Afternoon caffeine cutoff
No caffeine after 2pm: half-life is 5–7 hours, longer in slow metabolisers.
Why
Caffeine blocks adenosine receptors that signal sleep pressure. With a half-life of 5–7 hours (longer in some genotypes), an afternoon coffee can leave a quarter of the dose still active at bedtime. Effect on sleep architecture (less deep sleep) is measurable even when subjective sleep feels fine.
Slot in your day
How to do it
How
Last caffeine by 2pm if you sleep around 11pm. Adjust earlier if you metabolise slowly (genetic variation in CYP1A2). Switch to decaf or herbal alternatives in the afternoon.
Sticking with it
Pre-stage a tasty afternoon non-caffeine drink. Removing without replacing fails.
Markers this may influence
Evidence
Drake 2013 J Clin Sleep Med (within-subject lab study): 400 mg caffeine taken 6 hours before bed still measurably disrupted polysomnography-assessed sleep: total sleep time fell by ~1 hour vs placebo, even when taken hours before bedtime. The 5–7 hour half-life puts a meaningful fraction of an afternoon dose into the sleep window.