Myopia and skin cancer are inversely correlated: results of the Busselton Healthy Ageing Study

To the Editor: Myopia is a major public health problem, and is increasing in prevalence and severity.1 The complications of high myopia (defined as a spherical equivalent [SE] > 6.00 diopters [D] or axial length > 26.5 mm) can be sight-threatening.2

Spending more time outdoors is associated with less myopia and clinical trials currently underway in China are aimed at reducing the development and progression of myopia in schoolchildren through increased outdoor activity.3

In fair-skinned populations, increased time outdoors also increases the risk of developing skin cancers. Australia has among the highest skin cancer rates in the world.4

We tested the hypothesis that people who have developed ultraviolet (UV) radiation-related skin cancer as a result of excessive time spent outdoors are less myopic compared with age-matched people with no prior history of skin cancer. Our cohort included 1861 participants of the Busselton Healthy Ageing Study (BHAS), a cross-sectional survey of individuals born in 1946–1964 and living in a Western Australian rural coastal community.5 Participants completed a questionnaire including their previous medical history. Refractive error was measured by autorefraction using the Nidek ref/keratometer ARK-510A.

The cohort was of northern European ancestry, the mean age was 56.3 years (range, 45.5 to 66.4 years) and 986 (53.0%) were men. There were 143 participants (7.7%) with a previous history of either cutaneous melanoma, squamous cell carcinoma or basal cell carcinoma.

There was a significant difference in the prevalence of myopia between the skin cancer and control groups (χ2 test, P = 0.005) (Box). In a regression model adjusted for age, sex and education, the odds of being non-myopic were 2.3 times higher in the skin cancer group compared with controls (95% CI, 1.42–4.11; P = 0.002). For every 1.00 D increase in mean SE, the odds of having skin cancer increased by a factor of 1.18 (95% CI, 1.04–1.34; P = 0.01). The outcomes of the analysis were not significantly altered after removing participants with cataract.

This study highlights that while spending time outdoors lessens an individual's risk of developing myopia, recommendations to increase outdoor activity in childhood must also take into account the potentially harmful effects of exposure to UV radiation.