The research on sun exposure and MS prevention is now so established that it is irrefutable. This study adds further to the body of evidence.
Researchers from Norway and Italy undertook a classic case control study, that is comparing people with an illness to control people without the illness, and looking at particular risk factors and how much more or less common they were in the group with the illness.
In this case, people with and without MS filled in questionnaires about sun exposure while growing up. They then compared the amount of sun exposure, measured in four categories, in those with MS to those without.
Those with the least sun exposure in Norway had an 82% higher risk of developing MS compared with those with the most sun exposure, and 49% greater risk in Italy. Interestingly, it was also found that in Norway, frequent sunscreen use up to the age of six years old led to a 44% greater risk of developing MS.
It seems likely that the greater risk modification from frequent sun exposure was seen in Norway because in summer, it was much more common for people to get frequent sun, and there was a much bigger difference between summer and winter in amount of sun exposure.
The greatest effect of infrequent sun exposure was seen in early childhood in Italy and in late adolescence in Norway. The paper strongly reinforces the evidence showing that adequate sun exposure in those at high risk of MS, that is close relatives of people with MS, is important in reducing that risk.
For people with MS, there is every reason to encourage children and siblings to get adequate sun exposure, as per the guidelines suggested by OMS.