Longitudinal trajectories of sleep duration in the general population

Background Sleep duration has been associated with overall health status, health behaviours, and mortality. Little is known about habitual longitudinal patterns of sleep in the general population. Furthermore, evidence about whether sleep duration has declined in recent years is contradictory. Data and methods The study was based on 8,673 adults aged 18 or older in 2002/2003 (cycle 5 of the National Population Health Survey) and used fi ve selfreported biennial measurements of sleep duration spanning eight years. Multiple distinct trajectories of sleep duration were estimated using latent class growth modeling. Results Four modelled trajectories of sleep duration were identifi ed: short (11.1% of the population); low-normal (49.4%); high-normal (37.0%); and long (2.4%). The short, low-normal and highnormal sleep trajectories each exhibited a slight linear decline in hours of sleep over the eight years of follow-up. Poor sleep was predictive of trajectory group membership and associated with a decrease in sleep duration for three of the four groups. Age and sex were also significant predictors of trajectory group membership. Interpretation Trajectory analysis is a useful descriptive tool in the investigation of sleep duration over time.