localStorage), so you can close the tab and resume. Everything else is reference. Start with the two highest-leverage levers: a fixed wake time and morning light.
Quick Reference — the highest-leverage numbers
| Lever | Target | Why / note |
|---|---|---|
| Adult sleep need | 7–9 h (≥7 h on a regular basis) | AASM/SRS consensus, ages 18–60. Teens 8–10 h; kids 6–12: 9–12 h. |
| Regularity | Same wake time ±30 min, 7 days/wk | Sleep consistency predicted mortality more strongly than duration (SLEEP, 2024). |
| Morning light | 10–30 min outdoor within ~1 h of waking | Outdoor daylight is 10,000–100,000 lux vs ~500 indoors — it anchors your clock. |
| Caffeine cutoff | ≥8–10 h before bed (often ≤2 pm) | Half-life ~5 h (range 1.5–9.5). 400 mg even 6 h pre-bed cut sleep ~41 min. |
| Alcohol | None within 3–4 h of bed | Sedates you fast, then fragments the night and suppresses early REM. |
| Bedroom temp | ~18 °C / 65 °F (range 16–20 °C) | Core-temp drop is a sleep trigger; cool, dark, quiet. |
| Screen / bright light | Dim & warm 2–3 h before bed | Brightness & engagement matter more than "blue light" alone. |
| Melatonin (if used) | 0.5–1 mg, 2–3 h before target sleep | A timing signal, not a sleeping pill. Higher doses aren't better. |
| Nap | 10–20 min, early–mid afternoon | Avoid >30 min or naps after ~3 pm (steals sleep pressure). |
| Sleep cycle | ~90 min, 4–6 per night | Deep sleep front-loaded; REM back-loaded (so a short night cuts REM most). |
| Chronic insomnia (1st-line) | CBT-I, not sleeping pills | ACP & AASM: more durable than medication, fewer harms. |
| Wind-down | 30–60 min screen-light, low-stimulation | Consistency trains the brain that bed = sleep. |
Fundamentals
How sleep works — the mental model
The two-process model: sleep pressure × the clock
When and how well you sleep is governed by two systems running in parallel (Borbély's model):
- Process S — sleep pressure (homeostatic). A molecule called adenosine builds up in the brain the longer you're awake, creating drowsiness. Sleep clears it. Caffeine works by blocking adenosine receptors — it masks pressure, it doesn't remove it, so the "crash" comes when it wears off.
- Process C — the circadian rhythm (the clock). A ~24-hour timer in the brain's suprachiasmatic nucleus (SCN) sets your alertness rhythm, core body temperature, and melatonin release. Its master input ("zeitgeber") is light.
Good sleep = high sleep pressure (enough hours awake, no late caffeine/naps) meeting a well-timed clock (consistent schedule, morning light, dark evenings). Fight either one — nap at 6 pm, or stare at a bright phone at midnight — and you sleep worse even when tired.
Sleep stages & architecture (N1, N2, N3, REM)
Sleep isn't uniform. You cycle through stages, each doing different work:
| Stage | ~% of night | What it is | What it's for |
|---|---|---|---|
| N1 (light) | ~5% | Drift-off; easily woken; the "falling" jerk. | Transition only. |
| N2 (light) | ~45–55% | Sleep spindles & K-complexes; body cools, HR drops. | Motor-skill memory; bulk of the night. |
| N3 (deep / slow-wave) | ~13–23% | Big slow delta waves; very hard to wake; grogginess if woken. | Physical recovery, immune function, glymphatic "clean-out," declarative memory. |
| REM | ~20–25% | Vivid dreams; brain active, body paralyzed (atonia); eyes dart. | Emotional processing, creativity, memory integration. |
Rough proportions for a healthy adult night. Newborns spend ~50% in REM; REM share falls with age, and N3 deep sleep declines markedly after ~age 60.
Cycles & the hypnogram: why a short night robs REM
You move through ~90-minute cycles, 4–6 times a night — but the mix shifts across the night:
- First third of the night is rich in deep N3 sleep (physical restoration). This is why an early bedtime that you keep matters, and why deep sleep is largely "protected."
