Sunlight is associated with decreased multiple sclerosis risk: no interaction with human leukocyte antigen-DRB1*15.

BACKGROUND: Both insufficient exposure to sunlight and vitamin D deficiency have been associated with an increased risk for multiple sclerosis (MS). An interaction between human leukocyte antigen HLA-DRB1*15 and vitamin D in MS was recently proposed. We investigated the association between previous exposure to ultraviolet radiation (UVR), vitamin D status at inclusion in the study, and MS risk including the interaction of these factors with HLA-DRB1*15. METHODS: A population-based case-control study involving 1013 incident cases of MS and 1194 controls was performed in Sweden during 2005-2010. Subjects were classified according to their UVR exposure habits, vitamin D status, and HLA genotypes. The associations between different sun exposure habits/vitamin D levels and MS were calculated as odds ratios (OR) with 95% confidence intervals (CI) using logistic regression. Potential interaction was evaluated by calculating the attributable proportion due to interaction. RESULTS: Subjects with low UVR exposure had a significantly increased risk of MS compared with those who reported the highest exposure (OR 2.2, 95% CI 1.5-3.3). Similarly, subjects who had 25-hydroxy-vitamin D levels less than 50 nM/l had an increased risk for MS (OR 1.4, 95% CI 1.2-1.7). The association between UVR exposure and MS risk persisted after adjustment for vitamin D status. There was no interaction with HLA-DRB1*15 carriage. CONCLUSIONS: UVR and vitamin D seem to affect MS risk in adults independently of HLA-DRB1*15 status. UVR exposure may also exert a protective effect against developing MS via other pathways than those involving vitamin D.

Exposure to environmental tobacco smoke is associated with increased risk for multiple sclerosis.

BACKGROUND: Tobacco smoking has consistently been associated with increased risk for multiple sclerosis. However, data has been inconsistent regarding the influence of passive smoking. OBJECTIVE: The aim was to estimate the influence of passive smoking on the risk for multiple sclerosis. METHODS: A population-based case-control study using incident cases of multiple sclerosis was performed in Sweden, and the study population was restricted to subjects who had never smoked (695 cases, 1635 controls). The incidence of multiple sclerosis among never-smokers who had been exposed to passive smoking was compared with that of never-smokers who had never been exposed by calculating the odds ratio with a 95% confidence interval employing logistic regression. RESULTS: The risk for multiple sclerosis was increased among never-smokers who had been exposed to passive smoking (OR 1.3, 95% CI 1.1-1.6) compared to never-smokers who had never been exposed. The risk increased with increasing duration of exposure (p = 0.003). CONCLUSIONS: Exposure to environmental tobacco smoke is associated with an increased risk for multiple sclerosis. Since smoking, but not usage of oral tobacco in the form of moist snuff, is associated with increased risk for multiple sclerosis, we consider that the critical effects of passive smoking may be the result of irritations in the lungs. Hence, further studies would be valuable in order to clarify whether other forms of lung irritation, such as air pollution, contribute to the triggering of multiple sclerosis.

Epidemiological typing of Streptococcus pneumoniae from various sources in Sweden and India using Box A PCR fingerprinting.

Epidemiological typing of Streptococcus pneumoniae is essential to determine strain relatedness and also to trace resistant clones. The novel Box A PCR assay was used for characterization of S. pneumoniae isolates from two Scandinavian countries and to compare those from India on the Asian continent. In addition, the assay was employed to determine the clonality of 25 pneumococcal strains from an outbreak in a day-care centre in Linköping, Sweden. All 25 showed a unique pattern with 100% homology for 24 of them, thereby establishing the clonal nature of the outbreak. The pneumococcal strains involved in the outbreak belonged to serotype 9 and were resistant to penicillin, with an MIC value of 2 mg/l. Thirty-eight genotypes were obtained when the Box A results were analysed by computer (Molecular Analyst Software with GelCompar). The discriminatory index of the method was D=0.98, which indicates excellent performance. No major segregation of strains from the different geographical locations was observed when a lower level of similarity was used for typing (80%, 13 types). However, at the level chosen for genotyping, 95% (38 genotypes) there was a clear geographical segregation. No correlation between genotype and serotype was seen as strains from a common place of origin were most often of different serotypes. Computer-assisted analysis of the results of Box A PCR typing facilitated the evaluation.