A new study has found that Australians, aged between 18 and 40 years, who applied sunscreen regularly since childhood, were 40% less likely to develop melanoma than those who rarely used sunscreen[i]. The study also found reduced risk in those who used more sunscreen throughout their lifetime than in those who rarely used sunscreen.
Melanoma and Occupational Exposure to Sunlight
Melanoma is a common and dangerous type of skin cancer. In the UK, it is the 5th most common cancer, with 13,500 cases diagnosed and 2,000 deaths recorded each year. It is widely known to be associated with exposure to sunlight, particularly sudden intense exposures.[ii]
In general, studies and reviews of the relationship between melanoma and sunlight suggest that intermittent exposure to sunlight is associated with an increased risk of melanoma, while regular heavy exposure, such as outdoor employment, is associated with a decreased risk, or no change in risk. Some studies have found a weak association with total sun exposure, but many have found no association with total exposure.
Studies in farmers have found an increased risk. One study distinguished that younger farmers are at increased risk, which decreases with age. Other studies have found no increase in risk for outdoor workers compared to indoor workers.
In unrelated research, results have indicated that head and neck melanomas have stronger associations with total sun exposure, while trunk melanomas have stronger associations with episodes of sunburn. These findings are inconsistent with more recent studies and reviews, which have found no difference in risk at different anatomical sites. In addition, incidence of melanoma at different body sites appears to differ by sex. Studies have also reported that melanomas at different sites present different genetic mutations, which suggests that there are different mechanisms of melanoma development.
The body of evidence associating sunlight exposure and melanoma infers that the relationship may not be simple.
The Royal Mail Group offers wide-brimmed hats, long-sleeved tops and long trousers to its employees, as protection from the sun. The Group does not provide sunscreen, because research has shown that offering sunscreen can lead to more sun risk-taking activity, e.g. relying exclusively on sunscreen for protection, choosing not to cover up and forgetting to apply sunscreen regularly[iii].
The Australian Study
This is the first study to examine the association between sunscreen use and melanoma risk in people under the age of 40 years[iv].
The study involved analysis of data from 603 melanoma patients and 1,088 non-melanoma patients, who participated in the Australian Melanoma Family Study. Some of the controls were siblings of the patients, and some were unrelated. The participants completed questionnaires to provide information about their use of sunscreen, sun exposure and other factors.
Results showed that the risk of melanoma was 40% lower in the top third of childhood sunscreen users compared to the bottom third. For overall lifetime users of sunscreen, the risk of melanoma was 35% lower in the top third than the bottom third. Further analysis suggested that the protective effect of sunscreen was stronger in users who reported blistering sunburn, received a diagnosis of melanoma at a younger age, or had ‘some or many’ moles. In addition, total lifetime sun exposure was unrelated to the risk of melanoma; the risk was the same, irrespective of sun exposure levels.
However, when total sun exposure and sunscreen use were considered together, taking into account the total unprotected sun exposure, the risk of melanoma increased by 80% in the top third of sun exposed participants. The greatest increase in risk of melanoma was observed in those with lighter skin pigmentation, those with ‘some or many’ moles, and those who used sunscreen to stay in the sun for longer periods of time.
The study also investigated which demographic groups were more likely to use sunscreen. The researchers found that regular users were female, younger, had British or Northern European ancestry, higher educational levels, lighter skin pigmentation and a stronger history of blistering sunburn.
This study may be of interest to those who employ outdoor workers. Although the findings relate primarily to the use of sunscreen during childhood, there was also evidence that persistent sunscreen use throughout life can reduce the risk of melanoma. This is in spite of Royal Mail Group claims that the provision of sunscreen would cause its employees to take more risks when exposed to sunlight.
[i] Watts, C. G. et al. Sunscreen Use and Melanoma Risk Among Young Australian Adults. JAMA Dermatol (2018). doi:10.1001/jamadermatol.2018.1774 https://jamanetwork.com/journals/jamadermatology/article-abstract/2687549 (Accessed 30 July 2018)
[ii] Skin cancer (melanoma). NHS choices. https://www.nhs.uk/conditions/melanoma-skin-cancer/ (Accessed 30 July 2018)
[iii] Royal Mail – Delivering a new sun safety strategy. IOSH NTTL. https://www.notimetolose.org.uk/about-the-campaign/good-practice-case-studies/royal-mail-delivering-new-sun-safety-strategy/ (Accessed 12 June 2018)
[iv] Sunscreen reduces melanoma risk by 40 per cent in young people. Science Daily 19 July 2018. https://www.sciencedaily.com/releases/2018/07/180719094432.htm (Accessed 30 July 2018)