A CASE-CONTROL STUDY OF MALIGNANT-MELANOMA OF THE TRUNK AMONG WHITE MALES IN UPSTATE NEW-YORK

To address the increase in the incidence of cutaneous melanoma in upst ate New York in recent decades, a case-control study was conducted of the constitutional and environmental risk factors for malignant melano ma of the trunk among white males. Cases were identified from the New York Cancer Registry from 1977 through 1979 (the period of the greates t relative increase in incidence), and controls were selected using ra ndom digit dialing methods. A total of 324 cases or their next-of-kin and 415 controls were interviewed regarding physical and sociodemograp hic characteristics, lifestyle habits, and medical histories. The foll owing variables were statistically significant in the final logistic r egression analysis: birthmarks (O.R. = 3.87); sunburn easily (O.R. = 1 .83); fair skin tone (O.R. = 1.63); northern European ancestry (O.R. = 1.51); blue eye color (O.R. = 1.46); and participation in water sport s (O.R. = 2.02). Interaction terms between constitutional and environm ental variables resulted in a significant relationship between the pre sence of freckles and bathing two or more times per day. Among freckle d individuals, those who bathed more than once per day had a sixfold e levation in the risk compared to those who bathed less often. In compa rison, the odds ratio for frequent bathing among men without freckles was only 1.24. The data suggest the following hypothesis for further s tudy: the possibility that frequent bathing may be deleterious, especi ally among freckled individuals or those with pigmented nevi.