Caffeine Timing

Research summary

• A randomized crossover trial directly tested caffeine dose and timing before bed and found it prolonged sleep latency and reduced total sleep time in a dose- and timing-dependent way, and this is reinforced by a systematic review of caffeine and sleep across epidemiological and randomized studies reaching similar conclusions.
• Some other referenced studies in this set concern general sports-nutrition timing or supplementation topics not specific to caffeine and sleep, and are less directly relevant.
• The core caffeine-and-sleep relationship is supported by both a controlled experimental trial and a systematic review, which is a reasonably strong combination, though the evidence on precisely how many hours before bed caffeine should be avoided is still somewhat individual and not fully standardized.