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Changes in Nighttime Sleep Duration and Their Association With Cognitive Decline and Dementia Risk
Marieclaire Overton1, Sölve Elmståhl1, Rani Basna1
1Division of Geriatric Medicine, Department of Clinical Sciences in Malmö, Lund University, Skåne University Hospital, Malmö, Sweden.
Journal of Sleep Research
|July 29, 2026
Summary
Prolonged sleep duration and increased sleep variability are linked to faster cognitive decline and a higher risk of dementia. Shortened sleep showed no significant association with these outcomes.
Area of Science:
- Neurology
- Sleep Medicine
- Gerontology
Background:
- Changes in sleep patterns are common in aging populations.
- Understanding the relationship between sleep duration variability and cognitive health is crucial for preventative strategies.
Purpose of the Study:
- To investigate the association between changes in nighttime sleep duration and cognitive decline.
- To examine the risk of incident dementia in relation to altered sleep duration and variability.
Main Methods:
- Analysis of 3057 participants from the 'Good Aging in Skåne' study with normal baseline sleep (6-8 hours).
- Longitudinal follow-up up to 20 years, assessing self-reported changes in sleep duration (>1 hour increase/decrease) and sleep variability (SD).
- Cognitive decline measured by global cognition; dementia risk assessed using Cox proportional hazard models.
Main Results:
- Longitudinal prolonged sleep (>1 hour increase) was significantly associated with cognitive decline.
- Greater sleep variability also correlated with steeper cognitive decline.
- Prolonged sleep increased dementia risk by 131% (HR=2.31); higher sleep variability increased risk by 49% (HR=1.49). Shortened sleep was not significantly associated with cognitive decline or dementia risk.
Conclusions:
- Changes in sleep duration, particularly prolonged sleep and high variability, are significant markers for accelerated cognitive decline.
- Increased sleep variability and prolonged sleep duration are associated with a higher risk of developing dementia.
- These sleep characteristics may serve as early indicators of future cognitive impairment, warranting further investigation.
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