Sleep, honestly — what actually works

Sleep is the foundation everything else rests on. The honest headline: the behaviours matter far more than any pill or gadget — but there is real nuance on the supplements, so here is what the evidence actually supports.

Why sleep is the foundation

Sleep supports memory, cognition, immune and endocrine regulation. Brain-fluid dynamics and waste clearance also change during sleep, although their clinical importance in humans is still being worked out. In observational studies, both short and long sleep are associated with higher mortality, with roughly seven hours near the lowest observed risk; this association does not prove that sleep duration alone causes the difference.

No supplement fixes a bad sleep environment or an erratic schedule. Get the behaviours right first; treat supplements as small, optional add-ons, not the main lever.

What happens across the night

What happens across the night — an illustrative chart on this page. Figures use honest, cited or clearly-illustrative data; they are visual aids, not personal measurements.

The stages, and why they matter

A night is not one flat state: non-REM and REM sleep alternate in cycles averaging roughly 90 minutes, with substantial variation. N1 and N2 make up much of the night. Slow-wave sleep (N3) is concentrated earlier and is associated with the largest sleep-related growth-hormone pulse and important memory processes. REM periods usually lengthen later in the sleep episode and contribute to memory and emotional processing, although no stage has one exclusive function.

The practical takeaway is that an adequate, uninterrupted sleep opportunity protects the full sequence. Cutting the final hours disproportionately reduces later REM-rich sleep; shortening sleep at either end still reduces total sleep. Circadian timing and light exposure affect when this architecture occurs, while alcohol can alter and fragment it.

Sleep duration and risk

Sleep duration and risk — an illustrative chart on this page. Figures use honest, cited or clearly-illustrative data; they are visual aids, not personal measurements.

Rule this out first: sleep apnoea

Before optimising anything, rule out the most common hidden sleep disorder. In obstructive sleep apnoea (OSA) the airway repeatedly collapses during sleep, briefly stopping your breathing — sometimes hundreds of times a night — without you ever remembering waking. You just wake exhausted and never know why.

A 2019 literature-based model estimated that 936 million adults aged 30–69 worldwide could meet the threshold for at least mild OSA, including about 425 million with moderate-to-severe OSA. These are modelled prevalence estimates, not diagnosed case counts. Earlier literature also suggested that a large majority of clinically important cases remained undiagnosed.

The biggest reason people miss it: the myth that apnoea only affects heavily overweight men. Obesity is a major risk factor, but plenty of lean, fit people and women have it too — driven by jaw and airway shape, age, and menopause. Because they "don’t look the type", they and their doctors don’t think of it.

How much apnoea goes unseen

How much apnoea goes unseen — an illustrative chart on this page. Figures use honest, cited or clearly-illustrative data; they are visual aids, not personal measurements.

When to get checked for apnoea

Take these seriously — apnoea is very treatable once found.

• Exhausted for no reason you can explain — If you feel unrefreshed and tired through the day no matter how long you spend in bed, and the usual fixes don’t help, apnoea is a leading hidden cause worth ruling out — not just "poor sleep hygiene". (note)
• Your partner has noticed it — Loud snoring, gasping or choking, or actually seeing you stop breathing and then restart, are the classic signs — often a bed partner notices the pauses long before you do. Take that observation seriously. (note)
• It is not only a disease of obesity — OSA is common in normal-weight and fit people too, where facial and airway anatomy, age, male sex or menopause drive it. Being slim does not rule it out — this myth is exactly why so many go undiagnosed. (note)
• The next step is simple — Raise it with your GP, who can arrange a sleep study — an at-home test or an overnight sleep-lab recording — that measures how often your breathing drops per hour (the AHI). Untreated OSA raises the risk of high blood pressure, heart disease, stroke and accidents; treated (often with CPAP), many people feel transformed. (note)

What actually works — behaviour first

The high-leverage, well-supported basics.

