Physical Activity May Reduce Cataract Risk

March 20, 2015

High levels of total and long-term physical activity, as well as specific types of physical activity, may decrease the risk for age-related cataract later in life, researchers report in an article published in the February issue of Ophthalmology.

Of 52,660 men and women 45 to 83 years of age who completed questionnaires to assess physical activity as part of two large population-based cohorts, 11,580 developed age-related cataract during a 12-year follow-up period, write Jinjin Zheng Selin, MSc, from the Division of Nutritional Epidemiology, Institute of Environmental Medicine, Karolinska Institutet, Stockholm, Sweden, and colleagues.

Participants with the highest quartile of physical activity had a 13% decreased risk of developing cataracts relative to those with the lowest levels of physical activity, after adjustments for multiple factors including fruit and vegetable intake, antioxidant supplement use, and alcohol intake (hazard ratio [HR], 0.87; 95% confidence interval [CI], 0.83 - 0.92).

In addition, increased amounts of long-term total physical activity both at 30 years of age and at the beginning of the study (mean age, 59.4 years) decreased the risk for cataract by 24% compared with low levels of activity, according to the researchers (HR, 0.76; 95% CI, 0.69 - 0.85).

Participants answered six questions about physical activity and inactivity habits during the previous year at baseline. The specific types and time spent on different physical activities included walking or bicycling (hardly ever to more than 1.5 hours daily), leisure time exercise (less than 1 hour to more than 5 hours weekly), work or occupational activity (mostly sitting to heavy manual labor), home or housework (less than 1 hour to more than 8 hours daily), and inactive leisure time (less than 1 hour to more than 6 hours daily).

When the investigators looked at specific activities, they found that walking or bicycling 60 minutes per day or more decreased the risk for cataract by 12% compared with hardly ever walking or bicycling, and work or occupational activity requiring heavy manual labor decreased the risk for cataract by 16% compared with mostly sedentary occupations. Compared with individuals reporting less than 1 hour of leisure time inactivity per day, those who were physically inactive for 6 or more hours of leisure time daily were 27% more likely to develop age-related cataract, they write.

"Our results on different types of physical activity suggest that being physically active on a regular daily basis may contribute to decreased risk of cataract, rather than short weekly episodes of exercising/training," Selin explained in an interview with Medscape Medical News.

No association was observed between home or housework and risk for cataract. "This may be due to different types of tasks and activity levels performed," Selin said.

There may be several possible mechanisms behind the inverse association between high levels of physical activity and cataract risk, including lower levels of oxidative stress and inflammation and improved insulin resistance and lipid profiles, according to Selin. "Physical activity may also be related to a healthy lifestyle," he said.

"Because this is an observational study, we cannot rule out the possibility of unmeasured or residual confounding. However, we have adjusted for several potential confounders in the analyses, and the results remained similar," Selin explained.

The new findings are consistent with previous data, according to Manuel B. Datiles III, MD, medical officer and senior investigator and senior attending Ophthalmologist from the National Institutes of Health National Eye Institute in Bethesda, Maryland.

"In one of the previous papers, published in 2009, the author contends that when one is well conditioned, there is good evidence that one's defense against oxidative stress is also high, and this helps prevent cataract formation," Dr Datiles explained to Medscape Medical News. "Oxidative stress is one of the main causes of cataract, and antioxidants help lower one's risk for cataract."

In addition, according to Dr Datiles, who was not involved in the current investigation, "there are many papers that deal with obesity — indirectly reflecting on lack of physical activity — and higher risk of cataracts. And researchers have also studied body mass index and correlated it with cataract risk, again a reflection of lack of physical activity."

The current study extends the earlier data by prospectively examining the association of total and specific types of physical activity, as well as inactivity, with the risk for age-related cataract in a general population, Dr Datiles explained.

At this time, surgical extraction is the only treatment for cataract. For this reason, "it is of particular importance to identify protective factors as well as risk factors for cataract," the authors write.

The study was supported by research grants from the Swedish Research council for Health, Working Life and Welfare and the Swedish Research Council/Committee for Infrastructure, Stockholm.The authors and Dr Datiles have disclosed no relevant financial relationships.

Ophthalmology. 2015;122:274-280. Abstract


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