Exercise Reduces Risk of Developing Age-Related Cataracts

Regular physical exercise reduces the risk of developing age-related cataracts (ARC) by up to 10%, according to a dose-response meta-analysis published in the International Journal of Ophthalmology. ARC is one of the leading causes of vision impairment throughout the world and is estimated to account for 13.4 million cases of blindness.

Aging and oxidative damage are thought to contribute to ARC development; however, the exact underlying pathogenic mechanisms are not completely understood. “Cataract extraction surgery is effective in recovering vision,” authors write. But “the high therapeutic costs and increasing demands for therapy have conferred a considerable financial burden to healthcare organizations and society in general.” Identifying measures that can prevent or delay development of ARC can potentially lead to cost savings and improved visual outcomes.

Investigators searched online databases Pubmed, Embase, Web of Science, and Cochrane Library for relevant studies published through July 2019. In total, 6 prospective cohort studies involving 171,620 participants were included in the final review.

To calculate overall summary estimates, researchers determined multivariable-adjusted relative risks (RRs) and 95% confidence intervals (CIs). Of the 6 studies, average follow-up periods ranged from 6.2 to 12.1 years while 4 were conducted in the United States, 1 in Sweden, and one in the United Kingdom. All physical activity data were collected via questionnaires.

The analysis found:

• Increased physical activity was significantly associated with reduced risk of ARC by 10% (RR: 0.90; 95% CI, 0.81-0.99; P = .04)
• Analysis by assessment method for physical activity suggested studies using metabolic equivalent (MET) per day reported slightly stronger associations with ARC (RR: 0.85; 95% CI, 0.81-0.90; P <.001) than studies which assessed activity by weekly activity (RR: 0.96; 95%CI, 0.89-1.03; P = .24)
• Risk of ARC decreased by 2% (RR: 0.98; 95% CI, 0.98-0.99; P <.001) for every 6 METs (roughly equivalent to jogging or cycling for 1 hour) per day increase in activity

One reason exercise may reduce risk of ARC is due to the fact physical activity reduces oxidative stress in the eye, inhibiting lipid degradation which can cause cell damage. Long-term physical activity elevates high-density lipoprotein (HDL), which may carry more antioxidants to the lens from plasma, preventing oxidative damage. Insulin resistance and lipid profiles, both associated with increased risk of ARC, can also be improved through exercise.

“We know that exercise increases antioxidant enzyme activity which has all sorts of benefits, including limiting infections and inflammation in the eye,” said study author Ming Li, PhD, in a statement. She continued, “The lens is highly susceptible to oxidative damage because of its high concentration of polyunsaturated fatty acid and its specific biological function.”

One limitation to the study is that lens opacities can progress in the absence of obvious symptoms, meaning self-reported cases of ARC may underestimate actual prevalence. Researchers also caution against generalizing results to other racial and ethnic groups as data in the analysis came from largely western populations.

Authors conclude the findings support current guidelines advocating for inclusion of physical activity as part of a healthy lifestyle to help prevent or delay onset of age-related diseases.

Reference:

Jiang H, Wang L, Liu Y, et al. Physical activity and risk of age-related cataract. Int J Ophthalmol. 2020;13(4):643-649. doi: 10.18240/ijo.2020.04.18.