Caffeine effects on sleep taken 0, 3, or 6 hours before going to bed.
Level 2 - randomized trial
Individual randomized controlled trial
PubMed 24235903 · doi:10.5664/jcsm.3170
What was done
A randomized, placebo-controlled trial compared the sleep-disruptive effects of a fixed 400 mg dose of caffeine administered at 0, 3, and 6 hours prior to habitual bedtime versus placebo in a home setting. Sleep disturbance was measured using both self-reported sleep measures and an objective validated portable sleep monitor.
What was found
Caffeine taken at 0, 3, and 6 hours prior to bedtime each produced statistically significant sleep disturbance relative to placebo (p < 0.05 for all). The abstract reports a reduction in total sleep time even at 6 hours prior to bedtime, but provides no specific numerical values, confidence intervals, or effect sizes.
Why it matters
This study provides objective, home-environment empirical support for sleep hygiene guidelines recommending the avoidance of substantial caffeine intake for at least 6 hours before bedtime.
Limits
The abstract does not report sample size, participant demographics, baseline caffeine tolerance, or exact numerical values for sleep outcomes. Only a single fixed dose (400 mg) was tested.
Cited by
- supports Drinking caffeine within 8 to 10 hours before sleep disrupts sleep, even if a person can fall asleep easily.