Melanoma: linked temporal and latitude changes in the United States

The rise in the incidence and mortality from melanoma of the skin is slowing down in younger age groups in the United States. In many White populations, including that of the US, melanoma incidence and mortality rates increase according to proximity of residence to the Equator. Variations with age in this gradient do not seem to have been examined. We examined how the influence of latitude on melanoma rates varied with age. Estimates of age-specific trends by time and by latitude for natural logarithm (Ln) melanoma incidence-rates from the Surveillance, Epidemiology and End Results (SEER) programs, and Ln melanoma mortality rates from the US Vital Statistics were derived from fitted regression equations. Unexpectedly, a decline from old age to youth in the influence of latitude was found for both incidence and mortality from melanoma of the skin in males, and for mortality in females. Further, these changes in the relationship to latitude with age correlated with the changes in time trends with age. The link with exposure suggests that the time trends in melanoma are driven by variations in damage to melanocytes in early life that increases sensitivity to sunlight. This has implications for the general understanding of melanoma etiology and for health education.