Sun Exposure and Myopia in Adult Australian Participants of the 45 and Up Study

Purpose: Sun exposure has important effects on human health, including risk of myopia (short-sightedness). We examined the association between outdoor time in the sun and myopia in 16,543 Australian-born adult participants of the 45 and Up study (aged 58–99 years). Methods: At the baseline survey (2005–2009), participants of the 45 and Up study self-reported history of skin cancer and outdoor, sun exposure and sedentary behaviours. At the Health Compass Survey follow-up (2022), participants additionally self-reported their history of myopia. Associations were analysed using multivariable logistic regression. Results: The prevalence of self-reported myopia was 53.1%, likely representing an over-estimate. Higher prevalence of self-reported myopia was associated with self-identifying as female (odds ratio [OR]=1.26, 95% confidence interval [CI]: 1.17, 1.35, p < 0.001), being younger (OR = 1.45, 95% CI: 1.19, 1.79, p < 0.001 for age 55–64 years vs age 85+ years), exercising less (OR = 1.04, 95% CI: 1.00, 1.09, p = 0.04), spending less time outdoors in the sun (OR = 1.05, 95% CI: 1.03, 1.08, p < 0.001) spending more time sitting (OR = 1.02, 95% CI: 1.01, 1.04, p < 0.001) and having lower propensity to tan (OR = 1.19, 95% CI: 1.06, 1.35, p = 0.005 for Never tan vs Get very tanned after sun exposure). Conclusions: In adulthood, higher time spent outdoors was associated with lower prevalence of self-reported myopia. This may indicate that outdoor behaviours in adulthood reflect those in childhood, when myopia develops. However, caution interpreting these findings is warranted due to the cross-sectional design, potential misclassification of myopia and temporal gap (13–17 years) between self-reporting of outdoor time and myopia status.