Epidemiology of the human circadian clock.
Level 4 - case-series / case-control
Cross-sectional epidemiological survey by design analogy
PubMed 17936039 · doi:10.1016/j.smrv.2007.07.005
What was done
Authors developed and evaluated the Munich ChronoType Questionnaire (MCTQ) to assess human chronotypes and sleep-wake timing across work and free days. More than 55,000 participants completed the questionnaire, which was validated against the Horne-Östberg Morningness-Eveningness Questionnaire, sleep logs, actimetry, and physiological parameters.
What was found
Sleep and wake times showed a near-Gaussian distribution across the population. Sleep timing and duration were generally independent, but sleep duration strongly depended on chronotype when work and free days were analyzed separately. Chronotype was also age- and sex-dependent. The abstract reports no numerical values or effect sizes.
Why it matters
This work established a validated tool to measure human circadian timing at population scale, showing how work schedules differentially affect sleep duration across distinct chronotypes.
Limits
The abstract reports no numerical estimates, standard deviations, or statistical tests. The underlying dataset relies primarily on self-reported survey responses, and detailed population demographics are not reported in the abstract.
Cited by
- supports The majority of the human population has an intermediate chronotype, naturally preferring to wake up between 6:00 a.m. and 8:00 a.m. and go to sleep between 10:00 p.m. and midnight.