• Keep a consistent sleep and wake time — Regularity may matter as much as duration. A steady rhythm — including weekends — is one of the strongest, cheapest levers. (established)
• Morning daylight, dim evenings — Bright light early anchors your body clock; dim, warm light at night lets melatonin rise naturally. This is the real "melatonin" lever — your own. (established)
• Cool, dark, quiet room — A slightly cool bedroom, blackout and low noise measurably improve sleep depth and continuity. (established)
• Cut caffeine 8–10 hours before bed — Afternoon caffeine quietly erodes deep sleep even if you fall asleep fine. Individual metabolism varies — slow metabolisers should stop earlier. (established)
• Don’t use alcohol as a sleep aid — It helps you fall asleep but fragments the second half of the night and suppresses REM — you sleep worse, not better. (established)
• A wind-down routine; screens down — A consistent pre-sleep buffer (reading, breathing, a warm shower) helps most people; the "blue light" effect is smaller than the stimulation/late-night-scrolling effect. (emerging)

Supplements — what’s proven vs not

Honestly rated. Most are minor; none replace the basics.

• Melatonin — Melatonin is a circadian timing signal with evidence for jet lag and delayed sleep-wake timing; meta-analyses also find modest average improvements in sleep onset for some sleep disorders. Dose and timing depend on the purpose, and current evidence does not support one universally optimal low dose. More is not automatically better and can add next-day effects. Short-term use is generally well tolerated; multi-year nightly use is less well studied. (emerging)
• Magnesium (glycinate) — Helps if your intake is low; gentle on the gut. Benefits are clearest when you were deficient to begin with — it is not a strong sedative for everyone. (emerging)
• Glycine (~3 g before bed) — Small trials suggest better subjective sleep quality and next-day alertness. Safe and cheap; the effect is real but modest and the evidence is early. (emerging)
• L-theanine — Promotes calm rather than sedation; may help anxious pre-sleep arousal, often paired with (or replacing) late caffeine. Modest. (emerging)
• Ashwagandha — Short trials show modest stress reduction and small sleep improvements. Promising but small, short and variable in product quality. (emerging)
• Valerian — Popular and traditional, but trials are inconsistent and product quality varies widely. Do not count on it. (hype)
• CBD, “sleep gummies”, high-dose melatonin stacks — Largely oversold for healthy sleepers. High-dose melatonin is not better (more grogginess, no more benefit), and many gummies are under- or over-dosed. Spend on the basics, not the stack. (hype)
• Prescription hypnotics (Z-drugs, benzodiazepines) — Effective short-term but carry tolerance, dependence and next-day impairment. A clinician decision for a specific problem — not a supplement, and not a long-term sleep strategy. (note)

What’s oversold

• Buying a fix from a tracker or gadget — Measuring sleep is not improving it — and fixating on scores can cause "orthosomnia", anxiety that actually worsens sleep. Use trackers as a loose signal, not a verdict. (hype)

What we still don’t know

• Is nightly melatonin safe long-term? Short-term use is well tolerated, but multi-year nightly use has limited safety data. Use the lowest effective dose and revisit the need.
• Does sleep tracking actually improve sleep? It raises awareness, but there is little evidence that wearing a tracker makes you sleep better — and for some it makes things worse.
• Who responds to which supplement? Response to magnesium, glycine or theanine varies a lot between people and we can’t yet predict it. Trial one at a time.

Key terms

• Circadian rhythm Your ~24-hour body clock, set mainly by light, that governs when you feel sleepy and alert.
• Melatonin The hormone your brain releases at night to signal "time to sleep" — a timing cue, not a sedative.
• Sleep hygiene The behaviours and environment that support good sleep (schedule, light, temperature, caffeine timing).
• Orthosomnia Anxiety driven by chasing a perfect sleep-tracker score, which can itself worsen sleep.
• Sleep apnoea A common, often-undiagnosed disorder where the airway repeatedly collapses in sleep, pausing breathing and fragmenting rest.
• AHI Apnoea–hypopnoea index — how many times per hour breathing stops or shrinks during sleep; the main severity score for apnoea.
• CPAP Continuous positive airway pressure — a bedside machine and mask that keeps the airway open; the main treatment for moderate-to-severe apnoea.