| Background. Several lines of evidence have implicated ultraviolet radiation (UVR) as a potential risk factor for non-Hodgkin lymphoma (NHL), including: (1) data demonstrating parallel time trends in melanoma and NHL incidence rates; (2) elevated melanoma risk among NHL patients; and (3) immune suppression following UVR exposure. However, recent studies that have examined the association between individual sun exposure and lymphoma risk have found an inverse relationship, suggesting that increased sun exposure is protective against lymphoma. As sunlight is our major source of Vitamin D, one proposed explanation for this unexpected finding is that the measures of sun exposure in two studies are actually proxy measurements of Vitamin D status, and that Vitamin D is protective against lymphoma. Animal and human studies have investigated the association between Vitamin D and other cancers, and provide support for a protective effect of Vitamin D related to malignancy. The purpose of this case-control study is to test the hypothesis that past vitamin D insufficiency, as predicted by sun sensitivity and average past sun exposure, is a risk factor for lymphoma.;Methods. Between October 2005 and September 2007, 140 cases and 139 controls were recruited from the James P. Wilmot Cancer Center Lymphoma Clinic and General Neurology Clinic, respectively, both outpatient clinics at the University of Rochester Medical Center, Rochester, New York. A serum sample and self-administered survey were collected from each subject. Serum vitamin D (25(OH)D) was quantified by radioimmunoassay (RIA; Heartland Assays Inc., Ames, IA). A predictive linear regression model for measured 25(OH)D was developed based on sun sensitivity, recent sun exposure (within the past month), and other vitamin D predictor variables, as assessed by the survey. The predictive model was used to estimate each subject's average 25(OH)D level 5-10 years ago. These estimated 25(OH)D levels were used to examine the association between past vitamin D insufficiency (25(OH)D < 30 ng/mL) and lymphoma risk.;Results. Our predictive linear regression model accounted for 42% of the variability observed in vitamin D, and identified the following independent predictors of 25(OH)D: sun exposure, sunbathing, tanning bed use, daily multivitamin use, milk intake, fatty fish intake, BMI, race, age. Tanning bed use has the largest impact on 25(OH)D (average increase of 15.07 ng/mL with tanning bed use), followed by sunbathing with the intention to tan (average increase of 9.71 for >1 time/wk). Past (5-10 years ago) vitamin D insufficiency (25(OH)D < 30 ng/mL) was detected in 66% of the study population. After multivariate adjustment for age, gender, race, prior skin cancer diagnosis, known family history of lymphoma, known family history of other cancer, and BMI, the odds ratio estimate of the association between past vitamin D insufficiency and lymphoma risk was 0.68 (0.38--1.23), p=0.1992.;Conclusions. This study fails to provide evidence to suggest an association between estimated past vitamin D insufficiency and lymphoma risk. |
