Environmental risk factors for multiple sclerosis. Part II: Noninfectious factors: Environmental Risk Factors for MS

There is no author summary for this article yet. Authors can add summaries to their articles on ScienceOpen to make them more accessible to a non-specialist audience.

Abstract

As discussed in Part I of this review, the geographic distribution of multiple sclerosis (MS) and the change in risk among migrants provide compelling evidence for the existence of strong environmental determinants of MS, where "environmental" is broadly defined to include differences in diet and other behaviors. As we did for infections, we focus here primarily on those factors that may contribute to explain the geographic variations in MS prevalence and the change in risk among migrants. Among these, sunlight exposure emerges as being the most likely candidate. Because the effects of sun exposure may be mediated by vitamin D, we also examine the evidence linking vitamin D intake or status to MS risk. Furthermore, we review the evidence on cigarette smoking, which cannot explain the geographic variations in MS risk, but may contribute to the recently reported increases in the female/male ratio in MS incidence. Other proposed risk factors for MS are mentioned only briefly; although we recognize that some of these might be genuine, evidence is usually sparse and unpersuasive.

Related collections

Most cited references 3

Record: found
Abstract: found
Article: not found

Sex ratio of multiple sclerosis in Canada: a longitudinal study.

Sarah-Michelle Orton, Blanca Herrera, Irene Yee … (2006)

Incidence of multiple sclerosis is thought to be increasing, but this notion has been difficult to substantiate. In a longitudinal population-based dataset of patients with multiple sclerosis obtained over more than three decades, we did not show a difference in time to diagnosis by sex. We reasoned that if a sex-specific change in incidence was occurring, the female to male sex ratio would serve as a surrogate of incidence change. Since environmental risk factors seem to act early in life, we calculated sex ratios by birth year in 27 074 Canadian patients with multiple sclerosis identified as part of a longitudinal population-based dataset. The female to male sex ratio by year of birth has been increasing for at least 50 years and now exceeds 3.2:1 in Canada. Year of birth was a significant predictor for sex ratio (p<0.0001, chi(2)=124.4; rank correlation r=0.84). The substantial increase in the female to male sex ratio in Canada seems to result from a disproportional increase in incidence of multiple sclerosis in women. This rapid change must have environmental origins even if it is associated with a gene-environment interaction, and implies that a large proportion of multiple sclerosis cases may be preventable in situ. Although the reasons why incidence of the disease is increasing are unknown, there are major implications for health-care provision because lifetime costs of multiple sclerosis exceed pound1 million per case in the UK.

0 comments Cited 197 times – based on 0 reviews      Review now

Bookmark

Record: found
Abstract: found
Article: not found

Epidemiology of multiple sclerosis in US veterans: III. Migration and the risk of MS.

J. Kurtzke, J. Norman, Hugh Beebe (1985)

World War II or Korean Conflict veterans with MS (5,305 in number) and pre-illness-matched controls were compared for residence at birth and entry on active duty (EAD) within three north-south tiers of states in the United States. A strong north-south gradient of MS risk was present. Migrants were defined as those whose birth and EAD tier differed. For white men of World War II, all white men, and all whites, there were highly significant reductions in risk for moves southward from either the north or middle tier, and increases in risk for moves northward from the middle tier. Increases similar in magnitude of middle to north did not attain statistical significance in the few southern-born migrants. For the small groups of black men and white men of Korean service, trends were similar but did not attain significance, whereas for white women, they were of borderline significance. Findings imply an environmental cause for MS, with acquisition years before symptom-onset.