Sleep and Longevity: The Habit That Holds Up Everything Else

Sleep is the habit that holds up everything else in longevity medicine. When it slips, your training, appetite, mood and blood pressure tend to slip with it.

On 13 October the American Academy of Sleep Medicine released a Stanford study suggesting a consumer smartwatch can help screen for moderate to severe obstructive sleep apnoea. The watch picked up 94% of people who had it. That is a real step forward. It is also a good moment to be precise about what a watch can and cannot tell you about your sleep.

Let me set out where I stand. I track my own sleep, and patients often bring me their wearable data. The data is useful. It is also easy to misread, and the device on your wrist is not a sleep study. This article covers why sleep matters for how long and how well you live, what the new smartwatch research actually found, how sleep apnoea is diagnosed in Australia, and which sleep supplements are worth your money.

Does sleep affect how long you live?

The best data we have says yes, and regularity matters as much as hours.

In 2023, researchers led by Daniel Windred published a UK Biobank study in the journal Sleep. They tracked 60,977 adults who wore a wrist accelerometer for a week, then followed them for an average of six years. Compared with the least regular sleepers, people with more regular sleep had a 20% to 48% lower risk of dying from any cause. Their risk of dying from heart and metabolic disease was 22% to 57% lower. Regularity was a stronger predictor of death than sleep duration.

The brain tells a similar story. The Whitehall II study, published in Nature Communications in 2021, followed 7,959 British adults for more than 25 years. People who regularly slept six hours or less in their 50s and 60s were about 30% more likely to develop dementia than those sleeping seven hours. The researchers were careful to say this shows an association, not cause.

That caveat matters. Poor sleep can be an early sign of disease as well as a cause of it. So I grade it this way. The link between sleep and long term health is established. The idea that fixing your sleep will add years to your life is promising, but not yet proven by trials. It fits with my earlier article on dementia risk, where I rated sleep quality and treating sleep apnoea as promising.

How much sleep do adults need?

Seven hours or more, most nights. That is the consensus of the American Academy of Sleep Medicine and the Sleep Research Society, published in 2015.

Many Australians fall short. The Sleep Health Foundation's national survey of 1,011 adults found 33% to 45% reported poor or short sleep with daytime effects. One in five reported significant insomnia. 29% said they drive drowsy at least once a month.

Three things count, and a watch only measures some of them well:

• Duration: total time asleep, not time in bed.

• Regularity: going to bed and getting up at similar times, weekends included.

• Quality: how often you wake, how refreshed you feel, and whether your breathing is disrupted.

Of the three, regularity is the one people underrate. The National Sleep Foundation's 2023 consensus statement, published in Sleep Health, linked regular bed and wake times with better heart, metabolic and mental health, and named a regular wake time as the most practical place to start. Hours still matter. But consistency matters as much, and in the UK Biobank data it predicted mortality more strongly.

Summer adds a fourth problem. The Lancet Countdown on Health and Climate Change, released on 28 October, estimated that hotter nights cost Australians an average of 34 hours of sleep a year between 2021 and 2025. A cool, dark bedroom is not a luxury in a Sydney January.

Can a smartwatch detect sleep apnoea?

It can flag it. It cannot diagnose it.

The study behind the October news was published in the Journal of Clinical Sleep Medicine. Stanford researchers asked 147 adults, average age 54, to wear a commercially available smartwatch for two nights during a lab sleep study and three nights at home. Every participant had already been diagnosed with moderate to severe sleep apnoea, or was judged likely to have it.

The watch's sleep apnoea feature picked up 94% of people with moderate to severe disease. That is its sensitivity. Its specificity was 67%, which means about one in three people without the condition were flagged anyway.

Three details matter when you read the headlines:

• The group was chosen because they were likely to have sleep apnoea. A watch tends to look more accurate in that setting than it will across the general public.

• The watch manufacturer funded the study and supplied the devices.

• The principal investigator, Dr Robson Capasso, said it plainly: "These devices are not diagnostic." Their job is to shorten the path to a proper assessment.

The TGA reached the same position in May 2025, when it approved sleep apnoea notification features on two major smartwatch brands. Both are designed to alert you to possible signs. Neither is intended to diagnose.

What wearables measure well, and what they don't

Consumer devices are good at telling when you are asleep. They are weaker at telling when you are awake, and at sleep stages. A 2021 study in Sleep tested seven consumer trackers against laboratory polysomnography. All detected sleep well. None reliably detected wake, and they tended to overestimate light sleep. Your "deep sleep" score is an estimate.

There is a downside to watching the numbers too closely. In 2017, Kelly Baron and colleagues at Rush University described patients who became so anxious about their tracker scores that their sleep got worse. They called it orthosomnia. Some spent longer in bed to push the number up, which is the opposite of what treatment for insomnia advises.

My approach is simple. I use the trends over weeks, not the score from last night. Mostly I look at consistency: are my bedtime and wake time steady across the week? That is the measure with the best science behind it, and it is the one a watch records well.

