# Caffeine: timing is the lever

Rested + caffeinated > deprived + caffeinated. A coffee needs ~8–9 h before bed.



## Takeaways

- Sleep first, then caffeine.

- Last coffee ≥ 8 h before bed; pre-workout ≥ 12 h.

- Log doses — the effect is invisible from the inside.



A meta-analysis (Galpin cites colleague Dr Ben House's work; see also McLellan 2016) shows: sleep deprivation lowers physical and cognitive performance; caffeine brings you back to about baseline; but it doesn't return you to the augmented, rested-and-caffeinated state. You'll feel as good, but you won't perform as well. There are no free passes in physiology.

How late is too late? 400 mg taken 6 hours before bed still cut objective sleep by over an hour — and subjects didn't notice. The 2023 meta-analysis puts the cutoff at ~8.8 h before bed for a standard coffee (~107 mg) and ~13 h for a pre-workout dose (~217 mg). Habitual users are less sensitive but not immune, and genetics matter.

SleepShred logs each dose with time and mg, computes your personal cutoff from your typical bedtime, and compares nights after late caffeine with the rest.



## Sources

- Caffeine effects on sleep taken 0, 3, or 6 hours before going to bed (Drake C, Roehrs T, Shambroom J, Roth T, 2013)

- The effect of caffeine on subsequent sleep: a systematic review and meta-analysis (Gardiner C, Weakley J, Burke LM, et al., 2023)

- Coffee, caffeine, and sleep: a systematic review of epidemiological studies and randomized controlled trials (Clark I, Landolt HP, 2017)

- A review of caffeine's effects on cognitive, physical and occupational performance (McLellan TM, Caldwell JA, Lieberman HR, 2016)

- Sustaining executive functions during sleep deprivation: a comparison of caffeine, dextroamphetamine, and modafinil (Killgore WDS, Kahn-Greene ET, Grugle NL, Killgore DB, Balkin TJ, 2009)

- Wake up and smell the coffee: caffeine supplementation and exercise performance — an umbrella review of 21 published meta-analyses (Grgic J, Grgic I, Pickering C, Schoenfeld BJ, Bishop DJ, Pedisic Z, 2020)

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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.

SleepShred for iPhone: https://apps.apple.com/app/id6802040541