INCREASE OF MELANOCYTIC NEVUS COUNTS IN CHILDREN DURING 5 YEARS OF FOLLOW-UP AND ANALYSIS OF ASSOCIATED FACTORS

Objectives: To investigate nevus development in childhood and to exami ne causative related factors such as pigment phenotype and the role of sun exposure in the development of melanocytic nevi. Design and Parti cipants: Nevus counts were performed in kindergarteners (n=866) before the age of 7 years and again 5 years later (n=377). Eligible for anal ysis were 357 children who were examined twice. Possible related facto rs were searched for by standardized interviews with parents. Results: The mean number of nevi measuring 1 mm or more was 9 in the first exa mination and the number measuring 2 mm or more, 4. Five years later, t he mean number of nevi measuring 1 mm or more was 40 and the number me asuring 2 mm or more was it. Children with poor sun tolerance had stat istically significant more nevi (relative risk, 3.7; 95% confidence in terval, 1.9-7.2). The presence of freckles was a strong predictor for a high increase of melanocytic nevi (relative risk, 2.1; 95% confidenc e interval, 1.3-3.3). The number of days per year with intensive solar exposure was an independent prognostic factor. The relative risk for the development of melanocytic nevi was increased by a factor of 1.6 i n children who had more than 21 days of intensive sun exposure per yea r (95% confidence interval, 1.0-2.5). Conclusion: The development of m elanocytic nevi in childhood is strongly related to characteristics of pigmentation associated with poor sun tolerance. In addition, we foun d evidence for the influence of UV radiation on the number of acquired melanocytic nevi in childhood.