Age- and dose-specific effects of caffeine on sleep: A meta-analysis of controlled crossover trials.
Level 1 - systematic review of randomized trials
Meta-analysis of controlled crossover trials
PubMed 41124973 · doi:10.1016/j.sleep.2025.106874
What was done
Authors searched PubMed, Web of Science, CINAHL, and the Cochrane Library through March 25, 2025, for controlled crossover trials assessing the effects of acute caffeine versus placebo on nighttime polysomnography in healthy adults. Twenty-two trials comprising 956 participants were analyzed using random-effects meta-analysis, subgroup analyses (by age and dose), and mixed-effects meta-regressions.
What was found
Caffeine significantly reduced total sleep time (mean difference [MD] = -34.67 min), decreased sleep efficiency (MD = -4.74%), reduced slow-wave sleep percentage (MD = -1.01%), and prolonged sleep onset latency (MD = +8.35 min). Changes in REM percentage were not statistically significant. Total sleep time decreased in both young and middle-aged groups and under both low- and high-dose conditions. High-dose caffeine additionally decreased slow-wave sleep percentage. However, subgroup differences were not statistically significant, and meta-regressions found no significant linear relationship with continuous age or dose.
Why it matters
This study provides precise pooled effect sizes from objective polysomnography trials, demonstrating that acute caffeine ingestion reduces sleep duration by over half an hour and degrades both sleep efficiency and slow-wave restorative sleep.
Limits
The findings reflect acute caffeine administration in healthy adults and cannot be generalized to chronic consumption, habituated users, or clinical populations with sleep disorders. Meta-regressions failed to detect statistically significant continuous dose-response or age-dependent gradients.