The systematic review of previous studies in this area – published in the Journal of Neurology Neurosurgery and Psychiatry – finds that the month a child is born in has a significant effect on subsequent risk of developing MS.
Led by Dr Ruth Dobson from Queen Mary University of London, UK, the study finds that risk of babies developing MS is highest in the month of April, and lowest in October.
“This is likely to be due to ultraviolet light exposure and maternal vitamin D levels, as demonstrated by the relationship between risk and latitude,” write Dobson and her colleagues.
The team cite the significant increase in risk among those born in April and May in addition to a significantly lower risk among those born in October and November, as reason enough to call for supplementation with vitamin D during winter months.
"Through combining existing datasets for month of birth and subsequent MS risk, this study provides the most robust evidence to date that the month of birth effect is a genuine one,” the team states.
“This finding, which supports concepts hypothesised some years previously, surely adds weight to the argument for early intervention studies to prevent MS through vitamin D supplementation.”
The team compared previously published data on almost 152,000 people with MS with expected birth rates for the disease in bid to find out if there was any link between country of birth and risk of developing multiple sclerosis.
At latitudes greater than 52 degrees from the equator, insufficient ultraviolet light of the correct wavelength (290 to 315 nm) reaches the skin between October and March to enable the body to manufacture enough vitamin D during the winter months, say the authors.
The team’s analysis indicated a significant excess risk of 5% among those born in April compared with what would be expected.
Similarly, the risk of MS was 5 to 7% lower among those born between October and November, the data indicated.
Source: Journal of Neurology Neurosurgery and Psychiatry
Published online ahead of print, doi: 10.1136/jnnp-2012-303934
“The month of birth effect in multiple sclerosis: systematic review, meta-analysis and effect of latitude”
Authors: Ruth Dobson, Gavin Giovannoni, Sreeram Ramagopalan