Lack of Sunlight and Mono Infection Combine to Raise MS Risk
Little exposure to sunlight paired with infection with mononucleosis, a common virus, may put people at risk for multiple sclerosis.
Credit: Ivan Ghezzi

Little exposure to sunlight paired with an infection of the common virus mononucleosis may put people at risk for multiple sclerosis (MS), a new study suggests.

The study, conducted in England, found that the amount of sunlight in a particular area combined with the number of cases of mononucleosis in that region could help explain how MS was distributed across the country.

MS is known to be more common at higher latitudes, where exposure to sunlight is diminished. And previous studies have found exposure to high levels of sunlight is protective against MS. In addition, infection with mononucleosis (commonly referred to as mono), caused by the Epstein-Barr virus, has been linked with MS. But no one had looked at the interaction between these two factors and MS.

The body makes vitamin D when exposed to the ultraviolet B rays (UVB) of sunlight. It’s possible that vitamin D deficiency may lead to an abnormal response to the Epstein-Barr virus, the researchers say, which is in turn is a risk factor for MS.

There is an urgent need for more studies into exactly how these two factors play a role in MS, study researcher George Chaplin, of the department of anthropology at Penn State University, told MyHealthNewsDaily.

In addition, further studies could focus on ways to advance MS prevention. "More research should be done on whether increasing UVB exposure or using vitamin D supplements and possible treatments or vaccines for the Epstein-Barr virus could lead to fewer cases of MS," study researcher Dr. George C. Ebers, of the University of Oxford in the United Kingdom, said in a statement.

MS, sunlight and mono

Multiple sclerosis is a disease that affects the nervous system and has a broad range of symptoms, including diminishing mobility, blurred vision and impaired mental ability, but its course is often unpredictable. It usually strikes people between the ages of 18 and 40.

The researchers looked at hospital admissions in England over seven years. They identified 56,681 cases of MS and 14,621 cases of infectious mononucleosis. They also examined NASA information on the intensity of ultraviolet light in England during this period.

Regions where both low sunlight exposure and infection with mono occurred were correlated with where MS occurred, Chaplin said.

Sunlight exposure and mononucleosis together were able to explain 72 percent of the variance in MS across the country. Sunlight exposure alone accounted for 61 percent of the variance.

Sunlight is still dangerous

The researchers note their study only shows an association and not a direct cause-effect link. The study also did not account for social factors, such as a person's economic status or ethnicity, which may influence the results.

Chaplin emphasizes that the findings are not an endorsement of sunbathing, which may be particularly hazardous for MS patients.

Dangers of sun exposure include "damage to the skin leading to premature aging, skin cancer and dangerous and deadly melanoma," Chaplin said. "For MS sufferers in particular, sunbathing should not be encouraged as there is the danger of overheating — this exacerbates MS and in rare cases has led to immediate death."

The study will be published tomorrow (April 19) in the journal Neurology.

Pass it on: Low exposure to sunlight and infection with mononucleosis may combine to increase the risk of MS.

This story was provided by MyHealthNewsDaily, a sister site to LiveScience.