- Last third is rich in REM, in progressively longer bouts toward morning.
Circadian rhythm: light, melatonin, temperature & cortisol
Four signals choreograph the 24-hour cycle. Align them and sleep gets easy; scramble them (shift work, jet lag, midnight scrolling) and it falls apart.
- Light — the master clock-setter. Bright light in the morning advances the clock (earlier sleep); bright light at night delays it (later sleep). Special melanopsin cells in the retina sense this independent of vision.
- Melatonin — the "it's dark, prepare for sleep" hormone. Onset (DLMO) is ~2–3 h before natural sleep; light at night suppresses it. Supplemental melatonin works mainly by shifting timing, not by sedating.
- Core body temperature — peaks early evening, then falls ~0.5–1 °C to enable sleep, bottoming ~2 h before wake. A warm bath/shower 1–2 h before bed paradoxically helps by dumping heat afterward. A cool room helps the drop.
- Cortisol — the alerting hormone; lowest around midnight, surging before wake (the cortisol awakening response). Evening stress/late screens keep it elevated and delay sleep.
Fundamentals
How much sleep you actually need
| Age | Recommended / 24 h |
|---|---|
| Newborn (0–3 mo) | 14–17 h |
| Infant (4–12 mo) | 12–16 h (incl. naps) |
| Toddler (1–2 yr) | 11–14 h |
| Preschool (3–5 yr) | 10–13 h |
| School age (6–12 yr) | 9–12 h |
| Teen (13–18 yr) | 8–10 h |
| Adult (18–60) | 7–9 h (≥7) |
| Older adult (65+) | 7–8 h |
AASM/SRS & AAP/AASM pediatric consensus. Individual need varies; ranges, not targets.
Do this
The Sleep Improvement Protocol (tick what you've adopted)
Ordered roughly by leverage. You don't need all of them — fix the top few first. Progress saves automatically on this device.
Anchor a fixed wake time — 7 days a week
The single most powerful lever. Your wake time, not your bedtime, sets the circadian clock. Pick one you can keep on weekends (±30 min) and let bedtime drift to when you're actually sleepy.
Get bright light early, dim light late
Get 10–30 minutes of outdoor light within an hour of waking (even overcast daylight is 10–100× brighter than indoor lighting). In the evening, dim overheads, switch to warm/low lamps, and avoid bright screens 2–3 h before bed.
Cut caffeine 8–10 hours before bed
With a ~5 h half-life, a 2 pm coffee still has a quarter of its caffeine working at 2 am. For an 11 pm bedtime, aim for last caffeine by ~1–3 pm; earlier if you're a slow metabolizer (sensitive to coffee, or carry slow CYP1A2).
No alcohol within 3–4 hours of bed
A nightcap is a trap: alcohol is sedating up front (you fall asleep fast) but as it metabolizes it fragments the second half of the night, suppresses early REM, worsens snoring/apnea, and triggers 3 am wake-ups. The "I slept but feel unrested" night is usually this.
Make the room cool, dark & quiet
Target ~18 °C / 65 °F. Block light with blackout curtains or a sleep mask (even dim light suppresses melatonin and reduces deep sleep). Mask noise with earplugs or a fan/white noise.
Keep a 30–60 min wind-down routine
A consistent low-stimulation buffer tells the brain sleep is coming: dim lights, shower, read a paper book, stretch, journal, or do a relaxation/breathing exercise. Same sequence nightly = a conditioned cue.
T-90 min : last food/alcohol; dim the lights; screens to night mode/low
T-60 min : warm shower or bath; set out tomorrow's clothes (offload worries)
T-45 min : phone on charger OUTSIDE the bedroom; analog alarm
T-30 min : read fiction / stretch / 10 slow breaths (4s in, 6s out)
T-0 : lights out at a consistent time; room cool & darkUse the bed only for sleep (and sex)
This is "stimulus control," the most evidence-backed piece of CBT-I. No working, scrolling, or worrying in bed — you want the brain to associate the bed with sleep, not with wakefulness.
