Caffeine won back what a short night cost, more with a bigger dose
Pooling 45 studies, caffeine restored reaction time, attention and driving in people cut to six hours of sleep or kept awake a full day, and bigger doses brought bigger gains.
What the study found
Caffeine gave back the reaction time and focus that lost sleep took
This is caffeine as a repair for lost sleep. Pooling 45 studies, caffeine reliably restored reaction time, attention, planning and vehicle control in people cut to six hours or less or kept awake a full day, and the larger the dose, the larger the recovery.
The caveat · Well-rested people never tested
Everyone in these 45 studies was short on sleep, at six hours or under or awake for a full day, so nothing here says what caffeine does for someone who slept well. The benefit kept rising with dose without the review ever finding the point where it stops rising, so the top of that range is unmapped.