Most of us are familiar with the evidence to support the theory that that low vitamin D levels are related to the risk of multiple sclerosis. Researchers are also studying the ways in which exposure to vitamin D after diagnosis may impact the progression of MS. (Of course, there are many people that have believed this for years and take supplements to make sure their vitamin D level is within a certain non-deficient range.)
Usually, the research has focused on vitamin D supplementation or levels of vitamin D in the blood. However, a recent study looked at sunlight exposure and disability progression in people with relapsing-remitting MS (RRMS) as well as primary progressive MS (PPMS).
The study was conducted among 1372 people registered with the Flemish MS Society in Belgium who answered a survey. The researchers looked at amount of sun exposure and skin type and how these related to MS-related disability, which was defined as 6.0 on the Expanded Disability Status Scale (a score of 6.0 indicates that the person needs some assistance to walk).
Here is what the research showed:
People with RRMS who "always" wore sunscreen were 1.8 times more likely to have reached an EDSS of 6.0 or higher than those who "never" or "sometimes" wore it.
People with RRMS who reported equal or higher levels of sun exposure than their peers without MS were about 30% less likely to have reached an EDSS score of 6.0.
Interestingly, people with PPMS who reported having "sun sensitivity" from birth, defined as burning within 30 minutes of being in the sun, were 1.8 times more likely to have reached an EDSS score of at least 6.0 than those with less sensitive skin. This was not the case in people with RRMS.
Researchers are not sure what these results mean. It could be that sun exposure has a beneficial effect on people with MS, perhaps because of increasing their vitamin D levels. It could also be a situation of "reverse causality," meaning that people who are less mobile will naturally spend less time in the sun because their outdoor activity is more limited.
We have to be careful not to draw too many conclusions from this study, as there are several weaknesses to the research. Only 50% of people contacted responded to the survey. The survey was based on self-reporting, which can lead to recall bias – in other words, a person’s awareness of the possible link between vitamin D and MS might have influenced her or his answers. For example, this knowledge might have influenced them to say they didn't get as much sun as people without MS did. So while this is an interesting study to generate hypotheses for future research, this is NOT a call to stop wearing sunscreen and hang out in the sun all day.
Remember, although I do think sunlight makes me feel better, we are all still susceptible to sun damage and skin cancer. I still put sunscreen on before stepping outside. I also limit my time in the sun. Like most people with MS, I am also heat intolerant, so when the temperature gets above 85 degrees or so, I can be found inside.
Source: MB D’hooghe, P Haentjens, G Nagels, M Garmyn, and J De Keyser
Sunlight exposure and sun sensitivity associated with disability progression in multiple sclerosis. Multiple Sclerosis. April 2012 18: 451-459,