The role of phenotype, body mass index, parental and sun exposure factors in the prevalence of melanocytic nevi among schoolchildren in Lithuania.

Abstract

The occurrence and number of melanocytic nevi (MN) are among the most important known risk factors for the development of cutaneous melanoma (CM). To estimate the prevalence of MN among schoolchildren and its relationship with phenotype, body mass index (BMI), parental and sun exposure factors. A cross-sectional study was conducted on N = 1277 schoolchildren aged 7-19 years old in Kaunas city, Lithuania. Subjects were interviewed using a self-administered questionnaire and were assessed by a dermatologist. MN of all sizes and ≥2 mm in diameter were counted; phenotypic features and skin phototype were defined. BMI and body surface area (BSA) were calculated. Whole-body MN counts were expressed both as totals and as counts per unit of BSA - MN density (MND). Biological parents completed questionnaires regarding nevus counts, family history of skin cancer and CM. The numbers of all sizes and ≥2 mm MN increased according to age, respectively, from median values of 44 (IQR 28, 60) and 5 (IQR 2, 8) at the age of 7-9 years to 85 (IQR 55, 128) and 16 (IQR 8, 30) at the age of 16-19 years. A higher MND was found in children with light skin colour (P < 0.001), I-II skin phototype (P < 0.001), extensive facial freckling (P < 0.005) and multiple nevi on the father's and mother's arms (P < 0.05). 20.2% of pupils were overweight or obese, 130 males and 118 females. Overweight and obese children had a higher all sizes MND (P = 0.033, P = 0.044). Acquired suntan at the end of summer was associated with a higher all sizes MND (P < 0.05), outdoor activities at midday - with a higher ≥2 mm MND (P = 0.047) respectively. The prevalence of MN among schoolchildren is age-dependent and strongly determined by skin colour, skin phototype, facial freckling and BMI. Parental nevus numbers, acquired suntan and outdoor activities at midday must be considered.