Evaluating the association between caffeine exposure and sleep duration and trouble sleeping in adults.

Study Objectives: This study examines whether caffeine is independently associated with sleep outcomes in the general population. Methods: Data from the National Health and Nutrition Examination Survey from 2005 to 2018 were analyzed, including adults aged ≥18 years who completed both dietary interviews and the Sleep Disorders Questionnaire. Caffeine exposure was estimated from a 24-h dietary recall and expressed as milligrams per day, modeled both continuously and categorically (0, 1-99, 100-399, and ≥ 400 mg/day). Sleep outcomes included self-reported sleep duration (<6 h vs. ≥6 h). Survey-weighted multivariable logistic regression models were applied to examine associations, adjusting for age, sex, race/ethnicity, education, smoking status, alcohol use, income-to-poverty ratio, and depression. Results: The sample included 37 469 adults (mean age 46.4 years; 51.7 per cent female). Compared with 0 mg/day, the adjusted odds ratios (aORs) for short sleep were 1.0 (95 per cent CI, 0.9-1.2) for 1-99 mg/day, 1.1 (95 per cent CI, 0.9-1.2) for 100-399 mg/day and 1.5 (95 per cent CI, 1.2-1.8) for ≥400 mg/day. Caffeine intake of 101-400 mg taken within 8 h of bedtime was associated with short sleep. Although significant in unadjusted analyses, the association between caffeine intake and self-reported trouble sleeping was no longer significant after multivariable adjustment (low intake: aOR 1.0 [95 per cent CI, 0.9-1.1]; moderate intake: aOR 1.0 [95 per cent CI, 0.9-1.2]; high-intake: aOR 1.0 [95 per cent CI, 0.9-1.2]). Conclusions: In this U.S. cross-sectional sample, higher caffeine intake was modestly associated with shorter self-reported sleep duration particularly when taken within 8 h of bedtime.