Living in a sunnier climate as a child and young adult may reduce risk of multiple sclerosis

March 7, 2018, American Academy of Neurology

People who live in areas where they are exposed to more of the sun's rays, specifically UV-B rays, may be less likely to develop multiple sclerosis (MS) later in life, according to a study published in the March 7, 2018, online issue of Neurology, the medical journal of the American Academy of Neurology. Exposure in childhood and young adulthood may also reduce risk.

While UV-B rays can cause sunburn and play a role in the development of skin cancer, they also help the body produce vitamin D. Lower levels of vitamin D have been linked to an increased risk of MS.

"While previous studies have shown that more may contribute to a lower risk of MS, our study went further, looking at exposure over a person's life span," said study author Helen Tremlett, Ph.D., of the University of British Columbia in Vancouver, Canada. "We found that where a person lives and the ages at which they are exposed to the sun's UV-B rays may play important roles in reducing the risk of MS."

For the study, researchers identified participants from the larger Nurses' Health Study, including 151 women with MS and 235 women of similar age without MS. Nearly all of the women, 98 percent, were white and 94 percent said they had fair to medium skin. Participants lived across the United States in a variety of climates and locations. Of those with MS, the average age at onset was 40. All of the women had completed questionnaires about summer, winter and lifetime sun exposure.

Researchers divided the women into three groups representing low, moderate and high UV-B ray exposure based on where they lived, specifically looking at latitude, altitude and average cloud cover for each location. In addition, seasonal sun exposure was explored, with high summer sun exposure defined as more than 10 hours per week and more than four hours per week in the winter.

They found that women who lived in sunnier climates with the highest exposure to UV-B rays had 45 percent reduced risk of developing MS across all pre-MS onset age groups when compared to those living in areas with the lowest UV-B ray exposure. When looking at specific age groups, those who lived in areas with the highest levels of UV-B rays between ages 5 to 15 had a 51 percent reduced risk of MS compared to the lowest group. A total of 33 of 147 people with MS, or 22 percent, had high exposure at ages 5 to 15, while 61 people, or 41 percent, had low exposure. In addition, those who spent more time outdoors in the summer at ages 5 to 15 in locations where exposure to UV-B rays was the highest had a 55 percent reduced risk of developing the disease compared to those in the lowest-exposure group.

"Our findings suggest that a higher exposure to the sun's UV-B rays, higher summer outdoor exposure and lower risk of MS can occur not just in childhood, but into early adulthood as well," said Tremlett. "The methods we applied to measure sun exposure could also be used in future studies."

Tremlett continued, "In addition, our research showed that those who did develop MS also had reduced sun or outdoor exposure later in life, in both summer and winter which may have health consequences."

A limitation of the study is that sun exposure was self-reported and memories of how much time was spent in the sun, particularly in youth, may differ from actual exposure time. However, the information related to UV-B was captured using place of residence, which is less likely to be influenced by such factors. Another limitation was that almost all of the study participants were female and white, meaning the results may not apply to other populations.

Explore further: Multiple sclerosis may start later for those who spend teenage summers in the sun

Related Stories

Multiple sclerosis may start later for those who spend teenage summers in the sun

October 7, 2015
A study of people with multiple sclerosis (MS) found that those who spent time in the sun every day during the summer as teens developed the disease later than those reporting not spending time in the sun every day. The study, ...

Are cholesterol-lowering statins associated with reduced Alzheimer risk?

December 12, 2016
An analysis of Medicare data suggests that high use of cholesterol-lowering statins was associated with a reduced risk for Alzheimer disease but that reduction in risk varied by type of statin and race/ethnicity, findings ...

Why do sunbathers live longer than those who avoid the sun?

March 22, 2016
New research looks into the paradox that women who sunbathe are likely to live longer than those who avoid the sun, even though sunbathers are at an increased risk of developing skin cancer.

Outdoor light at night linked with increased breast cancer risk in women

August 17, 2017
Women who live in areas with higher levels of outdoor light at night may be at higher risk for breast cancer than those living in areas with lower levels, according to a large long-term study from Harvard T.H. Chan School ...

Recommended for you

White matter repair and traumatic brain injury

September 20, 2018
Traumatic brain injury (TBI) is a leading cause of death and disability in the U.S., contributing to about 30 percent of all injury deaths, according to the CDC. TBI causes damage to both white and gray matter in the brain, ...

'Gut sense' is hardwired, not hormonal

September 20, 2018
If you've ever felt nauseous before an important presentation, or foggy after a big meal, then you know the power of the gut-brain connection.

Genomic dark matter activity connects Parkinson's and psychiatric diseases

September 20, 2018
Dopamine neurons are located in the midbrain, but their tendril-like axons can branch far into the higher cortical areas, influencing how we move and how we feel. New genetic evidence has revealed that these specialized cells ...

Full, but still feasting: Mouse study reveals how urge to eat overpowers a signal to stop

September 20, 2018
Almost everyone knows the feeling. You're at a restaurant or a holiday meal, and your stomach is telling you it's full, so logically you know you should stop eating.

Gut branches of vagus nerve essential components of brain's reward and motivation system

September 20, 2018
A novel gut-to-brain neural circuit establishes the vagus nerve as an essential component of the brain system that regulates reward and motivation, according to research conducted at the Icahn School of Medicine at Mount ...

Gambling monkeys help scientists find brain area linked to high-risk behavior

September 20, 2018
Monkeys who learned how to gamble have helped researchers pinpoint an area of the brain key to one's willingness to make risky decisions.

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.