Caffeine and Sleep

Caffeine blocks adenosine receptors, masking sleep pressure rather than removing it. With a half-life around five to six hours, a 3 p.

m. double shot still leaves roughly half its caffeine circulating at 9 p.

m. , which delays sleep onset and trims deep sleep even when you fall asleep on time.

Sensitivity varies widely with genetics, age, and habitual intake, so find your personal cutoff by moving the last cup earlier in thirty-minute steps and watching sleep onset for a week. Protect the eight hours before bed as a starting rule.