How much sleep do I actually need?

Most adults need 7-9 hours. There's a small minority of genuine short-sleepers who function on 6 — but they're rarer than people who claim to be them. If you're running on 5-6 hours and depending on caffeine to function, that's an under-sleeping pattern, not a special biology.

Is the time I fall asleep more important than how long I sleep?

Consistency of timing usually matters more than absolute bedtime. Holding the same wake time seven days a week is the single highest-leverage intervention for most adults; bedtime tends to drift in to match.

Does blue light from screens really matter?

Probably less than the alerting effect of the content. Reading a calm book on a dim Kindle for 30 minutes before bed is fine. Scrolling Twitter on full brightness while your nervous system fires up is the problem. The blue-light glasses industry has overplayed the spectral mechanism.

Should I track sleep with a wearable?

It's useful as a feedback tool, especially for catching trends, but treat the precise scores as approximate. Some users develop orthosomnia — anxiety about sleep scores that itself worsens sleep. If a tracker is stressing you out, take it off for a month.

What about supplements — melatonin, magnesium, ashwagandha?

Melatonin works as a circadian signal in small (0.3-0.5 mg) doses, especially for jet lag; the multi-milligram doses sold in shops are pharmacological. Magnesium glycinate helps a subset of people, especially if they're deficient. Ashwagandha has small effects in some trials. None substitute for fixing timing, light, caffeine, and environment first. Talk to a clinician before adding anything if you're on medication or pregnant.

I wake up at 3 am every night. Why?

Most common causes are alcohol metabolising and rebounding sympathetic activity (especially after evening drinking), high evening cortisol, blood sugar drops, hot bedrooms, or a partial sleep apnoea event. If it's persistent and unexplained, please see a clinician.

Sleep better

Consistency before everything

Pick a fixed wake time and hold it within 30 minutes seven days a week. This is the single most important intervention. The body's clock entrains to a regular wake time more strongly than to bedtime; once the wake time is stable, bedtime tends to follow.

The temptation is to sleep in on weekends. This is “social jet lag” — shifting your circadian phase by 1-3 hours every Friday and shifting it back on Monday. The cost is roughly equivalent to flying across timezones twice a week. For most adults, holding the weekend wake time within an hour of the weekday wake time is the highest-impact change they can make.

Light is the dominant signal

The suprachiasmatic nucleus (your body's master clock) is more influenced by light than by anything else. Two interventions:

Morning daylight. 10-15 minutes of outdoor light within 30 minutes of waking, ideally on most days. Indoor light (200-500 lux) is dim compared to overcast outdoor light (10,000+ lux). Going outside, even briefly, on a grey morning is more potent than sitting in a brightly lit kitchen.
Dim evenings. The hour before bed should be the dimmest hour of your day — warm bulbs, lamps not overheads, low screen brightness. The signal is roughly “the sun is going down,” and your body uses it to start producing melatonin.

Caffeine: dose and timing

Caffeine has a half-life of 5-7 hours in average adults, and longer in slow metabolisers (about 10-15% of people, by genotype). A 3 pm coffee can still have measurable plasma caffeine at 11 pm. Even when you fall asleep on schedule, residual caffeine reduces deep-sleep architecture and increases wake-after-sleep-onset events.

Practical rules:

Last caffeine at least 8 hours before bed. Earlier if you wake at night.
Tea is not innocent — strong black tea has caffeine doses comparable to coffee.
If you depend on afternoon caffeine to function, the underlying issue is usually total sleep volume, not the caffeine.

The bedroom

The bedroom is the input variable people invest in least and get the most leverage from. Walk it with the sleep environment audit. The high-leverage items:

Temperature. Cool. 16-19°C / 60-67°F suits most adults. Core body temperature needs to drop slightly to initiate sleep; an overheated room blocks the drop.
Darkness. Blackout where possible; remove or cover standby LEDs. Even moderate ambient light suppresses melatonin and slightly raises overnight heart rate.
Noise. Persistent noise (traffic, neighbours) fragments sleep even when you're not consciously aware. Earplugs or pink noise solve it for many people.
Bed. Old mattresses, wrong pillow firmness, and synthetic bedding that traps heat are the most common discomfort drivers. Fix one at a time.
No phone within reach. Charge the phone outside the bedroom. If you can't, keep it across the room. The intent isn't to demonise the device — it's to remove the reach-for-it loop at 3 am.

Wind-down

The 30-60 minutes before bed should be the calmest, dimmest part of your day. The point isn't a ritual aesthetic — it's lowering arousal so the transition into sleep doesn't require fighting a wired nervous system.

Things that work for most people: dim lights, no work, no news, no doomscrolling, warm shower, reading on paper or a dim e-reader, a short walk after dinner, light stretching. Things that fight you: bright overheads, intense exercise within 2 hours of bed, hard conversations, heavy meals after 9 pm.

Alcohol and other disruptors

Alcohol makes you fall asleep faster and stay asleep worse. The metabolic rebound (4-6 hours after drinking) reliably causes mid-night waking and reduces REM. Even modest doses (one or two drinks) measurably degrade sleep quality. This isn't moralising about drinking; it's the trade-off you're making when you have a glass of wine after dinner.

Heavy late meals, intense exercise close to bed, and emotional confrontations are similar — they raise sympathetic tone exactly when you want it falling. Move them earlier.

Common mistakes

Optimising supplements before fixing timing, light, caffeine, and environment.
Catching up on sleep at weekends and creating social jet lag.
Charging the phone next to the bed.
Drinking strong tea in the late afternoon and not counting it.
Working in bed; weakening the “bed = sleep” cue.
Treating wearable scores as ground truth.
Sleeping in a hot bedroom because the room feels “cosy.”

When to see a clinician

See a doctor if you snore loudly with daytime sleepiness (suspect sleep apnoea), if insomnia persists for more than three weeks despite reasonable basics, if you have new-onset early-morning waking with low mood, or if sleep problems track with restless legs, gasping awakenings, or significant weight changes.

Micro-course: The Sleep and Circadian Edge.
Tool: Sleep consistency tracker.
Worksheet: Sleep environment audit.
Path: Health Foundations for Busy Adults.