Seasonal and geographic variation in sleep duration among U.S. adults: Evidence from the 2022 BRFSS

Sleep duration is a critical determinant of health that reflects the influence of biological, social, and environmental factors. Although geographic clustering of insufficient sleep in the United States has been described, seasonal and time-zone - related variation are less well understood. We analyzed the 2022 Behavioral Risk Factor Surveillance System (BRFSS) data from 416 731 adults, representing a weighted population of approximately 259 million. Using complex survey weights and general linear models adjusted for age and sex, we examined differences in self-reported sleep duration across months, time zones, and latitude bands. The overall mean sleep duration was 7.96 h. Monthly variation was modest and largely not statistically significant, with averages ranging from 7.82 hours in April to 8.13 h in January. In contrast, clear geographic differences emerged. Sleep duration varied significantly by time zone, with Pacific respondents reporting the longest sleep (8.37-8.56 h) and those in the Mountain and Hawaii time zones reporting the shortest (approximately 7.0-7.5 h). Adults in southern states reported consistently longer sleep than those in northern states, though the month × latitude interaction was not significant. Effect sizes were small across all models (ηp² range = 0.00002-0.00080; Cohen's <i>d</i> for latitude = 0.23), indicating modest but consistent geographic differences. Men slept less than women, and older adults reported slightly longer sleep. These findings suggest that geographic context, particularly time zone and latitude, plays a more consistent role than seasonality in shaping sleep duration in the U.S.