Abstract
The study examined results from previous studies of early life vitamin D exposure and risk of MS in adulthood, including studies on season or month of birth and of migration. A systematic review was conducted using PubMed and Web of Science databases as well as checking references cited in articles. The quality of studies was assessed using the Newcastle-Ottawa scale and the AMSTAR score. Twenty-eight studies were selected for analysis. Of these, six population studies investigated early life vitamin D exposure and risk of MS, and three found inverse while the remaining found no associations. A consistent seasonal tendency for MS seemed evident from 11/15 studies, finding a reduced occurrence of MS for Northern hemisphere children who were born late autumn, and late fall for children born in the Southern hemisphere. This was also confirmed by pooled analysis of 6/15 studies. Results of the migration studies showed an increased risk of MS if migration from high to low-MS-risk areas had occurred after age 15 years, while risk of MS was reduced for those migrating earlier in life (<15years). A similar, but inverse risk pattern was observed among migrants from low to high-MS-risk areas. One study found an increased risk of MS in the second generation of migrants when migrating from low to high-MS-risk areas. An association between early life vitamin D and later risk of MS seems possible, however evidence is still insufficient to conclude that low vitamin D exposure in early life increases the risk of MS in adulthood.PROSPERO register number: CRD 42016043229.
Highlights
Multiple sclerosis (MS) is a chronic autoimmune demyelinating disease that affects the Central Nervous System (CNS)
Vital to search for aetiological factors for MS and to identify cost-effective preventive strategies to reduce the burden of disease
The analysis revealed 6% fewer than expected MS cases in March (SIR 0.94, 95%CI, 0.89–1.0) and 12% more MS births than expected in April (SIR 1.12, 95%CI, 1.06–1.18) with moderate heterogeneity in May, June, July and high heterogeneity in November and December (for further details of meta-analysis results by months (S1 Fig))
Summary
Multiple sclerosis (MS) is a chronic autoimmune demyelinating disease that affects the Central Nervous System (CNS). It is one of the most common neurological disorders occurring in young and middle-aged adults and is more common in women than men [1,2]. The disease decreases the quality of patients’s life and causes a considerable health and economic burden to society [3]. It is, vital to search for aetiological factors for MS and to identify cost-effective preventive strategies to reduce the burden of disease
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