Frequently Asked Questions
What is a sleep cycle?
A sleep cycle lasts approximately 90 minutes and includes light sleep, deep sleep, and REM sleep stages. Waking at the end of a cycle helps you feel refreshed.
How many hours of sleep do I need?
Adults need 7-9 hours of sleep (4-6 complete sleep cycles). It takes about 15 minutes to fall asleep, which should be factored in.
What happens with sleep deprivation?
Lack of sleep impairs concentration, weakens immunity, promotes weight gain, and affects mood. Chronic sleep deprivation has serious long-term health consequences.
Updated 2026 — WHO standards