Lower winter sun exposure + vitamin D gene variant = higher MS risk?

As we've said before many times, MS is a "complex" disease, which means a combination of things have to happen or be present in order for someone to develop it. A research team in Australia that has been studying the role of sunlight in the disease has found a pair of different factors that may interact to increase the risk of MS. They analyzed variants in the vitamin D receptor gene in people with MS and controls, while also investigating other topics such as past sun exposure.

While none of the gene variants were overall more common in people with MS than controls, one of them was associated with MS risk in people who reported having had low levels of winter sun exposure as a child. The variant that was more common in the low-exposure MS cases reduces the efficacy of the vitamin D receptor molecule in the body. So perhaps low sun exposure early in life (and therefore low vitamin D production), coupled with less effective use of vitamin D in the body together increase the risk of MS.