How Living In Sunny Places Can Help Reduce Risks Of Multiple Sclerosis

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Some people believe it is best to live somewhere that experiences a range of seasons, from warm to cold temperatures, with a mixture of sun, rain, and snow. However, it is obvious that sunny and warm weather is preferable from a health standpoint.

Sunny weather is not only ideal for going outside and enjoying the sun, but it also tends to make people happier and more upbeat than wet or gloomy conditions. Going outside and moving around in a way that is only possible in sunny weather causes a kind of internal feedback loop. And engaging in that kind of exercise can help you not only stay in shape but also feel better overall by relieving stress, maintaining the health of your joints, and even cleansing your nasal passages by inhaling fresh air.

In addition to the wide array of health benefits that living in places with sunny weather, living in areas with more exposure to the sun’s rays, particularly UV-B rays, may reduce the risk of developing multiple sclerosis (MS) later in life, according to a study published in the medical journal of the American Academy of Neurology. 

The Link Between Sun Exposure Over Life Course and Multiple Sclerosis

In the chronic condition known as multiple sclerosis (MS), the central nervous system (CNS) targets the body’s immune response.

There is no known cause of MS. Low historical sunshine exposure, or lower latitudes have been linked in previous studies to higher MS risk. Evidence links low vitamin D levels to an increased risk of MS. But exposure to sunshine might have its effects, perhaps via different immunomodulatory pathways. Measuring previous sun exposure is extremely difficult, which makes it difficult to investigate sunlight’s potential impact on MS.

In addition, whereas much research identifies early infancy and adolescence as vulnerable times, the majority do not evaluate environmental exposures far beyond these times. However, timing is crucial when designing workable, efficient intervention trials to reduce the incidence of MS. Furthermore, although vitamin D insufficiency is prevalent and quantifiable in MS patients, it is unclear whether it is linked to decreased sun exposure once the disease occurs.

Therefore, the American Academy of Neurology researchers investigated the timing of exposure by season (summer, winter), age, and the relationship between prior solar exposure and MS risk using objective and self-reported measures. Additionally, they discussed sun-related customs and how they can alter as MS patients age.

One hundred fifty-one women with MS and 235 women of a similar age without MS were selected for the study from the larger Nurses’ Health Study; nearly all of the women, 98 percent, were white, and 94 percent reported having fair to medium skin. Participants resided in different regions and climates all over the United States. The average age of onset for those with MS was 40. The questionnaires about summer, winter, and lifetime sun exposure had all been completed by the participants.

Researchers looked at each site’s latitude, altitude, and average cloud cover to split the women into three groups that indicate low, moderate, and high UV-B exposure. Additionally, the effects of seasonal sun exposure were investigated, with high summer sun exposure being defined as more than 10 hours per week and high winter sun exposure as more than 4 hours per week.

According to the research, the location of a person’s home and the age at which they are exposed to UV-B rays from the sun may be key factors in lowering their chance of developing MS. Furthermore:

  • Compared to women who lived in places with the least UV-B ray exposure, those who lived in sunnier climes with the strongest UV-B ray exposure had a 45 percent lower risk of having MS across all pre-MS onset age groups.
  • Between the ages of 5 and 15, people who resided in areas with the highest concentrations of UV-B rays had a 51 percent lower risk of developing MS than those who did not.
  • Out of 147 MS patients, 33 (or 22%) had high exposure between the ages of 5 and 15, while 61 (or 41%) had low exposure.
  • Ages 5 to 15 summertime outdoor time in areas with the highest UV-B exposure was associated with a 55 percent lower chance of acquiring the disease compared to the lowest-exposure group.

The study’s findings indicate that more UV-B exposure, more outdoor time during the summer, and a lower risk of MS can occur in childhood and early adulthood. The research also shows that those who did get MS also had less outdoor or sun exposure later in life, in both the summer and the winter, which could have negative health effects.

The researchers also identified several caveats indicating that self-reported sun exposure was involved and that memory of how much time was spent in the sun, particularly when young, may not match real exposure time. However, the data on UV-B exposure was obtained from a location of residence, which is less likely to be affected by such circumstances. Another drawback was that almost all the study participants were female and white. Thus the findings might not be generalizable to other populations.

Journal Reference

Tremlett, H., Zhu, F., Ascherio, A., & Munger, K. L. (2018). SUN exposure over the life course and associations with multiple sclerosis. Neurology, 90(14). https://doi.org/10.1212/wnl.0000000000005257 

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