We spend roughly a third of our lives asleep, yet most of us have no idea what happens during those hours. The truth: sleep is not a single state but a repeating cycle of stages, each doing distinct repair work.
A full cycle lasts about 90 minutes and repeats four to six times a night. It begins with light sleep, descends into deep slow-wave sleep — when growth hormone is released and the immune system does heavy maintenance — then rises into REM, the vivid dreaming stage where memories are consolidated.
Why waking matters
Waking mid-cycle, especially from deep sleep, is why a 20-minute alarm can leave you groggier than no nap at all. Sleep researchers suggest timing rest in ~90-minute multiples, or keeping naps under 25 minutes.
Small levers, big difference
Consistent wake times, morning daylight, and a cool, dark bedroom do more for sleep quality than any gadget. Your cycles will thank you.
Note: this article is for general information only and is not medical advice. Consult a professional about sleep concerns.