Very few studies have been done on the relationship between sunbed use and non-melanoma skin cancer risk. Two hospital-based case-control studies in Ireland, in the mid to late 1980s, did not show any relationship between the use of tanning devices and non-melanoma skin cancer (O’Loughlin et al, 1985; Herity et al, 1989). A similar conclusion, at about the same time, was reached by Bajdik et al (1996) in British Columbia, Canada, who evaluated 406 controls (population based) against 180 SCC cases and 226 BCC cases. About 10% of each group had “ever” used a sunlamp. The adjusted OR for BCC and SCC for “ever” having used a sunlamp were 1.2 (0.7-2.2) and 1.4 (0.7-2.7) respectively, which are clearly non-significant. One small study from 2002, using the “generalized estimating equation method” reported no significant effect of tanning devices for BCC, even though the total lifetime exposure to tanning devices was almost twice as high in patients compared with controls (Boyd et al, 2002). In the same year, Karagas et al (2002) assessed the relationship between use of tanning devices and BCC and SCC in a population-based case control study. In this study there was greater use of tanning devices ranging from 9.2% (male controls) to 28.4% (female patients). The OR for BCC and SCC were 1.5 (1.1-2.1) and 2.5 (1.7-3.8) respectively and adjustment for a variety of factors made no difference to these results. The results of Karagas et al (2002) indicated that the use of tanning devices is a risk factor for non-melanoma skin cancer.
Sunbed usage has increased considerably in recent years (Rafnsson et al, 2004) but the data on melanoma risk are scanty. There are a number of case-control studies but the details on exposure for the majority was small and all, as case-control studies, were subject to bias of recall and the effect of confounders. There is a single cohort study (Verierod et al, 2003) in which risk of melanoma was addressed. A number of case-control studies reported no evidence of sunbed use as a risk factor for melanoma (Osterlind et al, 1988; Holly et al, 1995; Westerdal et al, 1994; Zanetti et al, 1988; Chen et al, 1998; Dunn-Lane et al, 1993; Naldi et al, 2000; Bataille et al 2004, 2005). The majority of these studies were, however, small and the prevalence of sunbed usage in cases and controls was very low. Others were supportive of weak evidence or evidence in “at risk” groups (Walter et al, 1990; Westerdahl et al, 2000). Walter et al (1990) showed some suggestion of a trend to increased risk of melanoma with longer duration of use. In the study by Westerdahl et al (2000) an increased risk of melanoma was demonstrated only for use of sunbeds before the age of 35 years (OR, 2.3; CI, 1.2–4.2). Swerdlow et al (1988) showed a significantly increased risk for any use of sunbeds OR 2.94 (95% CI 1.4-6.17) with a significant trend for increased duration of use. Autier et al (1994) showed little evidence of risk overall when corrected for skin type etc but did show evidence of increased risk for usage of sunbeds for 10 hours or more, when burning was reported after use of the sunbed or when the users reported use of the sunbed to tan.
The only cohort study to address risk associated with solaria followed more than 100,000 Norwegian and Swedish women for an average of 8 years, and 187 melanomas developed. This study identified use of a solarium for 1 or more times per month as a risk factor for melanoma. When the exposures occurred between the ages of 20 – 29 years the adjusted relative risk was 2.58 (95%CI 1.48-4.50). Among women who had used a solarium once or more per month, in at least one of the three decades between ages 10 and 39, the adjusted relative risk of melanoma compared to women that had never or rarely used a solarium during these three decades, was 1.55 (95%CI 1,4-2.32) (Veierød et al, 2003). This is probably the most persuasive evidence for a role for sunbeds in causing melanoma but the data are as yet relatively weak and support the view only that frequent use is deleterious.
Gallagher et al (2005) carried out a meta-analysis of 9 case-control studies and the one cohort study and came to the conclusion that sunbed use significantly increased the risk of melanoma with an OR of 1.25 (1.1-1.5) “ever” versus “never” used. This increased to 1.69 (1.3 –2.2) using the metric “first exposure as a young adult”.
There seems to be no published literature on the photoageing effects of sunbed use but this would be expected from the long-term use of sunbeds because photoageing is associated with solar exposure (Fisher et al, 2002). Some studies have looked at the effect of repeated sub- erythemal exposure of UVB and UVA in human skin and reported some changes that are associated with photoageing (Lavker et al, 1995a, 1995b; Lavker and Kaidby, 1997).
As with the sun, tanning devices emit infrared radiation (IR: 760nm to 1mm). The effects of IR on skin are poorly understood but in vitro studies suggest that it may play a role in photoageing, which has been suggested by animal studies (Schieke et al, 2003).
Effects on the eye
Four studies have assessed the relationship between sunbed use and ocular melanoma and found varying degrees of association Tucker et al, 1985; Seddon et al, 1990; Holly et al, 1996). The most recent study (Vajdic et al, 2004) provides “moderately strong” evidence, with several metrics, that sunbed use results in ocular melanoma, after adjustment for confounding factors including exposure to solar radiation. The OR for use (never vs ever) was 1.7 (95% CI 1.0 – 2.8) and 2.4 (95% CI 1.0 – 6.1) for first use under 21 years. There was a significant trend (p = 0.04) for duration of use. This study also suggested a protective effect from wearing goggles with an OR = 2.2 (95% CI 0.5 - 9.7) in those who did not always wear goggles but this was not significant (p = 0.3).