or interaction was found between smoking and HLA-DRB1*15:01 or HLA-A*02:01, respectively. CONCLUSION: Smoking intensity was significantly associated with the number of relapses during natalizumab treatment.