Is Caffeine Timing good for sleep quality?

The evidence points that way, though it's not yet conclusive. 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. That's reflected in an evidence score of 47/100 for its role in sleep quality, drawn from 3 studies (1 RCT), with an estimated impact on longevity rated moderate (36/100).