Trouble sleeping? It could raise your dementia risk by 40 per cent
Two new studies highlight how chronic sleep problems may affect brain health over time, potentially increasing the risk of dementia.
A Swedish study, published in the journal eBioMedicine, analysed MRI scans from 27,500 middle-aged and older adults. Using machine learning, researchers estimated each participant's brain age based on over a thousand brain MRI phenotypes.
How was the study conducted?
Sleep quality was assessed using five self-reported habits: being a morning or evening person, sleep duration, insomnia, snoring and daytime sleepiness. Poor sleep quality was associated with brains appearing, on average, one year older than the individual's actual age. For every one-point drop in the healthy sleep score, brain age advanced by approximately six months. Notably, the association was significantly stronger in men than in women.
Inflammation appeared to account for about 10 per cent of the link between poor sleep and accelerated brain ageing. Researchers also pointed to other possible mechanisms, including disruptions in the brain’s waste clearance system, which primarily happens during sleep, and the impact of poor sleep on cardiovascular health.
Meanwhile, a US study published in the journal Neurology followed 2,750 cognitively healthy seniors for over five years. The findings showed that chronic insomnia (trouble sleeping at least three days a week for three months or more) was associated with a 40 per cent increased risk of developing dementia or experiencing cognitive decline, which is the equivalent of 3.5 additional years of ageing.
Participants with persistent sleep issues experienced faster declines in memory and thinking skills, had lower cognitive test scores and greater accumulation of amyloid plaques and brain tissue damage—both key indicators of Alzheimer’s disease. Those with a genetic predisposition to Alzheimer’s (carrying the ApoE4 gene) saw even more rapid cognitive decline.
“This reinforces the importance of treating chronic insomnia—not just to improve sleep quality but potentially to protect brain health as we age,” said the lead researcher. “Our results also add to a growing body of evidence that sleep is not just about rest—it is also about brain resilience.”
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