Is 8 Hours of Sleep Really Necessary? New Research on REM, Deep Sleep and Disease Risk

Most of us have heard that we should aim for around eight hours of sleep each night.

But new research suggests that how we sleep may be just as important as how long we sleep.

A large study published in PLOS Medicine on 17 September 2026 analysed sleep patterns from more than 95,000 UK Biobank participants and explored how different aspects of sleep were associated with future health.

Researchers looked beyond simply counting hours asleep. They examined REM sleep, deep sleep, sleep regularity and the amount of time people spent awake after initially falling asleep.

So, does everyone really need exactly eight hours?

Not necessarily.

What did the new sleep study find?

Researchers analysed wrist-worn accelerometer data from 95,559 middle-aged and older adults.

Using a validated machine-learning algorithm, they estimated:

REM sleep
light and deep sleep
total sleep duration
sleep irregularity
wakefulness after initially falling asleep.

Participants were followed for a median of 8.9 years, allowing researchers to compare sleep patterns with more than 1,000 subsequent health outcomes.

The overall message was that sleep architecture, sleep duration and sleep consistency all appeared to matter.

Why are REM and deep sleep important?

REM sleep is the stage most associated with dreaming and has important roles in memory, learning and emotional processing.

Deep sleep is particularly important for physical recovery and restoration.

In the study, greater amounts of REM and deep sleep were associated with lower incidence of several health conditions.

However, that does not mean that increasing REM or deep sleep will necessarily prevent disease.

This was an observational study, so it can identify associations but cannot prove cause and effect.

Is six to eight hours enough?

Across many of the conditions studied, sleeping around six to eight hours was associated with more favourable health patterns, while very short sleep was generally associated with poorer outcomes.

That doesn't mean everyone should aim for six hours.

Individual sleep needs vary considerably, and some people naturally need more sleep than others.

The more important message is that consistently very short, fragmented or irregular sleep may be a sign worth paying attention to.

What about waking repeatedly during the night?

The researchers also measured wakefulness after sleep onset, essentially, how much time somebody spends awake after initially falling asleep.

This is particularly relevant to insomnia.

Insomnia does not always mean being unable to fall asleep.

Some people:

struggle to fall asleep
wake repeatedly during the night
wake very early and cannot return to sleep
sleep at inconsistent times
spend enough hours in bed but still feel exhausted during the day.

Persistent sleep disruption that affects daytime concentration, mood, energy or functioning may therefore deserve more attention than simply trying to achieve a particular number of hours.

Does poor sleep cause these diseases?

Not necessarily.

The study was observational, meaning researchers cannot determine whether disturbed sleep contributed to later illness, whether developing health conditions affected sleep, or whether other factors influenced both.

Sleep stages were also estimated using wrist accelerometers and machine learning rather than overnight polysomnography, which remains the clinical gold standard for assessing sleep stages.

So claims such as “lack of REM sleep causes dementia” or “eight hours prevents disease” would go beyond what this research can demonstrate.

What if better sleep habits aren't enough?

Good sleep habits remain an important starting point.

However, some people continue to experience insomnia despite improving their sleep routine and trying evidence-based approaches such as cognitive behavioural therapy for insomnia (CBT-I).

When insomnia has persisted for months and is significantly affecting daytime functioning, it may be appropriate to consider a clinical assessment rather than simply accepting poor sleep as normal.

For eligible adults, prescription treatment may sometimes be considered.

One option is daridorexant, also known as Quviviq, which belongs to a newer class of medicines called dual orexin receptor antagonists.

Rather than working in the same way as traditional sedative medicines, daridorexant blocks orexin receptors involved in promoting wakefulness, thereby reducing the drive to remain awake.

NICE recommends daridorexant for adults whose insomnia occurs at least three nights per week for at least three months and considerably affects daytime functioning, where CBT-I has either been tried without sufficient benefit, is unavailable or is unsuitable.

It is not suitable for everyone, and treatment should only follow an appropriate clinical assessment.

NICE recommends reviewing treatment within three months and periodically thereafter to ensure it remains appropriate and effective.

How Pharmulous can help

At Pharmulous, insomnia is assessed as a clinical condition rather than simply treating the number of hours somebody sleeps.

Our clinicians consider:

how long your sleep problems have been present
whether you struggle to fall asleep, stay asleep or both
how your sleep affects daytime functioning
previous treatments, including CBT-I
other medical conditions
other medicines you take
whether another sleep disorder or underlying cause may need investigation.

The aim is not simply to make somebody sleep for eight hours.

It is to work towards more consistent, restorative sleep and better daytime functioning, using the safest and most appropriate approach for the individual.