An irregular heartbeat can affect more than your heart.

Atrial fibrillation — the most common type of irregular heartbeat — also accelerates age-related declines in walking speed, strength, balance and other aspects of physical performance, according to new research in the American Heart Association journal Circulation: Arrhythmia and Electrophysiology.

“Particularly in older adults, we need to be mindful that the effects of atrial fibrillation go beyond increasing the risk of heart failure and stroke,” said Jared W. Magnani, M.D., Ms.C., lead author of the study and assistant professor of medicine at Boston University in Massachusetts.

In atrial fibrillation, the heart’s two small upper chambers (atria) beat irregularly and too fast, which may increase the risk of stroke, heart failure and other conditions. The risk rises with age.

The researchers examined physical performance at ages 70, 74, 78 and 82 in 2,753 participants in the Health, Aging and Body Composition, a long-term study of aging-related health outcomes in Medicare recipients.

Comparing four-year changes in physical performance between participants recently diagnosed with AFib and those without, researchers found:

Participants’ physical performance declined with age, as expected.

Participants diagnosed with AFib had a significantly greater and swifter decline in physical performance tests of balance, grip strength and how far a person could walk in two minutes.

Participants with AFib completed a 400-meter walk (one lap around a standard track) an average 20 seconds slower than those without AFib.

The excess decline in physical performance in people with AFib was equivalent to an extra four years of aging.

“Small declines in physical performance in older adults may have big consequences,” Magnani said. “The declines that we observed in participants with AFib are associated with increased frailty, which can result in loss of independence, decreased mobility, poorer quality of life, institutionalization and death.”

Because the study only included people living independently, the results may not apply to older adults with greater cognitive or physical limitations.

The results also don’t prove a direct cause-and-effect link between AFib and declining physical performance, Magnani said. “There may be other factors, such as inflammation or accelerated muscle loss, that contribute to increased risk of AFib and declining physical performance.”