Constitutional factors and sun exposure in relation to nevi: a population-based cross-sectional study.

A survey of benign melanocytic nevi (moles), suspected precursors or markers for melanoma, was conducted in Washington State among 717 randomly selected 18- to 50-year-old white adults who participated in a telephone interview in 1990-1991. Participants were questioned about constitutional factors, time spent in the sun, and severe sunburns over three time periods and were asked to count the raised nevi on both their arms. Logistic regression was used to examine the risk for 2+ nevi compared with none. An odds ratio (OR) of 2.0 (95% confidence interval (CI) 1.3-3.1) was seen for current freckling. Skin color, tendency to burn, and inability to tan were important risk factors but were not independent of each other. Individuals with a history of severe sunburns had an increased risk of nevi: OR = 1.9 (95% CI 0.9-3.9) for 3+ severe sunburns compared with none in the last 5 years; OR = 2.0 (95% CI 1.2-3.1) for 4+ severe teenage sunburns; and OR = 3.1 (95% CI 1.7-5.3) for 4+ severe childhood sunburns. Furthermore, childhood sunburns were related to nevi independently of sun sensitivity and teenage and recent sunburns: OR = 2.0 (95% CI 1.0-4.0) for 4+ severe sunburns. These data suggest that childhood sunburns are important in the etiology of nevi. This study supports prior studies of the relation between melanoma and early sun exposure.