Nevus counts on body sites that are intermittently exposed to the sun are higher among non-Hispanic white girls than among non-Hispanic white boys between ages 3 and 16 years, and are also higher among white Hispanic girls compared with white Hispanic boys between ages 11 and 16 years, according to the results of a longitudinal, observational cohort study from the Colorado Kids Skin Care Program. Findings from the analysis were published in JAMA Dermatology.1

The investigators sought to describe nevus acquisition from age 3 to 16 years in white youths, and to assess variations based on sex, Hispanic ethnicity, and body sites that are chronically vs intermittently exposed to the sun. The study was performed between June 1, 2001, and October 31, 2014, among a total of 1085 youths from Colorado. Statistical analysis was conducted from February 1, 2015, through August 31, 2017.

Study outcomes included nevus counts on all body sites, on body sites chronically exposed to the sun (ie, face, anterior neck, lateral forearms, dorsa of hands, and posterior neck on boys only), and on body sites intermittently exposed to the sun (ie, chest and abdomen, back and shoulders, lateral upper arms, legs, dorsa of feet, medial aspects of arms, palms, bottoms of feet, and posterior neck on girls only).2


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A total of 557 girls and 528 boys born in 1998 were included in the study; of the total, 13.8% (150 of 1085) were Hispanic. Median total body nevus counts increased linearly among non-Hispanic white girls and boys between ages 3 years (girls, 6.61 [95% CI, 5.96-7.33]; boys, 6.31 [95% CI, 5.66-7.03]) and 16 years (girls, 77.58 [95% CI, 72.68-82.81]; boys, 81.30 [95% CI, 75.95-87.03]).

The median total body nevus counts were lower among Hispanic white children (girls aged 16 years, 53.75 [95% CI, 45.40-63.62]; boys aged 16 years, 51.45 [95% CI, 44.01-60.15]) than among non-Hispanic white youths, but they followed a largely linear trend that varied according to sex.

Nevus counts on body parts that were chronically exposed to the sun increased over time, but leveled off at age 16 years. Moreover, nevus counts on body parts that are intermittently exposed to the sun followed a strong linear pattern in participants through age 16 years. Although Hispanic white girls and boys had similar nevus counts on sites that are intermittently exposed to the sun through age 10 years, increases after age 10 years were steeper for girls compared with boys, with nevus counts in this group exceeding those in boys aged 11 to 16 years.

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The investigators concluded that youths are at risk for the development of nevi beginning in early childhood and continuing through midadolescence. Thus, exposure to ultraviolet light during this period should be reduced, especially on those body sites intermittently exposed to the sun, where nevi can accumulate through age 16 years. Increased attention to sun protection is warranted in boys, because they accumulate more nevi overall compared with girls, and particularly in the adolescent years among girls.

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References

1. Asdigian NL, Barón AE, Morelli JG, et al. Trajectories of nevus development from age 3 to 16 years in the Colorado Kids Sun Care Program cohort [published online September 12, 2018]. JAMA Dermatol. doi: 10.1001/jamadermatol.2018.3027

2. Gallagher RP, McLean DI, Yang CP, et al. Anatomic distribution of acquired melanocytic nevi in white children: a comparison with melanoma: the Vancouver Mole Study. Arch Dermatol. 1990;126(4):466-471.