Sunshine May Lower Multiple Sclerosis Risk

Jan. 14, 2004 -- Living in a sunny place may lower a person's risk of developing multiple sclerosis.

A new study shows that prolonged exposure to low levels of solar radiation may have a protective effect against the disease.

The exact cause of multiple sclerosis is unknown, but previous research has shown that the immune disorder is more common in areas farther away from the equator -- areas with fewer hours of sunlight. For example, multiple sclerosis is more common in Canada and the northern states of the U.S. than in the southern states.

For that reason, researchers have speculated that sunshine might protect against the disease, but there has been little scientific evidence to back up that theory.

But in this study, researchers used the frequency of skin cancer as a marker for sun exposure and found skin cancer was indeed less common among people with MS.

Sunshine May Protect Against Multiple Sclerosis

The study, published in the January issue of the Journal of Epidemiology and Community Health, compared cancer rates among more than 5,000 people with multiple sclerosis and 430,000 English people with other nerve or autoimmune conditions.

Researchers found that the prevalence of skin cancers in people with MS was significantly lower than in the comparison group. This difference was greatest among skin cancers other than melanoma.

Most skin cancers are closely associated with prolonged, continuous exposure to sunshine, but melanoma is the type of skin cancer most likely to be the result of brief but intense periods of exposure to very hot sun.

Researchers say previous studies show that a minimum of sunlight exposure throughout the year may help protect against multiple sclerosis.

They suggest that sunshine may interfere with the development of multiple sclerosis by affecting the immune system response, possibly through the production of vitamin D and melatonin (substances produced in the body in response to sun exposure).