Melanoma risk by age and socio-economic status.

To explore the relationship between melanoma incidence, socio-economic status (SES), and site of occurrence, 1,804 cases of melanoma in Washington State from 1974-85 were analyzed by mean income of census tract of residence. (Census tracts are geographic divisions of state counties for which demographic information is provided by state agencies.) For males aged 30-69, as expected, the risk increased with income. Unexpectedly, at age 70 and over the trend was reversed (the heterogeneity of the age relationship was unlikely to be due to chance). In the older men, the increase with low income was found in the cases reported as Hutchinson's melanotic freckle and those which were not, being statistically significant in the latter. These findings suggest a role for long-continued sun exposure in the etiology of malignant melanoma.