Factors associated with atypical moles in New Hampshire, USA.

Only a few studies, conducted in Sweden, assessed factors associated with the presence of atypical moles in the general population. We conducted a population-based, case-control study in New Hampshire, USA, to identify factors associated with atypical moles. In our study, atypical moles affected 14% of the study population. The adjusted odds ratio (OR) was 0.34 (95% confidence interval (CI) = 0.14-0.80) for those with the highest adulthood recreational sun exposure, relative to the lowest. The OR for any freckles, compared to none, was 2.24 (95% CI = 1.18-4.25). We found a linear relationship between the number of benign moles and the presence of atypical moles (p for trend = 0.0001). The OR was 7.34 (95% CI = 3.03-17.80) for > 15 benign moles, relative to 0-4. Our data indicate that freckles and benign moles, which may reflect melanocytic inducibility, are strongly associated with atypical moles. The inverse association with sun exposure should be considered with caution.