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What is already known on this subject?
What does this study add?

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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 five self-reported biennial measurements of sleep duration spanning eight years. Multiple distinct trajectories of sleep duration were estimated using latent class growth modeling.


Four modelled trajectories of sleep duration were identified: short (11.1% of the population); low-normal (49.4%); high-normal (37.0%); and long (2.4%). The short, low-normal and high-normal sleep trajectories each exhibited a slight linear decline in hours of sleep over the eight years of follow-up. Poor sleep quality 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.


Trajectory analysis is a useful descriptive tool in the investigation of sleep duration over time.


Latent class growth modelling, longitudinal studies, PROC TRAJ, sleep deprivation


Problems sleeping are relatively common—in 2002, for example, about 13% of Canadians aged 15 or older reported trouble falling or staying asleep. In the future, sleep problems may become even more prevalent because of the growing share of elderly people in the population and increases in the prevalence of obesity and other physical and psychiatric co-morbidities associated with sleep disturbances. [Full Text]


Heather Gilmour (1-613-951-2114; heather.gilmour@statcan.gc.ca) and Julie Bernier (1-613-951-4556; julie.bernier@statcan.gc.ca) are with the Health Analysis Division at Statistics Canada, Ottawa, Ontario, K1A 0T6. Mark Kaplan and Nathalie Huguet are with Portland State University, Portland, Oregon. Bentson McFarland is with Oregon Health and Science University. Saverio Stranges is with the University of Warwick Medical School, Coventry, UK. David Feeny is with the University of Alberta, Edmonton, Alberta.

What is already known on this subject?

  • Evidence indicates that sleep duration is associated with general health status, health behaviours and mortality.
  • People sleeping fewer than 6 or more than 9 hours are at the greatest risk of negative health outcomes.
  • Most information about the population prevalence of sleep duration is based on cross-sectional data.
  • Whether sleep duration has declined in recent years is unclear.

What does this study add?

  • Four sleep duration trajectories were identified in the Canadian adult population—short, low-normal, high-normal and long sleepers.
  • The percentage of the population who are habitual short or long sleepers is lower than the percentages estimated to be in these sleep categories at any one point in time.
  • A small, but statistically significant, downturn in sleep duration was evident in three of the four trajectory groups.
  • Age, sex and poor sleep quality were significantly associated with sleep duration.
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