49 Circadian Rhythm Statistics

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These circadian rhythm figures cover the measurement periods and populations identified in the available source material. Estimates, surveys and forecasts retain their reported scope.

Key Circadian Rhythm Statistics

The main findings are:

  • In a nationally representative NHANES worker sample, 37.6% reported short sleep (<7 hours), representing an estimated 54.1 million U.S. workers (NHANES study reported 2016; U.S. workers aged 18+).
  • Short sleep prevalence was 26.5% at ages 18–29, 31.6% at ages 30–44, 31.8% at ages 45–64 and 21.7% at age 65+ (2010; U.S. civilian employed adults).
  • Delayed sleep phase disorder was estimated at 0.17% prevalence in the general population (reviewed estimates).
  • A controlled light study enrolled 39 healthy young adults, including 16 women, with mean age 22.18±3.62 years (9-day inpatient experiment).
  • The NHANES rest-activity study analyzed 7,539 adults from the 2011–2014 waves (U.S. adults).
  • In postmortem human prefrontal cortex from 146 individuals, about 10% of detected transcripts showed significant circadian rhythmicity (human postmortem study).
  • Short sleep was reported by 61.8% of night-shift workers versus 35.9% of daytime workers in the NHANES analysis (NHANES study reported 2016; U.S. workers).
  • Among night-shift workers, short sleep prevalence was 37.4% at ages 18–29, 51.1% at ages 30–44 and 46.4% at ages 45–64 (2010; U.S. night-shift workers).
  • Delayed sleep phase disorder was estimated in 7%–16% of adolescents (reviewed estimates).
  • A 0.2-hour bright-light exposure produced a 1.07±0.36-hour phase delay in the reported comparison (controlled experiment; healthy young adults).
  • A one-quantile increase in relative amplitude was associated with a 0.54–0.57-year lower biological-age measure across KDM and PhenoAge models (NHANES 2011–2014; U.S. adults).
  • A meta-analysis across two prefrontal-cortex areas identified 235 genes with significant circadian expression rhythms (human postmortem study; human prefrontal cortex).
  • Prolonged sleep-onset latency affected 46.2% of night-shift workers, 43.0% of evening-shift workers, 42.1% of rotating-shift workers and 31.0% of daytime workers (NHANES study reported 2016; U.S. workers).
  • Short sleep prevalence was 29.8% among male workers and 30.3% among female workers across all shifts (2010; U.S. civilian employed adults).
  • An estimated 5%–10% of chronic insomnia patients in sleep clinics have delayed sleep phase disorder (reviewed estimates; chronic-insomnia sleep-clinic patients).

Contents

Circadian rhythm statistics in U.S. workers and shift schedules

  • In a nationally representative NHANES worker sample, 37.6% reported short sleep (<7 hours), representing an estimated 54.1 million U.S. workers (NHANES study reported 2016; U.S. workers aged 18+). (Shift Work and Sleep)
  • Short sleep was reported by 61.8% of night-shift workers versus 35.9% of daytime workers in the NHANES analysis (NHANES study reported 2016; U.S. workers). (Shift Work and Sleep)
  • Prolonged sleep-onset latency affected 46.2% of night-shift workers, 43.0% of evening-shift workers, 42.1% of rotating-shift workers and 31.0% of daytime workers (NHANES study reported 2016; U.S. workers). (Shift Work and Sleep)
  • Poor sleep quality was reported by 30.7% of night-shift workers (NHANES study reported 2016; U.S. night-shift workers). (Shift Work and Sleep)
  • Difficulty falling asleep was reported by 21.7% of night-shift workers and 21.2% of evening-shift workers, versus 12.7% of daytime workers (NHANES study reported 2016; U.S. workers). (Shift Work and Sleep)
  • Excessive daytime sleepiness was reported by 22.3% of night-shift workers versus 16.2% of daytime workers (NHANES study reported 2016; U.S. workers). (Shift Work and Sleep)
  • Insomnia, defined in the study as poor sleep quality plus impaired sleep-related activities of daily living, affected 18.5% of night-shift workers versus 8.4% of daytime workers (NHANES study reported 2016; U.S. workers). (Shift Work and Sleep)
  • Among employed U.S. adults in NHIS 2010, 30.0% reported average sleep of 6 hours or less, about 40.6 million workers (U.S. civilian employed adults). (Short Sleep Duration Among Workers…)
  • NHIS 2010 short sleep prevalence was 44.0% on regular night shifts, 28.8% on regular day shifts and 31.6% on other shifts (U.S. civilian employed adults). (Short Sleep Duration Among Workers…)
  • In NHIS 2010, 72.6% of workers reported regular daytime shifts, 3.7% regular night shifts and 23.5% another shift category (U.S. civilian employed adults). (Short Sleep Duration Among Workers…)
  • The estimated number with short sleep was about 2.2 million among night-shift workers versus 28.3 million among day-shift workers (2010; U.S. civilian employed adults). (Short Sleep Duration Among Workers…)

Self-reported survey estimate; short sleep defined as <7 hours in this study.