Nap correctly — or not at all
If you nap: keep it 10–20 minutes, before ~3 pm. That refreshes alertness without entering deep sleep (which causes grogginess) and without stealing the sleep pressure you need at night. If you have insomnia, skip naps entirely — you need maximum sleep pressure at bedtime. See the nap guide.
Exercise — most days, not right before bed
Regular exercise deepens sleep and shortens the time to fall asleep; it's one of the few interventions that reliably increases slow-wave sleep. Morning/afternoon is ideal. Vigorous training in the last ~1–2 hours before bed raises core temp and adrenaline and delays sleep for some people — finish earlier, or test light evening movement (a walk, easy yoga) which is fine.
Stop big meals ~3 hours before bed
Large or fatty/spicy meals close to bedtime cause reflux and raise core temp, fragmenting sleep. Don't go to bed starving either — a small carb/protein snack (e.g. yogurt, banana, a few nuts) can help if hunger wakes you. Cap evening fluids to limit 3 am bathroom trips.
Offload a racing mind before bed
If thoughts spin at lights-out, do a "brain dump" earlier in the evening: write tomorrow's to-dos and worries on paper so the brain stops rehearsing them. In bed, use a non-striving technique — slow exhale-biased breathing, a body scan, or "cognitive shuffling" (picture random unrelated objects). The goal is to stop trying to sleep; effort backfires.
Give changes 2–4 weeks & track
Circadian habits take weeks to consolidate — don't judge a change after one bad night. Keep a simple sleep diary (or use a tracker as a trend tool, not a verdict).
Date | In bed | Lights out | Est. time to sleep | # wake-ups | Out of bed | Caffeine (last) | Alcohol | Exercise | Naps | Morning feel (1-5)
2026-06-28 | 22:45 | 23:00 | 15m | 1 | 06:45 | 13:30 | none | AM run | none | 4Working knowledge
Caffeine & alcohol — the dose/timing detail
A 2023 Sleep Medicine Reviews meta-analysis modeled how long before bed to stop, by dose. Earlier is safer if you're caffeine-sensitive:
| Caffeine source (approx.) | Dose | Stop at least … before bed |
|---|---|---|
| Espresso shot / small coffee | ~100 mg | ~4 hours |
| Standard mug of coffee | ~107 mg | ~9 hours |
| Large coffee / pre-workout | ~217 mg | ~13 hours |
| Energy drink (varies widely) | ~80–300 mg | read the label; treat like the column above |
Working knowledge
Supplements — what the evidence supports
| Supplement | Typical dose | Best for | Evidence & cautions |
|---|---|---|---|
| Melatonin | 0.5–1 mg (up to ~3 mg), 2–3 h before sleep | Jet lag, shift work, delayed sleep phase, age 55+ | Best evidence is for shifting timing, not sedation. Low dose works; higher doses can cause grogginess/vivid dreams. US supplements are unregulated — actual content varies wildly. Prolonged-release is first-line for insomnia in over-55s (per European guidance). |
| Magnesium glycinate | 200–400 mg elemental, evening | Mild insomnia, restless legs, if deficient | Meta-analysis (older adults): ~17 min faster sleep onset vs placebo, but low-quality evidence. Glycinate/bisglycinate is gentle on the gut; oxide is poorly absorbed and laxative. |
| Glycine | 3 g before bed | Subjective quality, faster onset | Small RCTs show improved sleep quality and next-day alertness, possibly via a mild core-temp drop. Generally well tolerated. |
| L-theanine | 100–200 mg | Pre-sleep anxiety, "wired" mind | Promotes calm without sedation; modest effect. Often paired with magnesium. Pairs well to blunt caffeine jitters earlier in the day. |
| Apigenin / chamomile | tea, or ~50 mg apigenin | Gentle relaxation, ritual | Mild; much of the benefit may be the warm-drink wind-down ritual. Chamomile is a ragweed-family allergen for some. |
