New research suggests that exercise — particularly moderate- to vigorous-intensity, such as brisk walking or jogging — may help to lower the risk of glaucoma, a leading cause of blindness.
The team — from the University of California, Los Angeles — behind the new study presented their new findings at the annual meeting of the American Academy of Ophthalmology, held in New Orleans, LA.
Using nationwide survey data collected in the United States, the researchers found that compared with the least active, the most physically active people appeared to have a 73 percent lower risk of developing glaucoma.
Around 3 million people in the U.S. have glaucoma, which is a range of diseases that damage the eye's optic nerve and cause vision loss. The most common form, open-angle glaucoma, increases pressure inside the eye.
There is no cure for glaucoma, but if it is caught early, there are treatments. These include prescription eye drops that can slow its progression and preserve vision.
Glaucoma is rising worldwide
Worldwide, glaucoma is the leading cause of irreversible blindness. Researchers have estimated that in 2013, worldwide, the number of people aged 40–80 with glaucoma was 64.3 million. This number is projected rise to 111.8 million by 2040.
Although glaucoma can affect anyone, there are certain groups with a higher risk of developing it. For example, in the U.S., it is more common in African Americans over the age of 40 and in all people aged 60 and over with a family history of the disease. It also more common in people with diabetes.
People can help to reduce vision loss from glaucoma by controlling their blood pressure, keeping to a healthy weight, and being physically active. These things also help to prevent diabetes and other conditions that are linked to higher risk of glaucoma.
There has been a long-held view that lifestyle choices do not influence glaucoma itself. But some recent studies have shown a link between lifestyle factors and eye pressure, which is a significant risk factor for glaucoma.
Tracking physical activity nationwide
Dr. Victoria L. Tseng, one of the researchers behind the new study, notes that some studies have shown that exercise can alter blood flow to the eye and the pressure inside it.
So, she and her colleagues decided to investigate the link between intensity of exercise and glaucoma, using data from the National Health and Nutrition Examination Survey (NHANES).
NHANES has been tracking health and nutrition in children and adults in the U.S. since the 1960s, and it is considered unique because participants undergo physical exams as well as interviews.
In 2003, the survey began to use wearable ActiGraph devices to monitor physical activity, such as walking and jogging. Before then, information on physical activity was collected in interviews.
Faster walking matched lower glaucoma risk
For the new study, the researchers used walking speed and steps per minute to define the level of physical activity. They note that 30 minutes of moderate to vigorous activity on at least 5 days of the week is equivalent to walking at least 7,000 steps per day, every day of the week.
When they analyzed the data, the team found a 6 percent reduction in the risk of developing glaucoma for every 10-unit increase in walking speed and steps per minute.
They also found a 25 percent reduction in risk of glaucoma for every 10-minute increase in the weekly amount of moderate to vigorous activity.
"Our research suggests that it is not only the act of exercising that may be associated with decreased glaucoma risk, but that people who exercise with higher speed and more steps of walking or running may even further decrease their glaucoma risk compared to people who exercise at lower speeds with less steps."
Dr. Victoria L. Tseng
However, the researchers point out that other teams now need to look more robustly at the direct relationship between glaucoma and physical activity before clinical guidelines on the findings can be formulated.
Dr. Tseng says that in the meantime, she will be advising her patients to exercise because it will benefit their overall health, as well as their eyes.