Poor Sleep Linked to Accelerated Brain Aging, Swedish Study Finds

New research suggests poor sleep may accelerate brain aging, with inflammation playing a key role — offering new hope that lifestyle changes could slow cognitive decline.

A landmark study conducted by researchers at the Karolinska Institutet in Sweden has found a strong link between poor sleep quality and accelerated brain aging, suggesting that even small disturbances in sleep could have long-term impacts on cognitive health. The findings, published in The Lancet eBioMedicine on September 30, build on growing evidence tying sleep health to the risk of neurodegeneration and dementia.

“Poor sleep may contribute to faster brain aging, and inflammation could be one of the key mechanisms behind this process,” said Dr. Abigail Dove, lead author and postdoctoral researcher at the Karolinska Institutet, in a statement accompanying the publication. “Since sleep is modifiable, improving sleep habits could be a practical way to slow brain aging.”

The Study: Sleep, Brain Scans, and Inflammation

The Swedish researchers used data from over 27,500 participants in the UK Biobank, with an average age of 54 and a gender split of 54% women. Participants self-reported their sleep habits, which were scored based on five key indicators: sleep duration, insomnia, snoring, daytime sleepiness, and chronotype (morning vs evening preference).

Based on this scoring system, individuals were categorized into three sleep groups:

• Healthy Sleep (≥ 4 points)
• Intermediate Sleep (2–3 points)
• Poor Sleep (≤ 1 point)

Approximately 8.9 years after the initial sleep assessment, participants underwent MRI scans. Using machine learning, the researchers analyzed 1,079 brain imaging markers to estimate each person’s “brain age” — a metric that compares the biological age of the brain to the individual’s actual age.

Notably, 285 MRI features had a particularly strong influence on the brain age estimation, including white matter structure and lesion presence.

Inflammation: A Hidden Culprit

To investigate potential mechanisms, the study also analyzed inflammatory biomarkers using an INFLA score, a composite of blood markers linked to systemic inflammation.

The results revealed a striking pattern: the worse the sleep quality, the greater the gap between chronological age and brain age. On average:

• Participants with intermediate sleep had brains 0.62 years older than their actual age.
• Those with poor sleep showed a brain age 0.99 years older.

Furthermore, for each point decrease in sleep score, the brain age gap widened by 0.48 years. Inflammation appeared to mediate up to 10.4% of the link between poor sleep and accelerated brain aging.

“This underscores that inflammation is a major mechanism connecting sleep to brain aging,” said Dr. Dove. “Though other biological systems, such as the glymphatic system — the brain’s waste clearance network — may also be involved.”

Sleep and the Dementia Connection

The findings add to a growing body of research suggesting poor sleep may increase the risk of dementia — though the direction of causality remains uncertain.

Is sleep disruption a cause of cognitive decline, or an early symptom of brain disease? The researchers acknowledged this ongoing debate and emphasized the importance of long-term studies like theirs to clarify the relationship.

A 2024 study of over 500 participants had previously shown that disrupted sleep in early midlife correlates with markers of brain aging in later life. The current study, however, significantly expands the evidence base using a much larger cohort and advanced neuroimaging analysis.

Study Limitations

The authors noted several limitations. Sleep patterns were self-reported, which may introduce bias. Additionally, participants in the UK Biobank tend to be healthier and wealthier than the general population, potentially limiting the generalizability of the findings.

Still, the use of machine learning models on large-scale MRI data adds scientific weight to the conclusions.

Sleep as a Modifiable Risk Factor

Perhaps the most hopeful aspect of the study is its focus on sleep as a modifiable behavior — unlike many other aging or genetic risk factors.

“Improving sleep quality may be a relatively accessible intervention to help delay brain aging,” said Dr. Dove. While further research is needed to test whether better sleep hygiene directly improves brain age, the current evidence offers a compelling reason for individuals and health systems to prioritize sleep health as part of dementia prevention strategies.

What Comes Next?

The Karolinska team hopes future research will explore whether improving sleep quality can actually reduce the brain age gap, and whether sleep-focused interventions could slow the progression of neurodegenerative diseases like Alzheimer’s.

As the science evolves, one thing remains clear: sleep is not just rest — it’s restoration, and increasingly, a cornerstone of brain health.