New Study Shows How Bad Sleep Could Be Ageing Your Brain Faster

A groundbreaking study conducted by researchers at the Karolinska Institute in Sweden has revealed a startling connection between poor sleep and accelerated brain ageing, with significant implications for cognitive health. Published on October 2, 2025, the study analyzed sleep behavior and brain MRI scans from over 27,000 UK adults aged 40 to 70, finding that individuals with poor sleep habits had brains that appeared nearly one year older than their chronological age. This accelerated brain ageing, driven by factors such as insomnia and irregular sleep patterns, could heighten the risk of cognitive decline, dementia, and even premature mortality, underscoring the critical role of sleep in maintaining brain health.

The study employed advanced brain imaging and machine learning to estimate brain age based on over 1,000 MRI markers, including brain tissue loss, cortical thinning, and blood vessel damage. By training a model on the healthiest participants—those with no major diseases and brains closely matching their actual age—researchers established a baseline for normal ageing.

When applied to the broader study population, the model revealed that individuals with poor sleep profiles, characterized by late chronotypes, abnormal sleep duration, insomnia, snoring, or excessive daytime sleepiness, exhibited significantly older-looking brains. Specifically, a one-point drop in a “healthy sleep score” correlated with a six-month increase in brain age gap, with late chronotypes and irregular sleep hours being the most significant contributors.

One key mechanism linking poor sleep to brain ageing is inflammation, which the study found accounts for approximately 10% of the connection. Poor sleep elevates inflammatory biomarkers in the body, which can damage blood vessels, accelerate brain cell death, and promote the buildup of toxic proteins, all of which harm brain health. Additionally, disrupted sleep impairs the glymphatic system, the brain’s waste-clearance network active during sleep, allowing harmful substances to accumulate. The study also suggests that poor sleep may exacerbate conditions like type 2 diabetes, obesity, and cardiovascular disease, which further contribute to neurological decline, compounding the risks over time.

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The findings highlight the importance of modifiable sleep habits in protecting brain health. Simple strategies, such as maintaining a consistent sleep schedule, limiting caffeine and screen time before bed, and creating a dark, quiet sleep environment, can significantly improve sleep quality. While not all sleep issues are easily resolved, these interventions offer a practical starting point for reducing the risk of accelerated brain ageing. The study’s comprehensive approach, leveraging a large sample size and multidimensional sleep metrics, strengthens its conclusions, building on prior research that linked poor sleep to cognitive decline and dementia.

As brain ageing is inevitable, lifestyle choices like prioritizing sleep can shape how it unfolds. The Karolinska study serves as a wake-up call, emphasizing that poor sleep is not just a nuisance but a measurable threat to brain health. By adopting healthier sleep practices, individuals may slow the biological ageing of their brains, potentially lowering the risk of neurological conditions and enhancing long-term cognitive vitality. As research continues to uncover the intricate links between sleep and brain function, making sleep a priority emerges as a critical step toward a healthier, sharper mind.

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