Women who accumulated more indoor tanning sessions over time significantly increased their risk for squamous cell cancer over women who never engaged in indoor tanning, based on data from 159,419 women.
Previous research has examined associations between indoor tanning and cutaneous melanoma, but an association between indoor tanning and squamous cell carcinoma (SCC) has not been well studied, wrote Simon Lergenmuller, MSc, of the University of Oslo, and colleagues.
In a prospective cohort study published in JAMA Dermatology, the researchers surveyed 159,419 women from the Norwegian Women and Cancer study. Of these, 95,552 women (69%) reported ever use of indoor tanning. The average age at study inclusion was 50 years. During an average of 17 years’ follow-up, 597 women developed SCC.
Overall, the risk of SCC increased with increasing numbers of indoor tanning sessions. The adjusted hazard ratio for most tanning sessions versus no tanning sessions was 1.83. “The association between cumulative exposure to indoor tanning and SCC risk was the same regardless of duration of use and age at initiation,” the researchers wrote.
The risk of SCC was significantly higher both among women with 10 years or less of tanning bed use and among those with more than 10 years of use, compared with never users (HRs, 1.41 and 1.43, respectively). Similarly, researchers found a significantly higher risk of SCC among women who started indoor tanning at age 30 years or older and those who started younger than 30 years, compared with never users (HRs, 1.36 and HR, 1.51, respectively).
No significant association appeared between age at initiation of indoor tanning and age at the time of SCC diagnosis.
The study findings were limited by several factors including the variation in UV radiation among tanning devices, the lack of data on men, and the retrospective collection of UV exposure data that likely led to some misclassification, the researchers noted.
However, the results were strengthened by the large sample size and support the association between increased exposure to indoor tanning and increased risk of SCC, they wrote. “Avoidance of indoor tanning may help prevent not only melanoma but also SCC, and our results support the development of policies that regulate indoor tanning.”
The study was supported by the Institute of Basic Medical Sciences, University of Oslo, and the Norwegian Cancer Society. The researchers had no financial conflicts to disclose.
SOURCE: Lergenmuller S et al. JAMA Dermatol. 2019 Oct 2. doi: 10.1001/jamadermatol.2019.2681.