How Sleep Works: Stages, Cycles and a Normal Night
The four sleep stages, the 90-minute cycle, the two systems that decide when you sleep, how needs change with age, and what a normal night looks like — including the wakings you forget.
Independent sleep education · founded by a sleep physician
Understand the night. Own the morning.
Complete Sleep explains how sleep actually works — in plain language, backed by evidence, with realistic next steps you can start tonight. No miracles, no products, no clinic.
How did you sleep last night?
Let’s look at what keeps you up
Most bad nights have an engine — a racing mind, an irregular schedule, or a body clock out of step with the day. Start with the guide that fits.
Time in bed isn’t the same as sleep
Waking unrefreshed after a full night points to quality, not quantity — and sometimes to breathing during sleep. Two places to start.
Good — let’s make it reliable
The habits that protect good sleep are small and unglamorous. These are the ones with the best evidence behind them.
- Founded by a board-certified sleep physician, its medical reviewer
- Every article dated and sourced · 0 of 30 medically reviewed so far
- No products no clinic, no sales pitch — education only
Night to morning — the whole point.
01 — Where to begin
Where would you like to begin?
Pick the situation that sounds most like yours. Each path starts with one clear article and builds from there.
01I lie awake with a racing mindStress and sleep feed each other. Learn why, and how to switch off in the evening.Calm the evening02I sleep, but wake up exhaustedTime in bed and quality sleep are not the same thing. Find out what “good sleep” means.Understand sleep quality03I snore, or I’ve been told I stop breathingA plain explanation of sleep apnea, a 2-minute self-check, and how testing works.Learn about sleep apnea04I just want a better routineSmall, repeatable habits — morning, day, and evening — that add up over a few weeks.Build better habits
02 — Latest
Latest articles
New articles are added regularly. Each one shows who wrote it, its medical-review status, when it was last updated, and where the information comes from.
03 — Who writes this
Who writes this
Complete Sleep was founded by Dr. Adekunle “Ade” Ajisebutu, a board-certified sleep physician at MercyOne East Village Sleep Medicine in Des Moines, Iowa. He started the site because reliable sleep information is surprisingly hard to find, and most of what turns up first is selling something.
Articles are written by the Complete Sleep editorial team from clinical guidelines and peer-reviewed research, and each one shows whether Dr. Ajisebutu has reviewed it and when. Nothing here is a diagnosis or a treatment plan. It is the explanation you wish you had before your next appointment.
Dr. Adekunle Ajisebutu, MD · Sleep Physician · MercyOne East Village Sleep Medicine
Public provider profiles
Complete Sleep is independent and is not affiliated with or endorsed by MercyOne or WebMD.
04 — A two-minute check
Wondering about sleep apnea? Take the 2-minute STOP-Bang self-check.
STOP-Bang is a validated screening questionnaire used by clinicians worldwide. It cannot diagnose anything, but it gives you a clear, evidence-based starting point for a conversation with your doctor. Nothing you enter is stored or sent anywhere.
05 — Browse
Browse by topic
- Sleep basicsHow sleep works, what “good sleep” actually means, and how much you need.7 articles
- Sleep hygiene & daily habitsThe daytime and evening habits that make restful sleep more likely.8 articles
- Bedtime routines & eveningsHow to wind down, what to do in the last hour, and waking up well.3 articles
- Stress, mood & sleepWhy a racing mind keeps you up, and how sleep and mental health affect each other.3 articles
- Food, drink & sleepCaffeine, alcohol, meal timing, and what actually helps.3 articles
- Sleep apnea & sleep testingSnoring, sleep apnea, screening questionnaires, and how sleep tests work.6 articles
- Insomnia & sleep problemsTrouble falling or staying asleep, and the conditions that hide behind it.8 articles
- Travel, shift work & seasonsJet lag, night shifts, clock changes, winter darkness and summer heat.6 articles
06 — Where you live
Sleep is local, too
How much daylight your city gets, how to get a sleep study where you live, and the sleep problems that come with living there.
- Toronto8.9–15.4 h daylight
- Ottawa8.7–15.7 h daylight
- Vancouver8.2–16.2 h daylight
- Calgary7.9–16.6 h daylight
- Edmonton7.5–17 h daylight
- Montreal8.7–15.7 h daylight
- Winnipeg8.1–16.4 h daylight
- New York City9.3–15.1 h daylight
- Chicago9.1–15.2 h daylight
- Los Angeles9.9–14.4 h daylight
- Houston10.2–14.1 h daylight
- Boston9.1–15.3 h daylight
07 — How we work
How we work
Evidence over trends
Articles draw on clinical guidelines and peer-reviewed research, and we say so when the evidence is thin.
Plain language
If a sentence needs a medical dictionary, we rewrite it.
Realistic expectations
Habits take weeks. Some problems need a clinician. We tell you which is which.
Nothing to sell
No supplements, no devices, no bookings. Just clear explanations.