[ RadSafe ] Sunlight exposure loweres lymphoma risk

[Marcel Schouwenburg]

Sunlight exposure reduces lymphoma risk
By Angelo DePalma, MedPage Today Staff Writer
Reviewed by Zalman S. Agus, MD; Emeritus Professor at the University of 
Pennsylvania School of Medicine 
<http://www.medpagetoday.com/reviewer.cfm?reviewerid=30>
February 02, 2005
http://www.medpagetoday.com/tbindex1.cfm?tbid=436

For unknown reasons cases of malignant lymphoma have tripled over the 
past 40 years. One hypothesis, which connects sunlight exposure to 
increased risk, has been dispelled by researchers from Sweden's 
Karolinska Institute and Uppsala University. Writing in The Journal of 
the National Cancer Institute, Smedby et al have uncovered a negative, 
statistically significant correlation between exposure to sunlight and 
subsequent development of malignant lymphomas. The study shows that UV 
exposure from the sun and other sources apparently reduces risk, 
particularly for non-Hodgkin's lymphoma, by up to 40%.

The study compared 3,740 patients newly diagnosed with either Hodgkin's 
or non-Hodgkin's lymphoma between 1999 and 2002, with 3,187 randomly 
chosen individuals. Interviews were conducted by telephone. In addition 
to information on lymphoma, participants were asked about other 
diagnosed cancers.

For non-Hodgkin's lymphoma, a "high frequency" of sunbathing (four times 
weekly or more at age 20 or up to 10 years before the interview) was 
associated with a 30% reduction in risk, while those exposed two or more 
times yearly experienced a 40% risk reduction. Results were significant 
to the 0.01 confidence level or better. No significant differences were 
noted among disease subtypes, although associations were stronger for 
B-cell than for T-cell lymphomas. Weaker negative correlations were 
observed for Hodgkin's lymphoma.

The negative correlation held strongly even after adjusting for skin 
type, other types of UV exposure, smoking, education level, occupational 
exposure to pesticides, autoimmune disorders, family history of cancer, 
and history of blood transfusions

Curiously, in this study a history of skin cancer is associated with a 
doubling of risks for both Hodgkin's and non-Hodgkin's lymphoma. The 
authors conclude that this association is probably independent of UV 
exposure.

The authors suggest that if results of their study are duplicated, 
advice to stay out of the sun to prevent melanoma may be unwarranted. 
They caution, however, that more research is needed before changing 
public health policy.

Primary source: Journal of the National Cancer Institute
Source reference:
Journal of the National Cancer Institute, Vol. 97, No. 3, February 2, 2005

Susan Gawarecki <loc at icx.net>