UV, latitude, and spatial trends in prostate cancer mortality: all sunlight is not the same (United States).

OBJECTIVE: We showed previously that Caucasian mortality rates from prostate cancer for 1970-1979 are significantly inversely correlated with ultraviolet (UV) radiation. We now present the analysis of prostate cancer mortality data over a 45-year period (1950-1994) in order to examine the persistence of this pattern. Furthermore, because vitamin D synthesis does not occur during winter months at latitudes higher than 40 degrees N, we examined this relationship above and below 40 degrees N latitude.
METHODS: We used trend surface and linear regression analyses to characterize the relationship between prostate cancer mortality and UV radiation for U.S. counties at northern and southern latitudes.
RESULTS: For U.S. Caucasians, prostate cancer mortality rates at the county and SEA levels followed a significant north-south spatial trend that is the inverse of UV radiation. We found significant inverse correlations between UV radiation and prostate cancer mortality at all time points over this 45-year period. These correlations were significantly more pronounced at locations north of 40 degrees N latitude.
CONCLUSIONS: Our analyses confirm and extend our findings that the geographic distribution of prostate cancer mortality is the inverse of that of UV radiation. This effect is strongest in counties north of 40 degrees N latitude, where vitamin D synthesis is limited to non-winter months. These findings add additional support for the hypothesis that vitamin D insufficiency increases risk for prostate cancer.