Those who are more prone to tanning from UV exposure had a lower cataract surgery risk in this study. Photo: Matheus Frade on Unsplash.

It’s long been known that prolonged outdoor time increases UV exposure and thus the incidence of cataract development. But an unusual new study links outdoor time with a lower incidence of cataract surgery in a large Australian cohort. The key difference seems to be the individual’s propensity to tanning and the role of melanin.

This population-based prospective cohort study included 137,133 participants 45 to 65 years old without prior history of cataract surgery. Time spent outside and tanning from repeated sun exposure were assessed through a baseline questionnaire. Whether a patient proceeded to need and receive cataract surgery was then determined.

During a mean follow-up of nine years, 10% of participants received cataract surgery.  More time outdoors and tanning from repeated sun exposure were significantly associated with a lower risk of cataract surgery. Participants who spent over 10 hours outside had a 9% decreased risk compared with those who spent fewer than two hours outside. Compared with participants who easily tanned from repeated sun exposure, those less likely to tan had a 5% to 7% increased risk.

“We found reduced risk of cataract surgery among participants who reported more outdoor time,” the study authors noted in their paper, and that “subjects who tan easily had lower risk, suggesting a potential role between melanin and cataract.” A suntan is a sign that the skin is releasing melanin, the paper explained, which is a natural protector against the UV rays of the sun. The team speculated that one explanation could be that “those who tan easily have higher melanin levels and better antioxidant capability and thus a lower risk of cataract.” Meanwhile, older study participants who tanned less were found to have increased cataract risk, which could be due to reduced melanin levels due to older age.

Han X, Zhang J, Wang W, et al. Associations among outdoor time, skin tanning, and the risk of surgically treated cataract for Australians 45 to 65 years of age. Transl Vis Sci Technol. June 2, 2022. [Epub ahead of print].