Abstract
BACKGROUND: Adequate sleep and physical activity promote longevity among older adults. Caffeine supplementation could be used to increase activity levels, but its effects have not been examined in real-world settings where potential trade-offs regarding sleep quality are also considered. This study sought to examine associations between caffeine intake and accelerometer-derived sleep and activity among older adults under free-living conditions. METHODS: Cross-sectional data were gathered from older adults aged 65 + in the 2011-14 National Health and Nutrition Examination Surveys (NHANES). Sleep parameters were derived from accelerometer data using a data-driven machine learning approach. Caffeine consumption was categorized based on weight (in mg/kg: 0, > 0 to 1, > 1 to 2, > 2 to 3, > 3) and absolute consumption (in mg: 0, > 0 to 100, > 100 to 200, > 200 to 300, > 300). Multivariable survey weighted regression models were used to examine associations between caffeine with average total daytime activity, highly active minutes, sleep duration, and sleep efficiency. Covariate adjustments included demographics, body mass index, smoking, alcohol, sleep disorders, sleep parameters (for activity outcomes), and daytime activity (for sleep outcomes). RESULTS: N = 1,629 NHANES participants were included. Caffeine consumption was highest in the morning. In adjusted models, older adults who consumed > 3 mg/kg were 16.5% more active during the day (95% CI: 9.0, 24.4) and were highly active for 42.8 additional minutes (95% CI: 20.3, 65.4) compared to non-consumers. Similar results were observed for absolute consumption (mg), and significant but lower magnitude effects were observed for lower levels of consumption. Caffeine showed no association with sleep efficiency, while low levels of consumption (≤ 1 mg/kg, ≤ 200 mg) were associated with longer sleep duration. CONCLUSIONS: Under free-living dietary, sleep, and activity patterns, this study found older adults who consumed caffeine were more active than non-consumers. Overall consumption was not associated with sleep efficiency but was associated with longer sleep duration at ≤ 1 mg/kg and ≤ 200 mg. Future causal studies should determine the effectiveness of caffeine for promoting higher activity in older adult populations.