Role of ultraviolet B irradiance and vitamin D in prevention of ovarian cancer

BACKGROUND: There is a north-south gradient in age-adjusted mortality rates of ovarian cancer in the United States, with the highest rates in the Northeast and the lowest in the South through Southwest. This suggests that lower levels of solar irradiance might be associated with higher risk of ovarian cancer. Laboratory findings also suggest that low levels of vitamin D metabolites could play a role in the etiology of ovarian cancer. METHODS: The association of solar ultraviolet B (UVB) irradiance, stratospheric column ozone, and fertility rates at ages 15 to 19 years with incidence rates of ovarian cancer in 175 countries in 2002 were examined using multiple linear regression in 2006. RESULTS: Age-adjusted ovarian cancer incidence rates generally were highest in countries located at higher latitudes (R(2)=0.45, p< or =0.01). According to multivariate analysis, UVB irradiance (p< or =0.002) and fertility rates at ages 15 to 19 (p=0.01) were inversely associated with incidence rates, while stratospheric ozone (p< or =0.0008), which reduces transmission of UVB, was positively associated with incidence (R(2)=0.49, p<0.0001). CONCLUSIONS: Solar UVB irradiance was inversely associated with incidence rates of ovarian cancer in this study, adding new evidence to the theory that vitamin D might play a role in the prevention of ovarian cancer. Cohort studies are needed to confirm this possible association.