Cross-sectional, self-reported and adjusted observational comparisons.

Latency means at least 30 minutes to fall asleep; survey measure.

Self-reported quality, not a clinical circadian diagnosis.

Observational self-report.

Self-reported symptom.

Study-specific operational definition; not a clinical diagnosis.

Whole-hour self-report; ≤6-hour definition differs from s1.

Other shifts combine evening, rotating and other schedules.

Usual shift self-report; categories do not measure circadian phase directly.

Weighted survey estimates; larger day-shift population produces the larger count.

Short sleep and circadian disruption by age, sex, race and work pattern

  • Short sleep prevalence was 26.5% at ages 18–29, 31.6% at ages 30–44, 31.8% at ages 45–64 and 21.7% at age 65+ (2010; U.S. civilian employed adults). (Short Sleep Duration Among Workers…)
  • Among night-shift workers, short sleep prevalence was 37.4% at ages 18–29, 51.1% at ages 30–44 and 46.4% at ages 45–64 (2010; U.S. night-shift workers). (Short Sleep Duration Among Workers…)
  • Short sleep prevalence was 29.8% among male workers and 30.3% among female workers across all shifts (2010; U.S. civilian employed adults). (Short Sleep Duration Among Workers…)
  • Among night-shift workers, short sleep prevalence was 41.7% for men and 46.6% for women (2010; U.S. night-shift workers). (Short Sleep Duration Among Workers…)
  • Across shifts, short sleep prevalence was 28.6% among non-Hispanic White workers, 38.9% among non-Hispanic Black workers, 33.2% among non-Hispanic Asian workers, 35.3% among other non-Hispanic workers and 28.8% among Hispanic workers (2010; U.S. civilian employed adults). (Short Sleep Duration Among Workers…)
  • Short sleep prevalence was 36.4% among widowed, divorced or separated workers, 29.4% among currently married workers and 28.2% among never-married workers (2010; U.S. civilian employed adults). (Short Sleep Duration Among Workers…)
  • Short sleep prevalence was 33.7% among workers with a high-school diploma, 33.8% with some college, 29.1% with less education and 26.7% with more education (2010; U.S. civilian employed adults). (Short Sleep Duration Among Workers…)
  • Workers with more than one job reported short sleep at 37.0%, compared with 29.4% for workers with one job (2010; U.S. civilian employed adults). (Short Sleep Duration Among Workers…)
  • Short sleep prevalence was 36.2% among workers working over 40 hours weekly versus 27.7% among those working 40 hours or less (2010; U.S. civilian employed adults). (Short Sleep Duration Among Workers…)
  • Across all shifts, manufacturing workers had 34.1% short sleep versus 24.1% in the other-services sector (2010; U.S. civilian employed adults by industry). (Short Sleep Duration Among Workers…)
  • Among night-shift workers, short sleep was 69.7% in transportation and warehousing and 52.3% in health-care and social assistance (2010; U.S. night-shift workers by industry). (Short Sleep Duration Among Workers…)
  • Among night-shift workers, short sleep was 9.8% in arts, entertainment and recreation (2010; U.S. night-shift workers). (Short Sleep Duration Among Workers…)
  • The NHIS 2010 analysis used 15,214 employed adults and had a final sample adult response rate of 60.8% (U.S. civilian employed adults). (Short Sleep Duration Among Workers…)

Average ≤6 hours; age-stratified cross-sectional estimates.

Age 65+ night-shift estimate was suppressed/unstable in the table.

Self-reported average sleep.

Observational subgroup estimate.

Race/ethnicity categories and self-reported sleep; associations are not causal.

Cross-sectional marital-status comparison.

Educational categories are observational correlates.

Self-reported sleep and job count.

Work hours and sleep were measured observationally.

Broad industry groupings; some subgroup estimates are less stable.

Industry-specific estimates; not a causal industry effect.

Small or heterogeneous industry subgroup; interpret with survey uncertainty.

Sample size is contextual rather than an outcome; response rate may affect representativeness.

Circadian rhythm sleep-disorder prevalence and adolescent timing

Review reports estimates from underlying studies; diagnostic definitions and ascertainment vary.

Range comes from cited studies, not one nationally representative survey.