One feature I ignore is the sleep debt prompt. After a late night with work or family, my watch will suggest going to bed an hour earlier, at 9.30 instead of my usual 10.30. The body clock does not cooperate. Sleep researchers call the two to three hours before your usual bedtime the forbidden zone, or wake maintenance zone, when your circadian rhythm pushes you to stay alert. Peretz Lavie first described it in 1986, and a 2024 study in Frontiers in Sleep confirmed it in adults. Going to bed an hour early often means lying awake. A better plan is to keep your usual wake time, go to bed when you are sleepy, and let the extra sleep pressure deepen the next night. The National Sleep Foundation also says an extra hour or two on a day off helps most people recover from a short week.

Sleep apnoea in Australia: how common, and how it is diagnosed

Obstructive sleep apnoea is common and mostly missed. A 2019 analysis in The Lancet Respiratory Medicine estimated 936 million adults aged 30 to 69 have it worldwide, and 425 million have moderate to severe disease.

In Australia, only 8% of adults in the Sleep Health Foundation survey reported a diagnosis. The real figure is far higher. In the Men Androgen Inflammation Lifestyle Environment and Stress study in Adelaide, researchers ran home sleep studies on 837 men aged 40 and over who had never been diagnosed. About one in four had moderate or severe sleep apnoea.

It matters for longevity because untreated sleep apnoea strains the whole system. The same Adelaide group found undiagnosed severe sleep apnoea was linked to about double the odds of depressive symptoms. And as I covered in my dementia article, poor sleep and untreated sleep apnoea are associated with cognitive decline.

How to get tested

You do not need a smartwatch alert to ask. Signs worth raising with your GP include loud snoring, waking unrefreshed, daytime sleepiness, and a partner who has seen you stop breathing at night.

Since November 2018, a GP can refer you directly for a Medicare subsidised home sleep study if validated questionnaires, such as the Epworth Sleepiness Scale and STOP-Bang, show a high likelihood of moderate to severe sleep apnoea. More complex cases go to a sleep or respiratory physician, who may arrange an overnight study in a sleep lab.

If you are diagnosed, treatment is matched to severity. Options include CPAP, a custom mouthguard made by a dentist that holds the jaw forward, positional therapy, and weight loss. A sleep physician or your GP can talk you through which suits you.

Diagnosis is the easier part

Getting tested is easier than it used to be. Living with the treatment is harder. CPAP works when it is worn, and many people struggle to wear it.

A 2016 review by Brian Rotenberg and colleagues pooled 20 years of CPAP studies. About a third of patients were not using it enough, and average use was 4.6 hours a night. That figure has barely improved since the early 2000s. About one in ten people in the trials could not tolerate CPAP at all.

The reasons are human. A mask on your face all night. A dry mouth or a blocked nose. The hum of the machine, and a hose that pulls when you roll over. Claustrophobia for some people, cost and travel for others, and for many, plain fatigue with the routine.

So a diagnosis is only the start. Good follow up makes the difference: the right mask, adjusted settings, and a regular look at the machine's usage data with your doctor. If CPAP is not working for you, say so. A mouthguard, positional therapy or weight loss may suit you better, and a sleep physician can talk you through the options.

What actually improves sleep

The basics are unglamorous and they work. In my practice, these are the ones that move the needle most often:

• Get up at the same time every day, including weekends. Regular wake time anchors everything else.

• Get outdoor light in the morning, and keep the evening dim.

• Keep the bedroom cool and dark, which matters more as summer arrives.

• Finish hard training a few hours before bed where you can. My Hyrox session is late on Thursdays, and I notice the strain and adrenaline in my sleep and recovery that night.

• Cut alcohol late in the evening. It helps you fall asleep, then fragments the second half of the night.

If you have insomnia, the first treatment is not a pill

Cognitive behavioural therapy for insomnia, known as CBT-I, is the recommended first treatment. The Australasian Sleep Association, the American Academy of Sleep Medicine and the European Sleep Research Society all say so. A 2019 review in the Australian Journal of General Practice found CBT-I works about as well as sleeping tablets in the short term, and its benefits last for up to three years after treatment ends.

CBT-I is more than sleep hygiene. Its two strongest parts are stimulus control, which retrains your brain to link bed with sleep, and sleep restriction, which briefly limits time in bed so sleep becomes deeper and more consolidated. Sleep restriction needs supervision, especially if you might have sleep apnoea. CBT-I can be delivered face to face, or through online programs with good trial evidence. In Australia, sessions with a psychologist can be covered under a mental health care plan from your GP.

Do sleep supplements work?

Some help a little. None replaces the basics.

Magnesium, and does the form matter?

Magnesium is one of the most popular sleep supplements. The evidence is real but modest.

A 2021 meta-analysis in BMC Complementary Medicine and Therapies pooled three small trials in 151 older adults. Magnesium helped people fall asleep about 17 minutes faster than placebo. Total sleep time did not change significantly, and the authors rated the evidence low to very low quality.