| Ashwagandha | 300–600 mg (KSM-66/standardized) | Stress-driven poor sleep | Several RCTs show improved sleep and lower stress. Avoid in pregnancy, thyroid disorders, or with immunosuppressants; rare liver-injury reports. |
| Valerian | 300–600 mg extract | — | Popular but evidence is weak/inconsistent. Can interact with sedatives. |
| Avoid: diphenhydramine (Benadryl, ZzzQuil, "PM" pills) | — | Last resort only | Tolerance builds in days; anticholinergic side effects, next-day grogginess, and long-term use is associated with higher dementia risk in older adults. Not for routine sleep. |
Working knowledge
Naps — dose them like a tool
| Nap length | Effect | Use when |
|---|---|---|
| 10–20 min (power nap) | Alertness boost, no deep sleep, no grogginess. | Default. Early–mid afternoon dip. |
| ~30 min | Risk of waking mid-deep-sleep → groggy ("sleep inertia") for 15–30 min. | Generally avoid. |
| ~60 min | Includes deep sleep; aids memory but groggy on waking. | If memory consolidation > immediate alertness. |
| ~90 min (full cycle) | Complete cycle incl. REM; wake refreshed. | Big sleep debt, no night-sleep impact (e.g. weekend). |
Edge cases
Chronotype, jet lag & shift work
Chronotype — are you a lark or an owl?
Chronotype (your genetically-influenced natural timing) is real and partly fixed. Forcing an extreme owl onto a 5 am schedule creates chronic "social jet lag" and underperformance.
- To shift earlier (owl → earlier): bright light immediately on waking, dark/dim evenings, small early-evening melatonin (0.5 mg ~5–6 h before current sleep onset, under guidance), and move bedtime earlier in 15-min steps.
- Work with it where you can: schedule demanding work at your personal peak (late morning for most; later for owls). You can nudge a chronotype by an hour or two, not transform it.
Jet lag — pre-adapt and use light strategically
Rule of thumb: the body re-syncs ~1 time zone per day. Eastward travel (need to sleep earlier) is harder than westward.
- Shift your schedule 1 h/day toward the destination for a few days before flying.
- On arrival, adopt local meal & sleep times immediately; get morning light when going east, evening light when going west (the wrong light makes it worse).
- Low-dose melatonin (0.5–3 mg) at destination bedtime for east-bound trips can speed adaptation.
- Avoid alcohol and big meals in-flight; hydrate; nap only briefly.
Shift work — damage control
Night/rotating shifts fight biology and raise long-term health risks, so the goal is mitigation: keep a consistent sleep schedule even on days off where possible; use bright light during the shift and dark sunglasses on the commute home to avoid morning light resetting you; sleep in a blackout, cool, quiet room; strategic caffeine early in the shift (not the last few hours); a short pre-shift nap. Rotating forward (day→evening→night) is easier than backward.
Gold standard
CBT-I — first-line for chronic insomnia
Its components (several you've already met in the protocol above):
| Component | What it is |
|---|---|
| Stimulus control | Bed = sleep only; out of bed if awake >~20 min; fixed wake time. Re-associates bed with sleep. |
| Sleep restriction | Temporarily limit time in bed to actual sleep time to build sleep pressure and consolidate sleep, then expand. (Do this with guidance — it's counterintuitive and briefly tiring.) |
| Cognitive therapy | Challenge catastrophizing ("if I don't sleep I'll fail tomorrow"), which fuels the anxiety that prevents sleep. |
| Relaxation training | Diaphragmatic breathing, progressive muscle relaxation, body scan — lower pre-sleep arousal. |
| Sleep hygiene | The environmental/behavioral basics in this guide. Necessary but, alone, the weakest component — it rarely fixes real insomnia by itself. |
Working knowledge
Sleep trackers — useful trends, unreliable verdicts
Red flags — see a doctor
Sleep hygiene won't fix an underlying disorder. Seek evaluation if you have: