Background: Frequent exposure to ultraviolet light in early life has more detrimental and long-term effects on skin than in adulthood. Teenagers with strong sun-seeking behaviors may be more likely to use an indoor tanning bed than those who seek less sun, probably due to addictiveness of ultraviolet exposure. We aimed to examine associations between sun exposure behaviors and average annual indoor tanning usage frequency during high school/college in US females.
Methods: In this cross-sectional study, we used data from The Nurses' Health Study II, a large prospective cohort of US female nurses. We included a total of 81,746 white females who answered the average annual frequency of indoor tanning during high school/college. Our study exposures were average weekly time spent outdoors in a swimsuit and average percentage of time of wearing sunscreen at the pool or beach during their teenage years, average weekly hours spent outdoors in direct sunlight in daytime during high school/college, and the number of severe sunburns which blistered between ages 15-20. Main outcomes was average annual frequency of indoor tanning bed usage during high school/college.
Results: In multivariable-adjusted logistic regression, we demonstrated positive associations between the sun exposure behaviors and the indoor tanning habit. Specifically, teenagers who spent daily outdoors in a swimsuit (adjusted odds ratio [aOR], 95% confidence interval [CI] for daily vs. <1/week: 2.68, 1.76-4.09) or who had ≥ 10 sunburns that blistered (aOR, 95% CI for ≥ 10 vs. never: 2.18, 1.53-3.10) were more likely to use indoor tanning beds ≥ 12 times/year. Also, teenagers/undergraduates who spent ≥ 5hours/week outdoors in direct sunlight during daytime used indoor tanning ≥ 12 times/year (aOR, 95% CI: 2.18, 1.39-3.44) than those who spent < 1/week. However, there was not a significant association between average uses of sunscreen at the pool/beach and indoor tanning bed. Multivariable-adjusted linear regression models also showed similar results.
Conclusions: Teenagers who spent more time outdoors or got more sunburns tended to use indoor tanning more frequently. These findings provide evidence that teenagers with strong sun-seeking behaviors may have excessive exposure to artificial ultraviolet radiation as well.