Two newer trials looked at specific forms. In 2025, a trial in Nature and Science of Sleep gave 155 adults with poor sleep 250 mg of elemental magnesium as bisglycinate, or placebo, for four weeks. Insomnia scores improved slightly more with magnesium. The effect was small, and it was larger in people who ate less magnesium to begin with. In 2024, a trial in Sleep Medicine X gave 80 adults magnesium L-threonate or placebo for 21 days and reported better sleep scores, partly measured with a consumer sleep ring.

My read: there is no strong evidence that one form beats another for sleep. The people most likely to benefit are those whose diet is low in magnesium. Leafy greens, nuts, seeds, legumes and whole grains come first.

Melatonin is a medicine in Australia

Melatonin is sold as a supplement in the United States. In Australia it is a regulated medicine. Most melatonin needs a prescription, and a pharmacist can supply it without one only in narrow circumstances. Your doctor or pharmacist can tell you whether it suits you.

That matters if you buy gummies online from overseas. A 2023 study in JAMA tested 25 melatonin gummy products sold in the US. Actual content ranged from 74% to 347% of the labelled amount. Only three were within 10% of the label.

How the common options grade

What this means for you

Sleep is one of the few longevity tools that costs nothing and touches everything. Aim for seven hours or more, keep your wake time steady, and keep the bedroom cool as summer arrives.

Use your watch for trends, and as a prompt. If it flags possible sleep apnoea, or you snore and wake tired, see your GP and ask about a sleep study. If you have insomnia, ask about CBT-I before reaching for a supplement. Magnesium may help a little, especially if your diet is low in it.

If you want to see how your sleep fits with your bloods, training and long term risk, an initial consultation is a good place to start.

FAQ

Can my smartwatch diagnose sleep apnoea?

No. It can flag possible signs. The TGA approved these features for notification, not diagnosis. A sleep study confirms it.

Is magnesium glycinate better than other forms for sleep?

Not proven. Small trials of glycinate and L-threonate show modest benefits, but no trial has shown one form clearly beats another.

Can I buy melatonin over the counter in Australia?

Mostly no. Melatonin is a regulated medicine here. A pharmacist can supply it without a prescription only in narrow circumstances, so ask your doctor or pharmacist.

Is sleeping in on weekends enough to catch up?

Partly. The National Sleep Foundation says an extra hour or two on a day off helps most people recover from a short week. But a big-lie in shifts your body clock, and regular timing predicted lower mortality more strongly than hours in the UK Biobank data. Keep the lie-in modest.

General information, not individual medical advice. Speak to your own doctor.

References

• Alavi A et al. Smartwatch-based detection of moderate-to-severe and high-risk obstructive sleep apnea. J Clin Sleep Med. 2026.

• Windred DP et al. Sleep regularity is a stronger predictor of mortality risk than sleep duration: a prospective cohort study. Sleep. 2023.

• Sabia S et al. Association of sleep duration in middle and old age with incidence of dementia. Nat Commun. 2021.

• Watson NF et al. Recommended amount of sleep for a healthy adult: a joint consensus statement of the American Academy of Sleep Medicine and Sleep Research Society. Sleep. 2015.

• Adams RJ et al. Sleep health of Australian adults in 2016: results of the 2016 Sleep Health Foundation national survey. Sleep Health. 2017.

• Sletten TL et al. The importance of sleep regularity: a consensus statement of the National Sleep Foundation sleep timing and variability panel. Sleep Health. 2023.

• Lancet Countdown on Health and Climate Change. 2026 report. Accessed October 2026.

• Chinoy ED et al. Performance of seven consumer sleep-tracking devices compared with polysomnography. Sleep. 2021.

• Baron KG et al. Orthosomnia: are some patients taking the quantified self too far? J Clin Sleep Med. 2017.

• Lavie P. Ultrashort sleep-waking schedule. III. Gates and forbidden zones for sleep. Electroencephalogr Clin Neurophysiol. 1986.

• Monterastelli A et al. The forbidden zone for sleep is more robust in adolescents compared to adults. Front Sleep. 2024.

• Benjafield AV et al. Estimation of the global prevalence and burden of obstructive sleep apnoea: a literature-based analysis. Lancet Respir Med. 2019.

• Lang CJ et al. Associations of undiagnosed obstructive sleep apnea and excessive daytime sleepiness with depression: an Australian population study. J Clin Sleep Med. 2017.

• Rotenberg BW et al. Trends in CPAP adherence over twenty years of data collection: a flattened curve. J Otolaryngol Head Neck Surg. 2016.

• Grima NA et al. Insomnia management. Aust J Gen Pract. 2019.

• Mah J, Pitre T. Oral magnesium supplementation for insomnia in older adults: a systematic review and meta-analysis. BMC Complement Med Ther. 2021.

• Schuster J et al. Magnesium bisglycinate supplementation in healthy adults reporting poor sleep: a randomized, placebo-controlled trial. Nat Sci Sleep. 2025.

• Hausenblas HA et al. Magnesium-L-threonate improves sleep quality and daytime functioning in adults with self-reported sleep problems: a randomized controlled trial. Sleep Med X. 2024.

• Lelak K et al. Quantity of melatonin and CBD in melatonin gummies sold in the US. JAMA. 2023.