Could Physical Activity Decrease Glaucoma Risk?
In the coming two years, experts believe an additional 80 million people will be diagnosed with glaucoma, a progressive disorder that affects the optic nerve and ultimately leads to blindness. Glaucoma causes the neuroretinal rim of the optic nerve to thin, while the optic nerve cup enlarges. As a result, the patient’s visual field grows smaller over time. Ophthalmologists have spent years trying to determine how this disease can be prevented. According to recent research in the journal Medicine and Science in Sports and Exercise, physical activity may help reduce the risk of glaucoma in older adults.
The Link between Physical Fitness and Glaucoma Risk
The researchers found that meeting the guidelines for physical activity and physical fitness could reduce the risk of developing glaucoma by up to 50 percent. The team looked at approximately 10,000 people in a long-term study and found that even people who exercised for fewer than the recommended 150 minutes per week experienced some risk reduction compared to people with sedentary lifestyles. This finding is important considering that physicians largely do not know how to prevent glaucoma, despite the fact that it is a leading cause of blindness and its prevalence is only set to increase in the years to come.
The mechanism through which physical activity reduces the risk of glaucoma is not entirely clear, but it is likely connected to intraocular pressure. The thinning of the optic nerve that occurs in glaucoma happens due to increased pressure in the inner eye. Prior research has shown physical activity lowers this pressure, in addition to the many other benefits it provides. Unfortunately, half of Americans do not currently meet the national guidelines of 150 minutes or more of moderate-intensity aerobic exercise, as well as two days of resistance training, each week. This fact could account in some part for the increasing rates of glaucoma.
The Study’s Surprising Findings about Fitness
In the study, researchers analyzed data on 9,519 men and women who were enrolled in the Aerobics Center Longitudinal Study and who received examinations at the Cooper Clinic in Dallas between 1987 and 2005. Participants ranged in age from 40 to 81. The study involved creating a record of weekly physical activity and measuring cardiovascular fitness with a treadmill test. Among these individuals, 128 new cases of glaucoma occurred during an average of about six years of follow-up.
In the end, people who met the physical activity guidelines were 50 percent less likely to develop glaucoma compared to people who logged no exercise time. Moreover, researchers noted lower risk among the fittest participants. People with the highest cardiovascular fitness levels (as demonstrated by treadmill tests) were 40 percent less likely to develop glaucoma compared to individuals with the lowest fitness levels.
The researchers in the study were surprised to find such a strong connection between physical activity, fitness and reduced glaucoma risk. In the end, they hypothesized that fitness may be one of the strongest factors in predicting glaucoma besides aging. At the same time, the study has limitations, since it was not designed to determine the direct influence of physical activity on glaucoma risk. In addition, participants self-reported their exercise, so there could be some false reporting.
However, it is clear that physical activity is beneficial on some level, so patients should be advised to keep as active as possible, especially those with a family history of glaucoma. While exercise does not take the place of regular eye screenings or medical treatments for glaucoma, it may help mitigate risk.
Another Key Study and a Possible Path Forward for Researchers
Physical activity may also help reduce the rate of visual field loss among patients who have already developed glaucoma. Another study, originally presented at the 2017 Association for Research in Vision and Ophthalmology Annual Meeting, looked at 141 patients with glaucoma between 60 and 80 years of age. Participants wore an accelerometer for one week to record general activity levels and minutes of non-sedentary activity. Throughout the study, researchers took measurements to record any loss of visual field in these patients.
On average, participants completed 5,613 steps per day and lost visual field sensitivity at a rate of 0.36 dB per year. However, each increase in 1,000 steps per day was associated with a smaller loss, and each 10-minute increase in vigorous or moderate exercise was associated with a slower yearly rate of visual field loss.
Visual field sensitivity declined more quickly in older participants and in those with a history of glaucoma or cataract surgery, as well as among people with worse baseline visual field loss. While the study has limitations, it points to the need for further exploration of how physical activity may slow vision loss in people with glaucoma.
The findings of these studies are still preliminary, but they point to some important research that should take place in the years to come. First, investigators need to develop a clearer understanding of exactly how physical activity can reduce the risk of glaucoma. Identifying this mechanism could point to future interventions, including better recommendations on how much exercise people should do and the type of activity that is most beneficial. Furthermore, researchers need to examine using physical exercise as a means of slowing the progression of glaucoma through clinical trials. The observational study mentioned above provides some justification for clinical trials to articulate the connection between visual field loss and activity.