SUNLIGHT, VITAMIN-D, AND OVARIAN-CANCER MORTALITY-RATES IN US WOMEN

Background. In general, ovarian cancer incidence and mortality is high er in northern than southern latitudes. This ecologic study tests the hypothesis that vitamin D produced in the skin from sunlight exposure may be associated with a protective action in ovarian cancer mortality . Methods. The association between average annual sunlight energy and age-specific ovarian cancer mortality rates in counties containing the 100 largest US cities was evaluated for 1979-1988. Simple linear regr ession was performed by decade using sunlight and ozone as independent variables and ovarian cancer rates as the dependent variable. Multipl e regression was used to adjust for ozone and sulphur dioxide, since t hese atmospheric components may absorb ultraviolet light. Results. Fat al ovarian cancer in these areas was inversely proportional to mean an nual intensity of local sunlight in a univariate analysis (P = 0.0001) , and in a regression adjusted for air pollution (P = 0.04). The assoc iation was also seen when restricted to 27 major urban areas of the US ; however, probably due to a small sample size, this statistic did not reach significance. Conclusions. This ecologic study supports the hyp othesis that sunlight may be a protective factor for ovarian cancer mo rtality.