In this latest video from MedCram, Dr. Seheult reviews the effect of sunlight and melanoma.
Is sunlight a mixed bag?
Sunlight often gets a bad rap, mainly because of its connection to skin cancer. But a recent preprint study led by dermatologist Richard Weller from the University of Edinburgh challenges some of our assumptions about UV exposure and overall health. Using a large UK cohort of 419,000 adults followed over 15 years, this study examined the consequences of avoiding versus embracing sunlight, revealing some fascinating—and sometimes counterintuitive—results.
The study categorized participants using a scoring system called “Sunbeam,” which considered four aspects of UV exposure: time spent outdoors, residential UV light levels, solarium or sunlamp use, and habits around sun protection. Each participant was assigned points based on these factors, and their scores were grouped into low, medium, or high UV exposure. The researchers then tracked mortality and disease incidence over 15 years, accounting for confounding factors.
The results are striking. Participants with medium or high UV exposure had notable reductions in all-cause mortality. Specifically, a medium UV exposure score was associated with an 11 percent reduction in all-cause mortality compared to low UV, while a high score corresponded to a 16 percent reduction. Cardiovascular mortality showed an even more pronounced trend, with 18 percent and 23 percent reductions for medium and high UV exposure, respectively. Non-skin cancer mortality also trended lower among those with higher UV exposure.
When it comes to skin cancer, the findings are more nuanced. Melanoma mortality showed a slight increase at medium UV exposure, but the results were not statistically significant. For other skin cancers such as basal cell or squamous cell carcinomas, there was a statistically significant increase in incidence at medium and high UV levels, though these types of skin cancers are generally less lethal and often treatable.
Perhaps the most compelling part of this study is the population-level analysis. If everyone in the cohort avoided sunlight entirely, the study estimates that only 39 melanoma deaths would be prevented over 15 years. In contrast, this avoidance could result in nearly 3,000 additional deaths from other causes, including cardiovascular disease and other cancers. Conversely, if everyone had high UV exposure, there would be approximately 4,736 fewer all-cause deaths, with only 23 additional melanoma deaths and 12 extra cases of other skin cancers. These findings suggest that the benefits of sunlight, particularly for cardiovascular health and overall longevity, may outweigh the risks associated with skin cancer in midlife adults.
Timing and pattern of sun exposure also matter. Early-life intermittent sunburns are known to increase melanoma risk, but habitual midlife exposure, as captured in this study, appears much less harmful. Beyond vitamin D, sunlight delivers infrared light, which penetrates the body and may affect a wide range of cellular functions. The study also examined biomarkers such as IL22, suggesting that sunlight may support health in ways we are only beginning to understand.
In conclusion, this research underscores a critical point: while UV exposure does carry some risks, particularly for the skin, complete avoidance of sunlight may come with a steep cost for overall health. Moderate, habitual sun exposure in adulthood appears to reduce mortality from cardiovascular disease and certain cancers, and the risk of fatal melanoma remains relatively small. For those seeking to optimize health, this study provides compelling evidence that sunlight, when approached sensibly, may be an essential component of a long and healthy life.
For a deeper dive into this study and additional continuing medical education videos on sunlight and health, visit MedCram.
LINKS / REFERENCES:
Risk–benefit balance of habitual ultraviolet exposure for cardiovascular, cancer, and skin
cancer mortality: UK Biobank cohort study (medRxiv) | https://www.medrxiv.org/content/10.64…