A Prospective Cohort Study Exploring the Joint Influence of Sunlight Exposure and Tanning Bed Use on Basal Cell Carcinoma, Squamous Cell Carcinoma, and Melanoma Risk

TL;DR

This study finds that combining high sunlight exposure with tanning bed use in young adulthood increases the risk of basal cell carcinoma.

Contribution

The study identifies a synergistic effect between natural sunlight exposure and tanning bed use on basal cell carcinoma risk.

Findings

High sunlight exposure and tanning bed use in early life increased BCC risk by 53%.

Severe sunburns and tanning bed use in youth increased BCC risk by 62%.

No significant interaction was found for SCC or melanoma.

Abstract

Exposure to solar ultraviolet (UV) radiation and use of UV-emitting tanning devices are known risk factors for skin cancer. Few studies have explored the interaction between these risk factors, namely how the risk of skin cancer increases among those who both have been exposed to high levels of natural sunlight and regularly use tanning beds. Nurses’ Health Study II followed 116,430 women, aged 25–42, from 1991 to 2011. Cumulative average UV exposure was based on participants’ residences at follow-up periods. History of severe sunburn during ages 15–20 was used as a proxy for early-life sunlight exposure. Tanning bed use in early life data was collected. Participants reported melanoma, basal cell carcinoma (BCC), and squamous cell carcinoma (SCC) diagnoses. We built multivariable Cox regression models to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) for risk of skin cancer associated with joint effects of sunlight exposure and tanning bed use. Participants with high sunlight exposure and tanning bed use during high school/college had an increased risk of BCC (HR=1.53, CI 1.37–1.71, P interaction =0.01; vs. low UV exposure and no tanning bed use). Participants with a history of severe sunburns and tanning bed use during high school/college were at increased risk of BCC (HR=1.62, CI 1.47–1.79, P interaction =0.02; vs. no sunburns and no tanning bed use). No significant interactions were found between sunlight exposure and tanning bed use on SCC and melanoma risk. We found significant interactions between sunlight exposure and tanning bed use on the risk of BCC.