Affiliations of authors: Division of Epidemiology, University of Minnesota, Minneapolis (DL, CS); Dermatoepidemiology Unit, Department of Veterans Affairs Medical Center, Providence, RI (MAW); Department of Dermatology, Rhode Island Hospital and Brown University, Providence (MAW); Department of Epidemiology and Biostatistics, Memorial Sloan-Kettering Cancer Center, New York, NY (MB).
Correspondence to: DeAnn Lazovich, PhD, Division of Epidemiology, University of Minnesota, 1300 S. 2nd Ave., #300, Minneapolis, MN 55454 (e-mail: lazovich{at}epi.umn.edu)
The results obtained in at least 24 casecontrol studies that have examined the association between indoor tanning and melanoma are largely inconclusive (1). The study by Veierød et al. (2) is important because it provides the first prospective evidence for an association between indoor tanning and melanoma and it includes data reflecting recent exposures to modern tanning devices. The authors reported on women who were aged 3050 years when they completed questionnaires in 1991 or 1992 about their use of tanning devices during 10-year age periods, up to age 49 years. The authors presented an analysis stratified by the age periods and reported that the strongest associations between melanoma and indoor tanning were among women who reported using a tanning device when they were between the ages of 20 and 29. We would like to suggest that Veierød et al. perform an analysis in which they consider the calendar year of use of tanning devices.
For example, in the United States, indoor tanning devices that emitted greatly reduced UVB relative to UVA radiation became available around 1980 (3). These devices allowed users to have longer exposures with less burning and gave rise to the indoor tanning industry that operates today. Although UVB is thought to be more carcinogenic than UVA because the observed action spectra for direct DNA damage (erythema in humans and skin cancer in mice) are in that range, UVA exposure may also be an important factor in melanoma development (4). To date, only one casecontrol study has included subjects with substantial exposure to these modern tanning devices; that study (5) reported an odds ratio for melanoma of 1.8 (95% confidence interval [CI] = 1.2 to 2.7) for regular users of tanning devices. In a population survey conducted in Minnesota in 2002, we found that 10% of individuals who had tanned indoors reported doing so prior to 1980 and, even among those who were age 30 or older in 1980, the majority initiated indoor tanning after 1980 (Lazovich D, Sweeney C, Forster J: unpublished data). We suspect that a similar period effect may be operating in the study by Veierød et al. because of the low prevalence of exposure reported by women for the 1019 and 2029 age periods. Veierød and colleagues observed an estimated relative risk of 2.58 (95% CI = 1.48 to 4.50) associated with the use of tanning devices at least once per month relative to no use among women when they were 2029 years old; their study population included a substantial proportion of women who attained that age prior to 1980. Thus, assuming that the availability of modern tanning devices in Sweden and Norway parallels that in the United States, an examination of the data by calendar year of use would allow readers to consider whether the estimated relative risk of 2.58 reflects exposure to higher UVB-emitting devices in the more distant past among older women or exposure to higher UVA-emitting devices more recently among younger women.
REFERENCES
1 Swerdlow AJ, Weinstock MA. Do tanning lamps cause melanoma? An epidemiologic assessment. J Am Acad Dermatol 1998;38:8998.[ISI][Medline]
2 Veierød MB, Weiderpass E, Thorn M, Hansson J, Lund E, Armstrong B, et al. A prospective study of pigmentation, sun exposure, and risk of cutaneous malignant melanoma in women. J Natl Cancer Inst 2003;95:15308.
3 Spencer JM, Amonette R. Tanning beds and skin cancer: artificial sun + old sol = real risk. Clin Dermatol 1998;16:487501.[CrossRef][ISI][Medline]
4 Wang SQ, Setlow R, Berwick M, Polsky D, Marghoob AA, Kopf AW, et al. Ultraviolet A and melanoma: a review. J Am Acad Dermatol 2001;44:83746.[CrossRef][ISI][Medline]
5 Westerdahl J, Ingvar C, Masback A, Jonsson N, Olsson H. Risk of cutaneous malignant melanoma in relation to use of sunbeds: further evidence for UV-A carcinogenicity. Br J Cancer 2000;82:15939.[CrossRef][ISI][Medline]
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