Caffeine consumption, insomnia, and sleep duration: Results from a nationally representative sample

• Insomnia symptoms were associated with caffeine consumption in unadjusted models.
• Race/ethnicity and anxiety explain the association of insomnia symptoms and caffeine.
• Interaction between high caffeine and sleep duration was associated with non-restorative sleep.

ObjectiveInsomnia 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.MethodsData 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.ResultsThe 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.ConclusionThe association between caffeine use and insomnia symptoms depends on habitual sleep duration at a population level.