Caffeine: what the research actually says

Caffeine works on your sleep for far longer than it works on your alertness — the reason a personal cutoff time beats a rule of thumb.

All studies · 6

The effect of caffeine on subsequent sleep: a systematic review and meta-analysisGardiner C, Weakley J, Burke LM, et al. · Sleep Medicine Reviews 69:101764 · 2023Caffeine reduced total sleep by ~45 min and efficiency by 7%. To avoid effects, a coffee (~107 mg) should be ~8.8 h before bed; a pre-workout dose (~217 mg) ~13 h.Wake up and smell the coffee: caffeine supplementation and exercise performance — an umbrella review of 21 published meta-analysesGrgic J, Grgic I, Pickering C, Schoenfeld BJ, Bishop DJ, Pedisic Z · British Journal of Sports Medicine 54(11):681–688 · 2020Caffeine is ergogenic for endurance, strength and power — which is why timing (not abstinence) is the lever.Coffee, caffeine, and sleep: a systematic review of epidemiological studies and randomized controlled trialsClark I, Landolt HP · Sleep Medicine Reviews 31:70–78 · 2017Caffeine prolongs sleep latency, reduces total sleep and deep sleep; sensitivity varies with genetics and habitual use.A review of caffeine's effects on cognitive, physical and occupational performanceMcLellan TM, Caldwell JA, Lieberman HR · Neuroscience & Biobehavioral Reviews 71:294–312 · 2016Caffeine restores performance lost to sleep deprivation but does not exceed the rested baseline — no free passes.Caffeine effects on sleep taken 0, 3, or 6 hours before going to bedDrake C, Roehrs T, Shambroom J, Roth T · Journal of Clinical Sleep Medicine 9(11):1195–1200 · 2013400 mg caffeine taken even 6 h before bed cut objective sleep by >1 h — while subjects barely noticed.Sustaining executive functions during sleep deprivation: a comparison of caffeine, dextroamphetamine, and modafinilKillgore WDS, Kahn-Greene ET, Grugle NL, Killgore DB, Balkin TJ · Sleep 32(2):205–216 · 2009Stimulants patch alertness but not higher-order judgement after sleep loss.

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Caffeine: timing is the lever

Frequently asked questions

What does the research say about caffeine?

400 mg caffeine taken even 6 h before bed cut objective sleep by >1 h — while subjects barely noticed.

How do I track caffeine?

SleepShred logs it in about 20 seconds a day and then compares your nights with and without it, so you see the effect on your own sleep instead of the study average.

Is SleepShred free?

No. SleepShred Pro is $4.99 per month or $29.99 per year, with no free trial and no ads. Everything stays on your iPhone.

Track it, don't guess it

SleepShred turns this research into a 20-second daily habit: log your night, see which of your own behaviours move your sleep, and screen for the disorders nobody diagnoses.

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Educational summary of published research, not medical advice. Screening scores are not diagnoses. If a score is elevated or you feel unwell, talk to a clinician.