Sun Exposure May Help Prevent Non-Hodgkin’s Lymphoma

Pooled data from 10 studies suggests that recreational sun exposure may help prevent non-Hodgkin's lymphoma (NHL)—a type of blood cancer involving the lymph nodes.

“These results could be taken to suggest that, if sun exposure does protect against NHL, it is an intermittent pattern of sun exposure that is the most protective,” Anne Kricker of the University of Sydney in New South Wales, Australia and colleagues note in the International Journal of Cancer.

They add that sun exposure could exert its anti-cancer effects by boosting vitamin D production in the skin.

Controversially, some investigators have proposed that sun exposure increases the risk of NHL, given that people with skin cancer have a higher risk of the disease and that rates of melanoma have risen in tandem with NHL.

However, four studies conducted between 2004 and 2007 that directly investigated the relationship found sun exposure appeared to protect against NHL; a fifth study, in women only, showed an increased likelihood of NHL with sun exposure.

To systematically evaluate NHL risk and sun exposure, Kricker and colleagues looked at these five studies and an additional five from an international lymphoma study group. The studies included a total of 8,243 people with NHL and 9,697 people without the disease.

They found that recreational sun exposure—defined as the number of hours spent in the sun on non-working days—between the ages of 18 and 40, as well as in the 10 years prior to NHL diagnosis, reduced the risk of the disease.

There was no association between work-related sun exposure and NHL risk. Total sun exposure was linked to reduced risk, but the relationship wasn't statistically significant.

The researchers do note that other factors could account for the relationship—such as exercise, given that people with more recreational sun exposure likely would be more physically active—and say that studies comparing the amount of vitamin D people have in their blood and their NHL risk will provide a more certain answer.