Clinic population is not representative of all people with insomnia.

Light exposure, melatonin and measurable circadian phase shifts

  • A controlled light study enrolled 39 healthy young adults, including 16 women, with mean age 22.18±3.62 years (9-day inpatient experiment). (Human responses to bright light…)
  • A 0.2-hour bright-light exposure produced a 1.07±0.36-hour phase delay in the reported comparison (controlled experiment; healthy young adults). (Human responses to bright light…)
  • A 4.0-hour bright-light exposure produced a 2.65±0.24-hour phase delay (controlled experiment; healthy young adults). (Human responses to bright light…)
  • Per minute, the 0.2-hour exposure was reported as over five times more effective at phase delaying the pacemaker than the 4-hour exposure (controlled experiment; healthy young adults). (Human responses to bright light…)
  • The light trial used a 4.5-hour controlled-posture episode centered within a 16-hour wake episode (controlled experiment; healthy young adults). (Human responses to bright light…)
  • The study used three baseline days, an 8-hour sleep episode after exposure and a second circadian phase assessment (9-day inpatient experiment; healthy young adults). (Human responses to bright light…)

Small, young, healthy inpatient sample.

Phase measured by change in dim-light melatonin onset; timing-specific response.

Laboratory trial; not a universal dose-response rule.

Authors’ dose-normalized comparison; not a clinical treatment recommendation.

Protocol timing and posture constrain generalizability.

Protocol detail, not a population outcome; included to define the measurement context.

Circadian rhythm aging, rest-activity regularity and biological age

Cross-sectional observational analysis of accelerometry and physiology.

Association, not proof that stronger rhythms slow aging; age is algorithmic.

Adjusted observational association.

Interpretation follows the study’s modeled direction; rhythm metrics are not direct clock measurements.

Adjusted cross-sectional association.

Statistical significance does not establish causality or clinical benefit.

Molecular circadian rhythms across human tissues and chronotypes

  • In postmortem human prefrontal cortex from 146 individuals, about 10% of detected transcripts showed significant circadian rhythmicity (human postmortem study). (Effects of aging on circadian…)
  • A meta-analysis across two prefrontal-cortex areas identified 235 genes with significant circadian expression rhythms (human postmortem study; human prefrontal cortex). (Effects of aging on circadian…)
  • Of the 235 core rhythmic genes, 217 (92%) had phase concordance within the reported ±4-hour interval between the two brain areas (human postmortem study; human prefrontal cortex). (Effects of aging on circadian…)
  • Age-dependent rhythmicity changes were identified in 1,186 genes in BA11 and 1,591 genes in BA47 (human postmortem study; human prefrontal cortex). (Effects of aging on circadian…)
  • In a chronotype study, Per3 expression phase differed by 2.61 hours between extreme morning and evening types (human participants with extreme chronotypes). (Diurnal Preference Predicts Phase Differences…)
  • Nr1d2 expression phase differed by 3.08 hours between extreme morning and evening types (chronotype study; human participants with extreme chronotypes). (Diurnal Preference Predicts Phase Differences…)
  • The Per3 time effect had F=24.73 (p<0.001), and its time-by-chronotype interaction had F=3.29 (p=0.05) (chronotype study; human participants with extreme chronotypes). (Diurnal Preference Predicts Phase Differences…)
  • The Nr1d2 time effect had F=21.8 (p<0.001), and its time-by-chronotype interaction had F=5.89 (p=0.008) (chronotype study; human participants with extreme chronotypes). (Diurnal Preference Predicts Phase Differences…)
  • In luteinized granulosa cells, older women had PER1 expression of 0.27±0.14-fold relative to the comparison group (p=0.03) (young versus older women study; human ovarian granulosa cells). (Is the aging human ovary…)
  • In the same granulosa-cell study, older women had CLOCK expression of 0.29±0.16-fold relative to the comparison group (p=0.05) (young versus older women study; human ovarian granulosa cells). (Is the aging human ovary…)

Postmortem time-of-death design and brain tissue; not whole-body prevalence.

Transcriptomic discovery threshold q<0.05; tissue-specific finding.

Concordance is between sampled brain regions, not individuals’ sleep schedules.

Age-related transcriptomic changes from postmortem tissue; mechanisms remain observational.

Expression phase in sampled peripheral tissue; group comparison, not a population prevalence.

Peripheral gene-expression measure; chronotype classification and sample size limit generalization.

Inferential statistics from one study; not effect-size estimates of population prevalence.

Inferential statistics from one study.

Preliminary cell study; fold-change reference and age-group composition are study-specific.

Preliminary, tissue-specific and borderline statistical result.

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