Evening Caffeine Trims Deep Sleep, Warns New Sleep Research
A review of 32 caffeine-related sleep studies shows caffeine reduces slow-wave, non-REM deep-sleep brain activity and increases wakeful sleep patterns, even when people get 7–9 hours of sleep or feel rested. The effects vary with dose and timing, and depend on individual sleep quality, suggesting total daily caffeine intake and how quickly it metabolizes before nightfall matter. Limiting caffeine, not just avoiding it late, may help protect sleep quality.
