Analysis, People with a poor sleep profile had brains which appeared nearly one year older than expected based on their age, received 2025 10 30

[Colin Howard]

Greetings,

I wonder where I fint in this? How about you?

We spend nearly a third of our lives asleep, yet sleep is anything but
wasted time. Far from being passive downtime, it is an active and essential
process that helps restore the body and protect the brain. When sleep is
disrupted, the brain feels the consequences - sometimes in subtle ways that
accumulate over years.

In a new study, my colleagues and I examined sleep behaviour and detailed
brain MRI scan data in more than 27,000 UK adults between the ages of 40 and
70. We found that people with poor sleep had brains that appeared
significantly older than expected based on their actual age.

What does it mean for the brain to "look older"? While we all grow
chronologically older at the same pace, some people's biological clocks can
tick faster or slower than others. New advances in brain imaging and
artificial intelligence allow researchers to estimate a person's brain age
based on patterns in brain MRI scans, such as loss of brain tissue, thinning
of the cortex and damage to blood vessels.

In our study, brain age was estimated using over 1,000 different imaging
markers from MRI scans. We first trained a machine learning model on the
scans of the healthiest participants - people with no major diseases, whose
brains should closely match their chronological age. Once the model
"learned" what normal ageing looks like, we applied it to the full study
population.

Having a brain age higher than your actual age can be a signal of departure
from healthy ageing. Previous research has linked an older-appearing brain
to faster cognitive decline, greater dementia risk and even higher risk of
early death.

Sleep is complex, and no single measure can tell the whole story of a
person's sleep health. Our study, therefore, focused on five aspects of
sleep self-reported by the study participants: their chronotype ("morning"
or "evening" person), how many hours they typically sleep (seven to eight
hours is considered optimal), whether they experience insomnia, whether they
snore and whether they feel excessively sleepy during the day.

These characteristics can interact in synergistic ways. For example, someone
with frequent insomnia may also feel more daytime sleepiness, and having a
late chronotype may lead to shorter sleep duration. By integrating all five
characteristics into a "healthy sleep score", we captured a fuller picture
of overall sleep health.

People with four or five healthy traits had a "healthy" sleep profile, while
those with two to three had an "intermediate" profile, and those with zero
or one had a "poor" profile.

When we compared brain age across different sleep profiles, the differences
were clear. The gap between brain age and chronological age widened by about
six months for every one point decrease in healthy sleep score. On average,
people with a poor sleep profile had brains that appeared nearly one year
older than expected based on their chronological age, while those with a
healthy sleep profile showed no such gap.

We also considered the five sleep characteristics individually: late
chronotype and abnormal sleep duration stood out as the biggest contributors
to faster brain ageing.

A year may not sound like much, but in terms of brain health, it matters.
Even small accelerations in brain ageing can compound over time, potentially
increasing the risk of cognitive impairment, dementia and other neurological
conditions.

The good news is that sleep habits are modifiable. While not all sleep
problems are easily fixed, simple strategies: keeping a regular sleep
schedule; limiting caffeine, alcohol and screen use before bedtime; and
creating a dark and quiet sleep environment can improve sleep health and may
protect brain health.

How exactly does the quality of a person's sleep affect their brain health?

One explanation may be inflammation. Increasing evidence suggests that sleep
disturbances raise the level of inflammation in the body. In turn,
inflammation can harm the brain in several ways: damaging blood vessels,
triggering the buildup of toxic proteins and speeding up brain cell death.

We were able to investigate the role of inflammation thanks to blood samples
collected from participants at the beginning of the study. These samples
contain a wealth of information about different inflammatory biomarkers
circulating in the body. When we factored this into our analysis, we found
that inflammation levels accounted for about 10% of the connection between
sleep and brain ageing.

Other processes may also play a role

Another explanation centres on the glymphatic system - the brain's built-in
waste clearance network, which is mainly active during sleep. When sleep is
disrupted or insufficient, this system may not function properly, allowing
harmful substances to build up in the brain.

Yet another possibility is that poor sleep increases the risk of other
health conditions that are themselves damaging for brain health, including
type 2 diabetes, obesity and cardiovascular disease.

Our study is one of the largest and most comprehensive of its kind,
benefiting from a very large study population, a multidimensional measure of
sleep health, and a detailed estimation of brain age through thousands of
brain MRI features. Though previous research connected poor sleep to
cognitive decline and dementia, our study further demonstrated that poor
sleep is tied to a measurably older-looking brain, and inflammation might
explain this link.

Brain ageing cannot be avoided, but our behaviour and lifestyle choices can
shape how it unfolds. The implications of our research are clear: to keep
the brain healthier for longer, it is important to make sleep a priority.

Abigail Dove is a Postdoctoral Researcher in Neuroepidemiology at Karolinska
Institute.

This article was originally published by The Conversation.

RTÉ Lifestyle.

Colin Howard, Southern England.