Objective: High-protection sunscreens have been suspected to prompt people to increase sun exposure, and thus to increase skin cancer risk. We tested the influence of both the actual protection (sun protection factor [SPF]) and the information about protection (label) on sun-exposure behavior.
Design: Randomized controlled trial.
Setting: Four French seaside resorts during summer 2001.
Participants: A total of 367 healthy subjects during their 1-week holiday. Outcome was assessable in 98% of them.
Intervention: Subjects were offered free sunscreens, with randomization into the following study arms: (1) SPF 40 labeled as "high protection"; (2) SPF 40 labeled as "basic protection"; and (3) SPF 12 labeled as "basic protection." Arm 4, ie, SPF 12 labeled as "high protection," was not implemented for ethical reasons. Subjects were not aware of the real target of the study and were blinded to the SPF value.
Main outcome measure: Duration of sunbathing exposure during 1 week. Secondary outcomes were occurrence of sunburns and amount of sunscreen used. Influences of SPF and label were assessed separately.
Results: Compared with the low-SPF group, the high-SPF group did not have longer sunbathing exposure (12.9 +/- 7.2 h/wk for high SPF vs 14.6 +/- 6.7 h/wk for low SPF; P = .06), experienced fewer sunburns (14% vs 24%; P = .049), and used less sunscreen (median, 30 g vs 109 g; P<.001). The label "high protection" or "basic protection" had no influence on these end points.
Conclusions: In this adult population, higher SPF had no influence on duration of sun exposure and offered better protection against sunburns. Although higher SPF may increase sun exposure duration in specific populations, this effect cannot be viewed as a universal side effect of high-SPF sunscreens.