Elsevier

Cancer Epidemiology

Volume 59, April 2019, Pages 1-7
Cancer Epidemiology

Indoor tanning and skin cancer in Canada: A meta-analysis and attributable burden estimation

https://doi.org/10.1016/j.canep.2019.01.004Get rights and content

Highlights

  • Over 10% of Canadian adults used an indoor tanning device in the past year and over a quarter had used an indoor tanning device in their lifetime.

  • 7.0% of melanomas, 5.2% of basal cell carcinomas, and 7.5% of squamous cell carcinomas in Canada in 2015 were attributable to indoor tanning.

  • The proportion of melanoma and non-melanoma skin cancer cases in Canada attributable to indoor tanning was greatest among young women.

Abstract

Background

Consistent epidemiologic and experimental studies have demonstrated that UV-emitting tanning devices cause melanoma and non-melanoma skin cancer. The purpose of this study was to estimate the relative risk of skin cancer associated with the use of indoor tanning devices relevant to Canada, to estimate the proportion and number of skin cancers in Canada in 2015 that were attributable to indoor tanning, and to explore differences by age and sex.

Methods

Skin cancer cases attributable to the use of an indoor tanning devices were estimated using Levin’s population attributable risk (PAR) formula. Relative risks for skin cancer subtypes that were relevant to Canada were estimated through meta-analyses and prevalence of indoor tanning was estimated from the 2006 National Sun Survey. Age- and sex-specific melanoma data for 2015 were obtained from the Canadian Cancer Registry, while estimated NMSC incidence data were obtained from the 2015 Canadian Cancer Statistics report.

Results

Ever use of indoor tanning devices was associated with relative risks of 1.38 (95% CI 1.22–1.58) for melanoma, 1.39 (1.10–1.76) for basal cell carcinoma (BCC), and 1.49 (1.23–1.80) for squamous cell carcinoma (SCC). Overall, 7.0% of melanomas, 5.2% of BCCs, and 7.5% of SCCs in 2015 were attributable to ever of indoor tanning devices. PARs were higher for women and decreased with age.

Conclusion

Indoor tanning contributes to a considerable burden of skin cancer in Canada. Strategies aimed at reducing use should be increased and a total ban or restrictions on use and UV-intensity should be considered by health regulators.

Introduction

Incidence rates of cutaneous malignant melanoma and non-melanoma skin cancer (NMSC) in Canada have been steadily increasing between 1986 and 2010 [1]. The estimated age standardized incidence rate for melanoma in 2017 was 18.5 cases per 100,000 (7300 cases) [2] and 198.4 for NMSC (78,300 cases) in 2015 [3]. Melanoma is the most deadly form of skin cancer, and has become one of the most common cancers among young adults in Canada, particularly for females [1]. Of NMSC cases, approximately 77% are basal cell carcinoma (BCC) and 23% are squamous cell carcinoma (SCC) [1]. Although rarely fatal, the high incidence of NMSC represents a significant burden of disease in terms of morbidity, quality of life, social impact, and health care costs [4].

There is consistent epidemiologic evidence that indoor tanning causes melanoma and non-melanoma skin cancer (NMSC) and in 2012 the International Agency for Research on Cancer (IARC) classified artificial sources of ultraviolet radiation as carcinogenic (class 1) to humans [5]. Indoor tanning is similar to sun exposure for ultraviolet B (UVB) radiation exposure, but is 10–15 times stronger than sun exposure for ultraviolet A (UVA) radiation [6]. With longer wavelengths than UVB radiation, UVA rays penetrate more deeply into the skin than UVB, and can cause mutations in tumor suppressor genes or other oncogenes, both directly through DNA damage and indirectly through oxidative stress [7]. Moreover, UVA has been shown to be relatively ineffective at inducing pigmentation changes that can attenuate the potentially damaging effects of future exposure to UVR, as UVB does [8]. Additionally, indoor tanning devices have been shown to induce harmful burns, which an estimated two-thirds of users experience at least once [9]. While indoor tanning devices in Europe are limited in intensity to an ultraviolet index of 12, Canada and the USA do not place restrictions on owners or users [10]. In addition, there is some evidence that the risk of skin cancer associated with ever use of indoor tanning devices is greater in North America than in Europe [11], which could be a reflection of varying use patterns and device restrictions.

Population attributable risks (PAR) for skin cancer associated with indoor tanning have previously been estimated for Europe [12,13], France [14], Australia [13], and the United States [13], but not for Canada. Two main limitations of these previous studies is that they did not restrict the studies included in the PAR estimates for ever use of indoor tanning devices to those with a relevant exposure distribution to their own population, and they included studies that did not control for confounding from exposure to solar UVR exposure. Therefore, not only does a Canadian estimate require an exposure distribution for Canada, but it also requires a relative risk estimate that is applicable to the types of devices and usage patterns which represent Canadian indoor tanning exposure.

