Poor sleep accelerates brain ageing and making it appear older than it actually is, researchers have found.
Sleep helps to restore the body and protect the brain and when it is disrupted the brain can feel the consequences – with research linking an ageing brain to cognitive decline and increased dementia risk.
Poor sleep has already been linked to dementia, but experts say it is unclear if unhealthy sleep habits contribute to the development of dementia or if these sleep habits are an early symptom of the degenerative brain condition.
Researchers at the Karolinska Institutet in Sweden examined sleep behaviour and MRI scans in more than 27,000 UK adults between the ages of 40 and 70 and found people with poor sleep had brains that appeared significantly older than their actual age.
The brain imaging study published in the journal eBioMedicine used machine learning on the scans of the healthiest participants who had no major diseases and once the model understood what normal ageing looked like, it was applied to the data.
The participant’s sleep quality was scored on five self-reported factors: chronotype (being a morning/evening person), sleep duration, insomnia, snoring, and daytime sleepiness. They were then divided into three groups depending on their score: healthy (≥4 points), intermediate (2-3 points), or poor (≤1 point) sleep.
“The gap between brain age and chronological age widened by about six months for every 1-point decrease in healthy sleep score,” said Dr Abigail Dove, researcher at the Department of Neurobiology, Care Sciences and Society at the Karolinska Institutet, who led the study.
“People with poor sleep had brains that appeared on average one year older than their actual age,” she added.
Researchers suggested increased levels of inflammation could partly explain the association with sleep and brain ageing.
There is increasing evidence to suggest a lack of sleep raises inflammation in the body, which can in turn harm the brain by damaging blood vessels, triggering the buildup of toxic proteins and speeding up brain cell death.
Blood samples taken at the start of the study revealed inflammation levels accounted for 10 per cent of the connection between sleep and brain ageing.
“Our findings provide evidence that poor sleep may contribute to accelerated brain ageing and point to inflammation as one of the underlying mechanisms,” said Dr Dove.
“Since sleep is modifiable, it may be possible to prevent accelerated brain ageing and perhaps even cognitive decline through healthier sleep,” she added.
Another possible explanation for brain ageing after consistent poor sleep is the negative effects it has on the brain’s built-in waste clearance system which is mainly active during sleep.
When sleep is disrupted or insufficient this mechanism may not function properly, allowing harmful substances to build up in the brain.
Researchers also suggested poor sleep affects cardiovascular health, which in turn can have a negative impact on the brain as a poor blood supply can starve brain cells of oxygen and nutrients.
