People who exercised regularly early in the morning were significantly less likely to develop coronary artery disease, high blood pressure, type 2 diabetes, and obesity than those who exercised later in the day, according to a study presented at the American College of Cardiology’s Annual Scientific Meeting (ACC.26).
The study was based on more than 14,000 people’s health records and heart rate data from Fitbit. Although it is unclear whether the relationship between exercise timing and cardiometabolic health is causal or mediated by other factors, the researchers said their findings could inform approaches to counseling patients about physical activity based on a more detailed examination of exercise behavior than previously possible.
While any exercise is better than no exercise, we sought to identify additional aspects of exercise timing. Being able to exercise in the morning appears to be associated with a higher incidence of cardiometabolic disease. ”
Prem Patel, medical student at the University of Massachusetts Chan School of Medicine and lead author of the study
Cardiometabolic disease markers such as hypertension, diabetes, and obesity are associated with an increased risk of heart disease, the leading cause of death worldwide. Regular physical activity is known to reduce these markers and the risk of serious cardiac events.
Researchers analyzed data from 14,489 people participating in a large national survey, All of Us. Minute-by-minute heart rate data from Fitbit devices was analyzed over a one-year period. To track acute physical activity, researchers identified periods during which participants’ heart rates increased for 15 consecutive minutes or more. This methodology differs from other studies because it is based on the body’s response to exercise (increased heart rate), rather than tracking specific activities such as walking to work, doing housework, or training at the gym.
The researchers assessed each participant’s exercise at 15-minute intervals throughout the day and grouped participants into categories based on the timing of their exercise. Researchers analyzed the association between exercise timing and high blood pressure, diabetes, obesity, and hyperlipidemia (elevated LDL-C cholesterol or triglycerides) based on health records. We also assessed the incidence of cardiovascular diseases such as coronary artery disease and atrial fibrillation, and considered other risk factors associated with cardiovascular health, such as age, gender, income level, total activity level, sleep duration, alcohol intake, and smoking status.
Compared to people who exercised later in the day, people who exercised frequently in the morning were 31% less likely to have coronary artery disease, 18% less likely to have high blood pressure, 21% less likely to have hyperlipidemia, 30% less likely to have type 2 diabetes, and 35% less likely to be obese. These associations were independent of total daily physical activity. Exercise between 7 a.m. and 8 a.m. was associated with the lowest risk of coronary artery disease.
The researchers said this study provides a more comprehensive view of exercise than previous studies and suggests that the timing of exercise may represent a previously underappreciated aspect of cardiometabolic health. Most studies have historically assessed total physical activity levels or tracked exercise timing over short periods of time. This is the first large-scale study to assess exercise intensity and timing based on long-term data from wearable devices.
“Until now, researchers have primarily focused on how much physical activity one should do, the number of hours of physical activity, or the intensity,” Patel said. “One in three Americans now owns a wearable device that allows them to see their exercise down to a minute-by-minute level, opening many doors in terms of new analytics.”
The researchers said the study results only show an association, not whether early exercise habits cause improvements in health markers. Patel said biological factors such as hormones, sleep and genetics may play a role in the observed association. Behavioral and psychological factors may also be involved. For example, exercising earlier in the day may increase your energy levels throughout the day and allow you to make healthier food choices. Alternatively, exercise may be more common among people who generally prioritize healthy habits. Further research could help determine the role of such factors and inform exercise recommendations, the authors said.
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American College of Cardiology