While Brazil and Australia have banned indoor tanning devices [10], Canada only restricts use to those over the age of 18 [15]. In addition, indoor tanning users in Canada are required to wear protective glasses and all commercial equipment must display labels that detail the health risks of indoor tanning, including that it can cause cancer [15]. However, minors can still use tanning devices with signed consent from a guardian, and restriction in terms of intensity, frequency, or duration of use are not mandated in Canada [15]. Therefore, attributable burden estimates have important implications for policy and preventive initiatives aimed at reducing the burden of skin cancer in Canada. Thus, the objective of this study was to estimate the risk of skin cancer associated with the ever use of indoor tanning devices that is relevant to Canada and to quantify the proportion and number of skin cancer cases in Canada that could be attributed to indoor tanning in 2015. A secondary objective included exploring the extent to which PAR estimates varied by age, sex, and province.

Section snippets

Materials and methods

This manuscript is part of The Canadian Population Attributable Risk of Cancer (ComPARe) study – a project aimed at quantifying the number and proportion of cancer cases in Canada, now and in the future, that could be prevented through changes in the prevalence of modifiable exposures associated with cancer. The methods for this study have previously been described [16].

The proportion and number of skin cancer cases in Canada that occurred in 2015 that were attributable to the use of indoor

Estimated risk of skin cancer associated with indoor tanning

We identified 759 unique studies in the initial PubMed search (Fig. 1). Thirty-nine studies from the PubMed search and 18 additional studies identified from reference lists and secondary sources underwent full-text review. After full-text screening and applying our exclusion criteria, 11 studies examining the association of indoor tanning with at least one of the skin cancer subtypes were included in the quantitative analysis. The primary reasons for exclusion were a lack of control for

Discussion

In this study, patterns of indoor tanning use relevant to Canada were associated with a relative risk of 1.38 for melanoma, 1.39 for basal cell carcinoma, and 1.49 for squamous cell carcinoma. Overall, we estimated that 7.0% of melanomas, 5.2% of BCCs, and 7.5% of SCCs in Canada in 2015 were attributable to the use of indoor tanning devices. In addition, we found that there were considerable differences in PAR estimates by age, sex, and province. In particular, PAR estimates were highest for

Conclusion

The rates of skin cancer in Canada have been consistently increasing over time and in this study we estimate that 7.0% of melanomas, 5.2% of BCCs, and 7.5% of SCCs in Canada in 2015 are attributable to indoor tanning. Given that indoor tanning is one of the risk factors for skin cancer that is most amenable to change through policies that limit or restrict use, strategies aimed at reducing use should be increased and a total ban or restrictions on use and UV-intensity should be considered by

Authorship contribution statement

DO’S, DRB, PAD, PJV, CMF, and WDK were responsible for the study conception and contributed substantially to the study design. DO’S, DRB, and WDK drafted the manuscript. DO’S, DRB, PAD, PJV, CMF, and WDK revised the draft paper and gave final approval of this version to be accountable for all aspects of the work in ensuring that questions related to accuracy or integrity of any part of the work are appropriately investigated and resolved.

Conflicts of interest

No conflicts of interest exist.

Funding

This research is supported by a Canadian Cancer Society Research Institute Partner Prevention Research Grant (#703106).

Acknowledgements

Dylan O’Sullivan is supported by a Queen Elizabeth II Scholarship and an Empire Life Fellowship. Darren Brenner holds a Canadian Cancer Society Prevention Capacity Development Award (#703917). Christine Friedenreich is supported by an Alberta Innovates Health Solutions Health Senior Scholar Award and by the Alberta Cancer Foundation Weekend to End Women’s Cancers Breast Cancer Chair.

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  • Cited by (0)

    1

    Stephen D. Walter, Department of Health Research Methods, Evidence, and Impact, McMaster University, Hamilton, Ontario, Canada, Eduardo L. Franco, Departments of Oncology and Epidemiology, Biostatistics and Occupational Health, McGill University, Montréal, Québec, Canada, Abbey E. Poirier, Department of Cancer Epidemiology and Prevention Research, Cancer Control Alberta, Alberta Health Services, Calgary, Alberta, Canada, Yibing Ruan, Department of Cancer Epidemiology and Prevention Research, Cancer Control Alberta, Alberta Health Services, Calgary, Alberta, Canada, Xin Grevers, Department of Cancer Epidemiology and Prevention Research, Cancer Control Alberta, Alberta Health Services, Calgary, Alberta, Canada, Prithwish De, Cancer Care Ontario, Toronto, Ontario, Canada, Leah Smith, Canadian Cancer Society, Toronto, Ontario, Canada, Rob Nuttall, Canadian Cancer Society, Toronto, Ontario, Canada, Perry Hystad, College of Public Health and Human Sciences, Oregon State University, Corvallis, Oregon, United States, Karena Volesky, Departments of Oncology and Epidemiology, Biostatistics and Occupational Health, McGill University, Montréal, Québec, Canada, Elizabeth Holmes, Canadian Cancer Society, Toronto, Ontario, Canada, Zeinab El’Masri, Cancer Care Ontario, Toronto, Ontario, Canada, Mariam El-Zein, Department of Oncology, McGill University, Montréal, Québec, Canada, Tasha Narain, Department of Public Health Sciences, Queen’s University, Kingston, Ontario, Canada, Priyanka Gogna, Department of Public Health Sciences, Queen’s University, Kingston, Ontario, Canada.

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