Study confirms link between indoor tanning and skin cancer risk

Indoor tanning increases the risks of developing non-melanoma skin cancer (known as basal cell carcinoma and squamous cell carcinoma), particularly among those exposed before the age of 25, finds a study published on bmj.com today.

It follows a BMJ study published in July that showed 3,438 (5.4%) new cases of melanoma diagnosed each year in Western Europe are related to sunbed use, particularly among young adults.

Some experts are now calling for Europe to follow the example of the United States by introducing a "tan tax" on indoor tanning salons.

The researchers, led by Professor Eleni Linos at the University of California San Francisco, estimate that indoor tanning may account for over 170,000 cases of non-melanoma skin cancer in the US alone.

Cases of non-melanoma skin cancer have increased dramatically over the last few decades. Although not as lethal as melanoma, they affect a vast number of people worldwide and are a substantial financial burden to healthcare systems. Several studies have examined the link between non-melanoma skin cancer and indoor tanning, but have yielded varied results.

So Professor Linos and her team set out to review the evidence. They analysed the results of 12 studies involving 9,328 cases of non-melanoma skin cancer (7,645 basal cell carcinomas and 1,683 squamous cell carcinomas).

Ever using indoor tanning was associated with a 67% higher risk of developing squamous cell carcinoma and a 29% higher risk of developing basal cell carcinoma, compared with never using it. Given the extent of indoor tanning use in the United States, the researchers estimated that such tanning accounts for 3.7% of cases of basal cell carcinoma and 8.2% of cases of squamous cell carcinoma. This corresponds to 98,408 cases of basal cell carcinoma and 72,244 cases of squamous cell carcinoma, making 170,652 cases of non-melanoma skin cancer each year attributable to indoor tanning.

Exposure at a young age (before 25 years) was significantly associated with an increased risk for basal cell carcinoma and showed a non-significant increased risk for squamous cell carcinoma. "This suggests a critical period for exposure during early life and a potential dose-response effect," say the authors.

Further analysis of the data, and adjustment for factors that may have affected the results, did not substantially alter the findings.

The authors say their findings point to a possible causal link between indoor tanning and non-melanoma skin cancers and they estimate that indoor tanning "may account for hundreds of thousands of new cases each year in the United States alone."

They conclude: "We hope that these findings can support public health campaigns and motivate increased regulation to reduce exposure to this carcinogen, especially during early life."

In an accompanying editorial, experts from the Queensland Institute of Medical Research in Australia say these two new reviews "provide more convincing evidence that exposure to artificial ultraviolet radiation is a cause of the three main skin cancers."