The association of solar ultraviolet B (UVB) with reducing risk of cancer: multifactorial ecologic analysis of geographic variation in age-adjusted cancer mortality rates.
BACKGROUND
Solar ultraviolet B (UVB) irradiance and vitamin D are associated with reduced cancer mortality rates. However, the previous ecologic study of UVB and cancer mortality rates in the U.S. (Grant, 2002) did not include other risk factors in the analysis.


METHODS
An ecologic study was performed using age-adjusted annual mortality rates for Caucasian Americans for 1950-69 and 1970-94, along with state-averaged values for selected years for alcohol consumption, Hispanic heritage, lung cancer (as a proxy for smoking), poverty, degree of urbanization and UVB in multiple regression analyses.


RESULTS
Models were developed that explained much of the variance in cancer mortality rates, with stronger correlations for the earlier period. Fifteen types of cancer were inversely-associated with UVB. In the earlier period, most of the associations of cancer death rates with alcohol consumption (nine), Hispanic heritage (six), the proxy for smoking (ten), urban residence (seven) and poverty (inverse for eight) agreed well with the literature.


CONCLUSIONS
These results provide additional support for the hypothesis that solar UVB, through photosynthesis of vitamin D, is inversely-associated with cancer mortality rates, and that various other cancer risk-modifying factors do not detract from this link. It is thought that sun avoidance practices after 1980, along with improved cancer treatment, led to reduced associations in the latter period. The results regarding solar UVB should be studied further with additional observational and intervention studies of vitamin D indices and cancer incidence, mortality and survival rates.
Grant
William B
WB
Sunlight, Nutrition and Health Research Center (SUNARC), 2107 Van Ness Avenue, Suite 403B, San Francisco, CA 94109-2529, USA. wgrant@sunarc.org
Garland
Cedric F
CF
D000367:Age Factors; D004463:Ecology; D005260:Female; D006801:Humans; D008297:Male; D015999:Multivariate Analysis; D009369:Neoplasms / Q000401:mortality*; D012307:Risk Factors; D012737:Sex Factors; D012959:Socioeconomic Factors; D013472:Sunlight; D014466:Ultraviolet Rays