Older adults with higher physical activity levels as measured by accelerometer are at lower risk of developing atrial fibrillation, an analysis of UK Biobank data suggests. Researchers examined data on 93,669 participants in the UK Biobank study with a mean age of 62 (± 8 years) and no atrial fibrillation diagnosis who wore accelerometers on their wrists for one week to monitor activity. Over a median follow-up period of 5.2 years, there were 2,338 incident atrial fibrillation cases. Overall, 43,818 participants (46.8%) had at least 150 minutes per week of moderate to vigorous physical activity recorded by accelerometer, meeting minimum physical activity guidelines from the World Health Organization (WHO), the European Society of Cardiology, the American Heart Association, and other groups. A subset of 17,547 people (18.7%) got at least 300 minutes per week of moderate to vigorous physical activity, meeting an extended recommendation from the WHO for added health benefits. Compared to participants who didn't meet minimum exercise guidelines based on accelerometer data, those who did were significantly less likely to experience incident atrial fibrillation (hazard ratio 0.82) and stroke (HR 0.76). However, there was no association between self-reported physical activity and incident atrial fibrillation or stroke, and self-reported activity was only weakly correlated with accelerometer-derived activity levels. "Wearable devices that many of our patients now purchase are collecting important information that may enable inferences about lifestyle and disease risk," said senior study author Dr. Steven Lubitz, an associate professor at Harvard Medical School and a cardiac electrophysiologist at Massachusetts General Hospital in Boston. "Physical activity may become an important long-term ambulatory vital sign in the future, and it is highly likely that we will continue to see data from wearable devices interface with day to day clinical practice," Dr. Lubitz said by email. Interestingly, there was no statistically significant association between meeting the extended WHO activity guidelines of at least 300 minutes a week based on accelerometer data and incident atrial fibrillation. While there was a link between the extended WHO guidelines and stroke (HR 0.76), this benefit appeared similar to what researchers found for meeting the standard 150 minute per week guideline. One limitation of the study is that awareness of the accelerometer may have influenced participants' activity levels, the study team notes in the European Heart Journal. It's also possible that the single week of accelerometer-derived activity data wasn't representative of how much exercise participants got over time. "While wearing the device for a short period of time may have altered participant behavior, I don't believe the transient altered behavior would have had a meaningful impact on the future development of atrial fibrillation," said Dr. Saman Nazarian, an associate professor of cardiac electrophysiology at the University of Pennsylvania Perelman School of Medicine in Philadelphia. Patients who had higher levels of physical activity may also be different compared to those with lower levels of physical activity in many unmeasurable ways, Dr. Nazarian said. "For instance, they may be more motivated to seek medical attention and manage mediating factors, come from better socioeconomic backgrounds, and more likely to have arthritis, less likely to have asthma, less likely to be depressed, more likely to eat vegetables, less likely to drink, smoke, etc.," Dr. Nazarian, who wasn't involved in the study, said by email. "The only way to know, is to randomize patients to different levels of physical activity, and observe them for long enough regarding the incidence of atrial fibrillation," Dr. Nazarian said. —Lisa Rapaport Source
