by Helen Carter, Journalist, Optometry Australia 2020
Another great reason to keep up physical exercise has now been added to the list. Several studies have provided evidence that regular physical exercise reduces the risk of age-related cataracts.
Australian and Chinese researchers analysed data from six different studies of more than 171,000 people looking at how exercise reduces oxidative damage in the eye. The studies included 19,173 cases of cataract. Participants from America, the UK and Sweden were followed for six to 12 years.
The research found that exercise appears helpful in cataract prevention, as well as being beneficial for other eye conditions including possibly reducing risks of developing glaucoma and age-related macular degeneration (AMD), plus delaying progression of AMD and diabetic retinopathy.
Researchers found a 10 per cent reduction in age-related cataracts among people who engaged in regular physical activity such as walking and cycling. And they said the risk of developing cataracts could potentially decrease by two per cent for every hour of cycling or jogging.
The researchers from the University of South Australia and Xi’an Jiatong University, China, published their findings in the International Journal of Ophthalmology.
Reduces oxidative stress
The researchers said physical activity could reduce levels of oxidative stress (the primary cause of cataracts from natural aging) by increasing the activity of antioxidant enzymes.
Co-author of the research, Dr Ming Li, said physical activity reduces oxidative stress in the eye by inhibiting lipid degradation which results in cell damage.
"We know that exercise increases antioxidant enzyme activity which has all sorts of benefits, including limiting infections and inflammation in the eye," Dr Li said.
Previous studies showed that long-term physical activity elevates HDL (high-density lipoprotein) or ‘good cholesterol’, which may carry more antioxidants from plasma to the lens to prevent oxidative damage.
Exercise also improves insulin resistance and lipid profiles, which have been associated with an increased risk of age-related cataract.
"Age-related cataracts are one of the most common causes of vision impairment and blindness in the world and although surgery is an effective option to recover vision, it is very costly," Dr Li said.
"Considering the fact that 24 per cent of adults are inactive, these findings will hopefully encourage older people to start exercising on a regular basis."
Exercise and other eye conditions
The Macular Disease Foundation Australia says there is evidence that people with AMD who exercise regularly are less likely to progress to late-stage disease, while other research suggests vigorous exercise such as running reduces the risk of developing AMD.
The MD foundation says people with diabetic retinopathy can also experience vision protecting effects from exercise.
"Strict control of blood glucose levels will significantly reduce the long-term risk of vision loss,’ the foundation says. "Diet and exercise, along with prescribed medications, are key to achieving control of blood glucose."
Glaucoma Australia says research shows that people who engage in moderate to vigorous physical activity may be able to significantly lower their risk of glaucoma. The US study which followed 70 million adults since the 1960s found that for each 10-minute increase in moderate-to-vigorous activity per week, glaucoma risk decreased 25 per cent.
In Australia over 700,000 people are living with cataracts, with cataract surgery the most commonly performed eye procedure nationally. Sun (UV) exposure, smoking and diabetes can also contribute to cataract formation.
Over a 10-year period in those aged 49 and over, the risk of developing nuclear cataracts is 36 per cent and 28 per cent for cortical cataracts. In Australia, of those who do develop cataracts, the average age for cataract surgery is 75.8 years.
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