Trends in the prevalence of short sleepers in the USA: 1975-2006.
OBJECTIVE
To determine (1) whether short sleep has increased over 31 years; (2) whether trends in short sleep differed by employment status; (3) which sociodemographic factors predict short sleep; and (4) how short sleepers spend their time.


METHODS
Time diaries from eight national studies conducted between 1975 and 2006.


METHODS
U.S. adults > or = 18 years.


RESULTS
Short sleepers were defined as those reporting < 6 hours of sleep in their time diary. Unadjusted percentages of short sleepers ranged from 7.6% in 1975 to 9.3% in 2006. The 1998-99 study had the highest odds of short sleep. The odds ratio for the 31-year period predicting short sleep was 1.14 (95% CI: 0.92, 1.50, P = 0.22), adjusting for age, sex, education, employment, race, marital status, income, and day of week. When stratified by employment, there was a significant increase for full-time workers (P = 0.05), who represented over 50% of participants in all studies, and a significant decrease for students (P = 0.01), who represented < 5% of participants. The odds of short sleep were lower for women, those > or = 65 years, Asians, Hispanics, and married people. The odds were higher for full-time workers, those with some college education, and African Americans. Short sleepers in all employment categories spent more time on personal activities. Short sleepers who were full- and part-time workers spent much more time working.


CONCLUSIONS
Based on time diaries, the increase in the odds of short sleep over the past 31 years was significant among full-time workers only. Work hours are much longer for full-time workers sleeping < 6 hours.
Knutson
Kristen L
KL
Department of Medicine, University of Chicago, Chicago, IL 60637, USA. kknutson@medicine.bsd.uchicago.edu
Van Cauter
Eve
E
Rathouz
Paul J
PJ
DeLeire
Thomas
T
Lauderdale
Diane S
DS
D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000368:Aged; D003430:Cross-Sectional Studies; D004651:Employment; D005260:Female; D006306:Health Surveys; D006801:Humans; D015994:Incidence; D008019:Life Style; D008297:Male; D008875:Middle Aged; D016017:Odds Ratio; D012737:Sex Factors; D012892:Sleep Deprivation / Q000453:epidemiology*; D012959:Socioeconomic Factors; D014481:United States; D055815:Young Adult