title: Caffeine consumption, insomnia, and sleep duration: Results from a nationally representative sample.
abstract: OBJECTIVE
  Insomnia symptoms have been individually associated with both caffeine consumption and sleep duration abnormalities in prior studies. The goal of this study was to determine whether caffeine consumption was associated with insomnia symptoms from a population perspective and whether this relationship depended on habitual sleep duration.
  
  
  METHODS
  Data were extracted from the 2007-2008 National Health and Nutritional Examination Survey (N = 4730). Caffeine consumption was quantified as mg/d from 2 typical days of use, 7 to 10 d apart. Insomnia symptoms were evaluated using frequencies of difficulty falling asleep (DFA), difficulty staying asleep (DSA), non-restorative sleep (NRS), and daytime sleepiness (DS). Habitual sleep duration was assessed as the hours of sleep obtained on a typical night. Binomial logistic regression analysis evaluated the relationships of individual insomnia and sleepiness symptoms (DFA, DSA, NRS, and DS) with caffeine consumption and sleep duration variables, after adjusting for covariates.
  
  
  RESULTS
  The mean ± SD caffeine consumption was 176.6 ± 201 mg/d. Mean habitual sleep duration was 6.8 ± 1.4 h. Insomnia symptoms were prevalent in 19.1% to 28.4% of the respondents. Although caffeine consumption was associated with all insomnia symptoms in the unadjusted models, the adjusted models demonstrated a trend toward significance with DSA. Sleep duration was inversely associated with the insomnia symptoms in unadjusted and adjusted analysis. Finally, NRS was associated with an interaction between increased caffeine consumption and sleep duration.
  
  
  CONCLUSIONS
  The association between caffeine use and insomnia symptoms depends on habitual sleep duration at a population level.
authors.affiliation: Department of Emergency Medicine, UAB School of Medicine, Birmingham, AL; Department of Epidemiology, UAB School of Public Health, Birmingham, AL. Electronic address: Drninadsc@gmail.com.
authors.forename: Ninad S
authors.initials: NS
authors.lastname: Chaudhary
authors.affiliation: University of Arizona College of Medicine, Tucson, AZ.
authors.forename: Michael A
authors.initials: MA
authors.lastname: Grandner
authors.affiliation: University of Southern California, Los Angeles, CA.
authors.forename: Nicholas J
authors.initials: NJ
authors.lastname: Jackson
authors.affiliation: Corporal Michael J. Crescenz VA Medical Center, Philadelphia, PA; Perelman School of Medicine of the University of Pennsylvania, Philadelphia, PA.
authors.forename: Subhajit
authors.initials: S
authors.lastname: Chakravorty
mesh_terms: D000328:Adult; D002110:Caffeine / Q000008:administration & dosage* / Q000009:adverse effects*; D000697:Central Nervous System Stimulants / Q000008:administration & dosage / Q000009:adverse effects; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009749:Nutrition Surveys; D015995:Prevalence; D012890:Sleep / Q000187:drug effects* / Q000502:physiology; D007319:Sleep Initiation and Maintenance Disorders / Q000453:epidemiology / Q000209:etiology* / Q000503:physiopathology*; D014481:United States / Q000453:epidemiology; D055815:Young Adult
chemical_list: D000697:Central Nervous System Stimulants; D002110:Caffeine
keywords: Anxiety; Caffeine; Population; Sleep deprivation; Sleep initiation and maintenance disturbance