Importance: There are limited data among young adults on sunscreen use during childhood and adulthood and on the association of sunscreen use with melanoma risk.
Objective: To assess correlates of early-life sunscreen use and the association between sunscreen use and risk of cutaneous melanoma before age 40 years.
Design, setting, and participants: This population-based, case-control family study analyzed Australian Melanoma Family Study data for persons with questionnaire data on sunscreen use collected by interview from 2001 to 2005 across 3 states in Australia, representing two-thirds of the country's population. Case participants (aged 18-39 years) had confirmed first primary melanoma. Siblings of case participants were included, and case participants without a sibling control were excluded. Unrelated controls (aged 18-44 years) were recruited from the electoral roll or were a spouse, partner, or friend nominated by case participants. Data analyses were conducted from October 2017 to February 2018.
Exposures: Self- and parent-reported sunscreen use, sun exposure, and other candidate risk factors during childhood and adulthood.
Main outcomes and measures: Logistic regression analyses adjusted for potential confounders were used to estimate odds ratios (ORs) for melanoma and for correlates of sunscreen use.
Results: Participation was 629 of 830 contactable cases (76%) (629 of 1197 overall [53%]), 240 of 570 contactable controls (42%) from the electoral roll (240 of 1068 overall [23%]), and 295 of 371 nominated spouse or friend controls (80%); analysis incuded 603 cases and 1088 controls. The median (interquartile range) age was 32 (28-36) years for 603 cases, 35 (30-38) years for 478 unrelated controls, and 34 (29-38) years for 610 sibling controls. There were more women than men (range, 57%-62%) in all groups, approximately 40% (range, 39%-43%) of participants had a university education, and most participants (range, 58%-73%) had British/northern European ethnicity. Risk of melanoma was less with higher use of sunscreen in childhood (OR for highest vs lowest tertiles, 0.60; 95% CI, 0.42-0.87; P = .02 for trend) and across the lifetime (OR, 0.65; 95% CI, 0.45-0.93; P = .07 for trend). Subgroup analyses suggested that the protective association of sunscreen with melanoma was stronger for people reporting blistering sunburn, receiving a diagnosis of melanoma at a younger age, or having some or many nevi. Total lifetime sun exposure was unrelated to melanoma risk (OR for highest vs lowest tertile, 0.97; 95% CI, 0.66-1.43; P = .94 for trend). By contrast, total sun exposure inversely weighted by sunscreen use (as a measure of sun exposure unprotected by sunscreen) was significantly associated with melanoma risk (OR, 1.80; 95% CI, 1.22-2.65; P = .007 for trend) and appeared stronger for people having lighter pigmentation or some or many nevi or using sunscreen to stay longer in the sun. Regular users of sunscreen were more likely to be female, younger, and of British or northern European ancestry and to have higher educational levels, lighter skin pigmentation, and a stronger history of blistering sunburn.
Conclusions and relevance: Our findings provided evidence that regular sunscreen use is significantly associated with reduced risk of cutaneous melanoma among young adults and identified several characteristics associated with less sunscreen use.