Watts CG, et al. - Researchers assessed the potential effect of sunscreen use in childhood and early adulthood on melanoma risk before 40 years of age, and identified possible factors associated with sunscreen use among Australian children and young adults in this population-based, case-control family study by analyzing the data of 603 patients and 1,088 control participants from the Australian Melanoma Family Study. They observed a significant link between regular sunscreen use and decreased risk of cutaneous melanoma among young adults. Several characteristics associated with less sunscreen use were also identified. Factors associated with sunscreen use were sex, age, ancestry, educational level, skin pigmentation, and sunburn.

Methods

• They examined the Australian Melanoma Family Study data for individuals with questionnaire data on sunscreen use collected by interview from 2001 to 2005 across three states in Australia, representing two-thirds of the country’s population.
• The first primary melanoma was confirmed by the case participants (aged 18-39 years).
• Siblings of case participants were involved in this analysis; case participants without a sibling control counterpart were excluded.
• Unrelated control participants (aged 18-44 years) were enlisted from the electoral roll or were a spouse, partner, or friend referred by case participants.
• From October 2017 to February 2018, the investigators performed data analyses w.
• Main exposures analyzed were self- and parent-reported sunscreen use, sun exposure, and other candidate risk factors during childhood and adulthood.
• To estimate odds ratios (ORs) for melanoma and for correlates of sunscreen use, they used logistic regression analyses adjusted for potential confounders.

Results

• Participation included 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 involved 603 cases and 1,088 controls.
• Researchers found that 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.
• Results revealed that there were a larger number of women than men (range, 57% to 62%) in all groups, ~40% (range, 39% to 43%) of participants had a university education, and most participants (range, 58% to 73%) were of British/northern European ethnicity.
• They noted that the 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=0.02 for trend) and across the lifetime (OR, 0.65; 95% CI, 0.45-0.93; P=0.07 for trend).
• According to the subgroup analyses, the protective relationship of sunscreen with melanoma was stronger for individuals reporting blistering sunburn, receiving a diagnosis of melanoma at a younger age, or having some or many nevi.
• They observed that total lifetime sun exposure was unrelated to melanoma risk (OR for highest vs lowest tertile, 0.97; 95% CI, 0.66-1.43; P=0.94 for trend).
• Findings suggested a significant association of total sun exposure inversely weighted by sunscreen use (as a measure of sun exposure unprotected by sunscreen) with melanoma risk (OR, 1.80; 95% CI, 1.22-2.65; P=0.007 for trend) and seemed stronger for individuals having lighter pigmentation or some or many nevi or using sunscreen to stay longer in the sun.
• They reported that regular users of sunscreen were more likely to be female, younger, of British or northern European ancestry, and to have higher educational levels, lighter skin pigmentation, and a stronger history of blistering sunburn.