Sunscreen use is often proposed for sun protection because of their ability to block UV-induced sunburns (the sun protection factor -SPF). Among suntan seekers, however, risk of cutaneous melanoma may be increased because of extended sun exposure duration. We made a systematic review of the evidence linking sunscreen use to sun exposure duration. Five observational studies found that when sun exposure was associated with willingness to get a tan or to stay longer in the sun (i.e., intentional sun exposure), sunscreen use was associated with duration of sun exposure 13-39% longer. Paradoxically, sunburns tend to be more frequent among sunscreen users, probably because of greater natural sun sensitivity. When sun exposure was not intentional, sunscreen use did not increase time spent in the sun. Two European double-blind randomized trials conducted among young sun seekers found daily sun exposure duration, especially sunbathing, 19-25% longer with use of SPF 30 than with use of SPF 10 sunscreens. One randomized trial in a holiday resort in France found a 3-13% increase in sun exposure duration with use of SPF 12 versus SPF 40 sunscreen. But, the SPF 12 groups used 3.6-4.2 more sunscreen than the SPF 40 group, and thus the actual SPF in the SPF 12 group was higher than in the SPF 40 groups. In conclusion, sunscreen use leads to longer duration of sun exposure when sun exposure is intentional, but not when sun exposure is non intentional. ' 2007 Wiley-Liss, Inc.

Use of higher SPF sunscreen seems to increase the duration of recreational sun exposure of young white Europeans.

A large European case-control study investigated the association between sunbed use and cutaneous melanoma in an adult population aged between 18 and 49 years. Between 1999 and 2001 sun and sunbed exposure was recorded in 597 newly diagnosed melanoma cases and 622 controls in Belgium, France, The Netherlands, Sweden and the UK. Fifty three percent of cases and 57% of controls ever used sunbeds. The overall adjusted odds ratio (OR) associated with ever sunbed use was 0.90 (95% CI: 0.71-1.14). There was a South-to-North gradient with high prevalence of sunbed exposure in Northern Europe and lower prevalence in the South (prevalence of use in France 20%, OR: 1.19 (0.68-2.07) compared to Sweden, prevalence 83%, relative risk 0.62 (0.26-1.46)). Dose and lag-time between first exposure to sunbeds and time of study were not associated with melanoma risk, neither were sunbathing and sunburns (adjusted OR for mean number of weeks spent in sunny climates >14 years: 1.12 (0.88-1.43); adjusted OR for any sunburn >14 years: 1.16 (0.9-1.45)). Host factors such as numbers of naevi and skin type were the strongest risk indicators for melanoma. Public health campaigns have improved knowledge regarding risk of UV-radiation for skin cancers and this may have led to recall and selection biases in both cases and controls in this study. Sunbed exposure has become increasingly prevalent over the last 20 years, especially in Northern Europe but the full impact of this exposure on skin cancers may not become apparent for many years.