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

Abstract 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.