Tracking the Night: Measuring Age and Sex Patterns in Sleep Duration Using Wearable Technology

STUDY OBJECTIVES: Sleep duration is a key component of overall sleep health, but prior population-level studies characterizing this have relied on brief self-report questions (often one item) or used different objective devices within the same study. We examined the normal variation of sleep duration in an adult population using a single consumer-grade wearable device with a unified algorithm. METHODS: Retrospective cohort study conducted in the United States. Data were analyzed from 274,128 U.S.-based adults aged 20 to 69 who used a Samsung Galaxy Watch between February 2023 and April 2023; participants were included if they had ≥20 valid weekdays and ≥8 valid weekend days of data. Sleep duration was the primary outcome, defined as the longest continuous nighttime sleep period between 6:00 p.m. and 6:00 a.m. averaged over a three-month period. Sleep duration and weekday-weekend variability were examined across age groups and by sex using descriptive statistics and independent t-tests. RESULTS: Overall, average sleep duration was 7.57 hours, with a 10th-90th percentile range of 6.5 to 8.9 hours. Sleep duration was shortest in the 40-49 year old group (7.54 hours) and longest in the 60-69 year old group (7.75 hours; p < .001). Overall, 23.0% of adults slept less than 7 hours, more commonly among those aged 40-49 (25.1%) and 50-59 (24.7%). Across all age groups, weekend sleep was longer than weekday sleep by an average of 28 minutes, with the largest gap in the 40-49 year old group (34 minutes), and the smallest in the 60-69 year old group (20 minutes). Women consistently slept longer than men (+18 minutes on average), and exhibited greater between-subject variability in total sleep duration (SD = 1.61 hours for women vs. 1.54 hours for men). CONCLUSIONS: This study demonstrates considerable variability in objectively measured sleep duration across adulthood, spanning a broad range and differing by age groups and sex. These findings provide reference distributions that may inform clinical expectations and public health messaging regarding sleep duration.