How many studies support Caffeine Timing?

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 backed by 3 published studies in Vitaebase's database, including 1 randomized controlled trial, the most recent from 2026 -- a modest but real research base.