Context: High nevus density is a risk factor for cutaneous malignant melanoma. Melanocytic nevi originate in childhood and are largely caused by solar exposure.
Objective: To determine whether use of broad-spectrum, high-sun protection factor (SPF) sunscreen attenuates development of nevi in white children.
Design: Randomized trial conducted June 1993 to May 1996.
Setting and participants: A total of 458 Vancouver, British Columbia, schoolchildren in grades 1 and 4 were randomized in 1993. After exclusion of nonwhite children and those lost to follow-up or with missing data, 309 children remained for analysis. Each child's nevi were enumerated at the start and end of the study in 1996.
Intervention: Parents of children randomly assigned to the treatment group (n=222) received a supply of SPF 30 broad-spectrum sunscreen with directions to apply it to exposed sites when the child was expected to be in the sun for 30 minutes or more. Children randomly assigned to the control group (n=236) received no sunscreen and were given no advice about sunscreen use.
Main outcome measure: Number of new nevi acquired during the 3 years of the study, compared between treatment and control groups.
Results: Children in the sunscreen group developed fewer nevi than did children in the control group (median counts, 24 vs 28; P=.048). A significant interaction was detected between freckling and study group, indicating that sunscreen use was much more important for children with freckles than for children without. Modeling of the data suggests that freckled children assigned to a broad-spectrum sunscreen intervention would develop 30% to 40% fewer new nevi than freckled children assigned to the control group.
Conclusions: Our data indicate that broad-spectrum sunscreens may attenuate the number of nevi in white children, especially if they have freckles. JAMA. 2000.