Sun Exposure, Sun Protection, and Vitamin D

Objectives: To examine during what behaviors people apply sunscreen and to assess the relationship to UV exposure monitored by personal dosimetry and diaries.Design: Open prospective observational study.Setting: University hospital.Participants: A convenience sample of 340 Danish volunteers: children, adolescents, indoor workers, sun worshippers, golfers, and gardeners (age range, 4-68 years).Intervention: Subjects recorded sunscreen use and sun-exposure behavior in diaries and carried personal, electronic UV dosimeters, measuring time-stamped UV doses continuously, during a median of 119 days covering 346 sun-years (1 sun-year equals 1 subject participating during 1 summer season).Main Outcome Measures: Associations between sunscreen use and age, sex, skin type, occupation, sunburn, UV exposure doses, and behavior; and adequate application density and sun protection factor required to prevent sunburn.Results: There were great variations in sunscreen use, which was highly correlated with risk behavior (sunbathing or exposing the upper body) (r = 0.39; P<.001). Sunscreens were used on a median of 5 days per sun-year (range, 1 day for gardeners to 16 days for sun worshippers). Ten percent of females and 41% of males never used sunscreens. Females used sunscreens more but also had more unprotected risk behavior than males (8 days vs 4 days; P<.001). Sunscreen use was not correlated with age, and children had as much unprotected risk behavior as adults. Sunscreens were used on 86% of the days with risk behavior in southern Europe vs 20% in northern Europe (P<.001). The UV doses were significantly higher on days with sunscreen (P≤.03) and on sunburn days (P<.001). The median sun protection factor was 10.5. The sun-protecting effect corresponded to an application density of 0.5 mg/cm2.Conclusions: Days with sunscreen correlated not with days without risk behavior, but with days “sunbathing with the intention to tan,” indicating that sunscreens were used as tanning aids to avoid sunburn.