Twenty-three epidemiological studies (i.e, studies of disease patterns in actual human populations) have been published looking for a potential link between indoor tanning and melanoma.
Of these 23 studies, 18 failed to report any association between indoor tanning and melanoma.
As summarized below, the remaining five studies suffer from a variety of defects:
- Adam et al. (1981). This study was designed to study an association between oral contraceptives and melanoma, not indoor tanning and melanoma. The reported data for melanoma can only be regarded as an artifact of the study.
- Swerdlow et al. (1988). This study had only 38 cases of melanoma who claimed to have been exposed to indoor tanning and exposure data were self-reported. Also, key confounding risk factors were not analyzed such as family history of melanoma.
- Autier et al. (1991). Little confidence in this loosely conducted “descriptive” study was offered by the authors themselves. They concluded the study only showed the need for more research. Follow-up studies by Autier published in 1994 and 2005 reported no association between indoor tanning and melanoma.
- Westerdahl et al. (2000). This was a small study (only 88 cases of melanoma in its touted result) that falls within the range of epidemiologic noise (i.e., an increase in risk of less than 100%). Also of note, the dose-response curve entirely failed at high levels of tanning bed use.
- Lazovich et a. (2010). The key association is within the noise range of epidemiology (i.e., reported risks of less than 100%). An interesting aspect of this study is that for melanoma risk factors that are verifiable (i.e, hair color, skin color, number of moles), the reported associations are relatively strong. However, for the risk factor that is not verifiable (i.e., UV exposure), the reported associations are in the noise range.
If the proposition that indoor tanning caused melanoma was true then, excepting extenuating circumstances, all studies should clearly report the existence of the association.