Sleep Cycles Explained
Each sleep cycle lasts approximately 90 minutes and includes: light sleep (N1, N2), deep sleep (N3/SWS), and REM sleep. Waking up mid-cycle causes grogginess; waking at cycle end feels refreshing.
The 90-Minute Rule
Plan sleep in multiples of 90 minutes. For a 7:00 AM wake-up, ideal bedtimes are 11:30 PM (5 cycles), 10:00 PM (6 cycles), or 1:00 AM (4 cycles). Add ~14 minutes to fall asleep.
Recommended Sleep Duration
- Adults (18–64): 7–9 hours (4–6 cycles)
- Teens (14–17): 8–10 hours
- Children (6–13): 9–11 hours
- Seniors (65+): 7–8 hours
Sleep Hygiene Tips
- Keep a consistent sleep schedule (even on weekends)
- Avoid screens 1 hour before bed (blue light blocks melatonin)
- Keep bedroom cool (18–22°C), dark, and quiet
- Avoid caffeine after 2 PM and heavy meals before bed
- Exercise regularly but not within 3 hours of bedtime
Signs of Poor Sleep
Daytime drowsiness, difficulty concentrating, irritability, weakened immunity, and weight gain are all signs you may not be getting enough quality sleep. Track your cycles for optimal rest.