Seeing the light – how walking can help prevent sight loss
Published 20/03/2014 | 02:30
Here's one bit of walking-related health news I didn't expect to be sharing: walking can stop you going blind. Almost literally true and pretty exciting to anybody worried about sight loss – which includes most over-40s.
Research conducted by Dr Machelle Pardue and her colleagues at the Atlanta Centre for Visual and Neurocognitive Rehabilitation at Emory University, tested the effect of aerobic exercise on retinal cells undergoing degeneration.
The researchers claim the findings, which they report in The Journal of Neuroscience, point to moderate exercise as a possible treatment for slowing down eye diseases such as age-related macular degeneration (AMD), a leading cause of blindness in the elderly.
Macular degeneration is caused by the death of photoreceptors in the retina, the 'camera' at the back of the eye which turns light signals into nerve impulses. It is a condition that typically affects your eyes as you get older. In the over-50s, AMD is the leading cause of sight loss in Ireland, with more than 7,000 new cases every year. AMD affects the macula – a small part of the eye responsible for central vision which allows you to see detail. It usually starts in one eye and is highly likely to affect the other.
Dr Pardue's team studied mice that ran on a treadmill for two weeks before and after being exposed to bright light to trigger retinal cell loss and mimic the disease. They worked with two groups: an 'exercise' group and a 'non-exercise' group. The exercise group ran on treadmills for an hour a day, five days per week for two weeks, while the non-exercise group were placed on stationary treadmills during the same periods.
Exercised animals ended up with nearly twice as many photoreceptors as mice that spent the same amount of time on a stationary treadmill. Their retinal cells were also more responsive to light.
Although studies on both animal and human subjects have suggested exercise may slow down the progress of neurodegenerative diseases or injury, there is little information about how it might affect vision. It has been suggested that aerobic exercise works by stimulating a protein called brain-derived neurotrophic factor (BDNF), which helps brain cells grow and function properly. They also found that the 'exercised' mice had 20pc higher levels of BDNF protein than the non-exercised mice.
In order to confirm that it was BDNF that was channelling the effect of exercise, the researchers injected the mice with a drug that blocked the action of the protein and found that it reduced retinal function and photoreceptor counts in the exercised mice to 'inactive levels'. According to the researchers, the findings "suggest that aerobic exercise is neuroprotective for retinal degeneration and that this effect is mediated by BDNF signalling".
'This research may lead to tailored exercise regimens or combination therapies in treatments of retinal degenerative diseases," said Dr Pardue. "One point to emphasise is that the exercise the animals engaged in is really comparable to a brisk walk. A previous study that examined the effects of exercise on vision in humans had examined a select group of long-distance runners. Our results suggest it's possible to attain these effects with more moderate exercise."
Good news for mice and men.
Conor O'Hagan is editor of bimonthly Walking World Ireland mag: walkingworldireland.com
Walk of the Week: Wood Loop Ballyvaughan, Co Clare
Time: 2hrs-2hr 30mins
Terrain: Minor roadways, green lanes, woodland, cross-country
The trailhead is located in Ballyvaughan, at the car park on the coast road to Fanore. Follow the road for 300m past thatched cottages and across a bridge to reach a roadway on the left, signposted for Burren Way.
Turn left and follow the roadway past the school and on to a second Burren Way signpost. Veer right; follow the arrows across a series of stone stiles and wooded sections to exit into a field that takes you to a surfaced roadway where the Burren Way turns right – but you turn left.
Follow the roadway for 300m to reach the main N67 road where you turn left and, almost immediately, turn right again on to a minor road.
Follow this road to its conclusion at a metal gate into a field. Cross the stile and follow the purple arrows across the fields, stiles and sandy roadways to exit at the entrance to Aillwee Cave where you turn left.
Now follow the roadway for 2k to reach a Tjunction where you turn left, pass through a gateway and join a 'green' laneway.
Follow it for 300m to exit at a double gate.
Continue straight as the laneway changes to a surfaced roadway and eventually reaches a Tjunction where you turn left.
After 400m on this surfaced road you join the N67 Galway road where you turn left for the last 500m back to the trailhead