Consistency of sleep timing and duration are associated with more physical activity and favorable heart rate metrics in a naturalistic cohort

The study analyzed sleep, physical activity, and heart rate data from over 81,000 participants (more than 18 million nights) from the Apple Heart and Movement Study. Researchers measured sleep consistency using standard deviation of sleep duration, sleep start and end times, and the Sleep Regularity Index. Results showed that more consistent sleep was associated with higher physical activity (32.8 minutes of daily exercise in the most consistent sleep group versus 20.4 minutes in the least consistent group). People with consistent sleep had lower resting heart rate (62.4 versus 65.6 beats per minute) and higher heart rate variability (40.6 versus 37.3). All these differences were statistically highly significant. The study concluded that sleep consistency is associated with positive health indicators.