We all know that sleep is tied to short-term behavioral things like mood and productivity, but a new study is tying poor sleep quality to accelerated brain aging (i.e., dementia and general cognitive decline) over the long-term.

In the study, Swedish investigators analyzed data from 27,500 participants (mean age of 54 years; 54% female) from the UK. Using self-reported surveys that focused on sleep length, insomnia, snoring, and daytime sleepiness, the researchers gave each participant a sleep score and grouped them into three categories: 41.2% were “healthy” sleepers (≥ 4 points); 55.6% were “intermediate” sleepers (2-3 points); and 3.3% were “poor” sleepers (≤ 1 point).

About 9 years after baseline assessment, participants underwent brain MRI. Brain age was then assessed using machine learning based on 1,079 markers, including the number of lesions in specific brain regions and the microstructure of certain white-matter tracts. 

The results.

For every point decrease in sleep score, the gap between brain age and the person’s actual age grew one-half of a year. 

This gap between actual age and brain age occurred over a ~9-year period, suggesting the gap would widen further over time, although this would need further study.

Participants with intermediate or poor sleep were more likely to be male, to be older, to have a higher body mass index (BMI), and to have a lower socioeconomic status. 

Inflammation is thought to be a primary mechanism linking sleep to brain aging, and the glymphatic system, the brain’s waste-disposal system, is also thought to play a role.

“Sleep is modifiable, so it may be possible to prevent accelerated brain aging and perhaps even cognitive decline through healthier sleep,” stated Abigail Dove, PhD, postdoctoral researcher with the Department of Neurobiology, Care Sciences and Society, Karolinska Institutet, who led the study.

Bottom Line: Get some sleep....and make it count.

The study was published online on September 30, 2025 in The Lancet eBioMedicine. A shout-out to Medscape and Dawn Attride for covering the study.