ACC study links 7–8 a.m. workouts

The American College of Cardiology said on March 18 that a study of 14,489 adults found exercise between 7 a.m. and 8 a.m. was associated with the lowest odds of several cardiometabolic conditions. The research used Fitbit-derived heart-rate data and electronic health records from participants in the National Institutes of Health’s All of Us program, according to the ACC press release. The findings were presented ahead of ACC.26, the group’s annual scientific meeting in New Orleans from March 28 to March 30. The study was observational, and the researchers said it did not show that morning exercise directly caused lower risk. ### Where did the 7-to-8 a.m. claim come from? ACC said researchers analyzed one year of activity data from 14,489 people and sorted exercise into 15-minute intervals across the day. They then grouped participants by when they were most active and compared those patterns with diagnoses and risk markers in health records. (acc.org) The 7 a.m. to 8 a.m. window was associated with the lowest odds of coronary artery disease, according to the ACC summary. Coverage citing the same research said the morning pattern also tracked with lower odds of Type 2 diabetes and obesity compared with later-day exercise. ### What conditions were included in the analysis? (acc.org) Researchers examined associations with high blood pressure, diabetes, obesity and hyperlipidemia, the ACC release said. The cardiology group described those conditions as cardiometabolic disease markers tied to higher heart-disease risk. US Magazine’s June 1 summary of the study said morning exercisers were 31% less likely to have coronary artery disease, 30% less likely to have Type 2 diabetes and 35% less likely to have obesity. (acc.org) That report said the associations remained after accounting for total daily activity. ### How was “exercise” measured in the study? (acc.org) Yahoo Health said researchers tracked elevated heart rate lasting at least 15 consecutive minutes using Fitbit data from adults enrolled in All of Us. That approach let the team compare timing patterns across a large sample rather than rely only on self-reported workout habits. ACC said the study combined those wearable-derived activity patterns with health-record data. (usmagazine.com) The organization said the work offered what researchers called a more granular view of exercise timing and cardiometabolic health than earlier studies. ### Did the researchers say morning workouts are definitively better? (health.yahoo.com) Lead author Prem Patel, a medical student at the University of Massachusetts Chan Medical School, said the relationship was not clearly causal. “Any exercise is going to be better than no exercise,” Patel said in the ACC release, adding that the team was trying to identify whether timing might be another dimension of physical activity. (acc.org) The ACC release said it remains unclear whether the association is causal or instead reflects other factors tied to people who exercise early. That means the findings point to a link, not a rule that later workouts are ineffective. ### Why are headlines saying 15,000 people if ACC says 14,489? ACC gave the exact sample size as 14,489 participants in its March 18 release. (acc.org) Consumer coverage published on June 1 and June 2 rounded that figure to “nearly 15,000” or “15,000 people.” The research was presented at ACC.26 in New Orleans from March 28 to March 30, according to the American College of Cardiology. (acc.org) The ACC release identifies Patel as lead author and says the data came from the NIH’s All of Us research program.