The Prevalence of melanocytic nevi among 7-19 years old schoolchildren of Kaunas city in Lithuania: the role of phenotype and sun exposure

Abstract

Introduction & Objectives: The high number of melanocytic nevi (MN) is the most important risk factor for cutaneous malignant melanoma (CMM). MN originate in childhood and are largely influenced by phenotype and sun exposure. However controversial data exists about impact of sun protective measures to the number of MN. The aim of the study was to estimate the Prevalence Of MN And Their Relationships With Phenotype And Sun Exposure Among Schoolchildren. MATERIAL & Methods: A cross-sectional study was conducted on schoolchildren (N=1277) aged 7-19 years from 3 randomly selected schools (a random cluster sample) in Kaunas, Lithuania. The overall response rate of the study was 51.4%. Children underwent a standardized interview concerning sun exposure and sun-protective behavior. Total body MN (all sizes and ≥ 2 mm separately) were counted. Phenotypic features (the color of eyes, hair, skin) and skin phototype (according to the Fitzpatrick’s classification) were assessed. Number of MN was expressed as count per unit of body surface area (MN density). Linear regression analysis was performed on logarithmically transformed MN density (MND). Results: MND of all sizes nevi and nevi ≥ 2 mm increased sequentially with age respectively from median values of 41.13 [IQR 25.18, 54.43] and 4.30 [IQR 2.02, 7.48] at the age of 7-9 years to 47.93 [30.48, 73.75] and 9.44 [IQR 4.89, 17.24] at the age of 16-19 years (p<0.001). Children with light (vs medium, dark) skin color and children with I-II (vs III-IV) skin phototype had a higher MND of all sizes and ≥ 2mm nevi (p<0.001). To the assessment of sun-related behavior, higher density of all sizes MN was found in schoolchildren who tended to spend more time (> 2 hrs vs < 2 hrs per day) at the beach (p=0.031) and who never used (vs used every time) a sunscreen (p=0.016), whereas higher density of MN ≥ 2 mm was associated with beach activities at the midday from 11a.m. till 3p.m (p=0.018). Children who used a sunshade for sun protection at the beach showed significantly lower MND of all sizes and ≥ 2 mm nevi, correspondingly p=0.014 and p=0.027. Conclusions: Number of MN was strongly associated with age, light skin color and I-II skin phototype. Density of all sizes MN was related to long-term lower intensity of sun exposure and higher density of MN ≥ 2 mm - with short-term higher intensity of sun exposure, respectively. Sun protective measures such as a sunscreen, a sunshade and avoidance of long-term beach activities at noon may be effective preventive tools for development of MN in childhood.