Influence of cumulative sun exposure on the prevalence of common acquired nevi

Background: Conflicting evidence exists on the relation between sun exposure and the number of common acquired nevi. The increase in the number of common acquired nevi until early adulthood and their greater concentration on sun-exposed areas suggested that the growth of common acquired nevi is promoted by UV radiation. Nevertheless, it was noticed that although solar exposure accumulates with age, the number of common acquired nevi decreases after the third decade. Objective: Our purpose was to examine the relation between the prevalence of common acquired nevi and accumulative sun exposure. Methods: The number of common acquired nevi on 128 patients with multiple solar keratoses (SK) was compared with their number on 82 control subjects. The existence of SK served as a biologic marker for long-term solar effects. Results: On patients with SK we counted 1285 nevi (mean 10.0 nevi per person) and on control subjects, 1521 nevi (mean 18.5 nevi) (p = 0.0046; Kruskal-Wallis test). The finding that persons exhibiting signs of accumulating sun effects have fewer nevi was maintained irrespective to differences of gender, occupation, and complexion. Conclusion: Our data suggest that accumulating solar effects may contribute to the natural maturation and elimination of common acquired nevi in late adulthood.