Sleep problems could double risk of dementia in later life

People who experience sleep disorders are at greater risk of developing dementia and other neurodegenerative conditions later in life, new research reveals.

The study provides new insight into the complex relationship between sleep and neurodegenerative disease, and whether disrupted sleep is an early sign of neurodegeneration, or makes someone more likely to go on to develop dementia later.

In the new study, scientists at the UK Dementia Research Institute (UK DRI) at Cardiff University and the U.S. National Institutes of Health (NIH) Intramural Center for Alzheimer’s and Related Dementias, looked at data from over 1 million electronic health records to examine the relationship between sleep and neurodegenerative disease, in one of the largest studies to date.

The meta-analysis, published in the journal npj Dementia, and funded by the UK DRI and the NIH’s National Institute on Aging and National Institute of Neurological Disorders and Stroke found people who had experienced certain sleep disorders were up to twice as likely to go on to develop a neurodegenerative disease in the 15 years that followed.

Interestingly, the study also revealed that sleep disorders increased the risk of Alzheimer’s and Parkinson’s, even in people with a low genetic risk of disease. This suggests that sleep disorders and genetics may influence risk separately, acting by independent mechanisms.

The scientists examined data from three biobanks: the Secure Anonymised Information Linkage (SAIL) databank, UK Biobank, and FinnGen. Across the three biobanks, they were able to obtain accurate, timestamped records of when people were experiencing sleep disorders, as marked in their medical records.

The team looked at people who had been diagnosed with one or more sleep disorders, which were grouped for data analysis into ‘organic’ sleep disorders thought to be cause by physiological factors, with typical examples being narcolepsy, sleep apnoea, circadian rhythm sleep disorders, hypersomnia, (excessive daytime sleepiness), parasomnias (abnormal behaviours or movement during sleep e.g. sleepwalking, night terrors), cataplexy; and ‘non-organic’ sleep disorders not linked to a known physiological condition, including generalised insomnia and nightmares.

Using large-scale statistical analysis methods, the scientists mapped out the relationships between the different neurodegenerative diseases and sleep disorders. They found:

• For dementia (general diagnosis, specific disease not known), incidences of sleep apnoea and other organic and non-organic sleep disorders were associated with an increased risk of dementia in the 10-15 years that followed. The risk was further increased for people recorded as experiencing multiple sleep disorders;
• For Alzheimer’s disease, organic sleep disorders increased risk of Alzheimer’s in the 10-15 years following sleep disorder diagnosis;
• For vascular dementia, sleep apnoea and other organic and non-organic sleep disorders increased risk of vascular dementia in the 5-10 years following sleep disorder diagnosis. The risk was further increased for people recorded as experiencing multiple sleep disorders;
• For Parkinson’s, organic and non-organic sleep disorders increased risk of Parkinson’s in the 10-15 years following sleep disorder diagnosis;

Although large-scale, the study is limited by its observational nature. It also did not account for the use of medication or other interventions to improve sleep, or co-morbidities which may have had an impact.

Next, the authors aim to factor the effect of interventions into further analysis, to examine whether improving sleep leads to a reduction in risk.

“In our study, we wanted to understand the complicated relationship between sleep and dementia. People living with dementia often experience sleep problems, but there is not yet enough evidence to say for sure whether poor sleep increases risk of dementia. We set out to see if we could figure out what order these things are happening. By using biobank data, we had timestamped records of when people had sleep disorders, and exactly when they were subsequently diagnosed with a neurodegenerative disease – rather than relying on self-reporting. Our results are compelling, indicating a clear increased risk of neurodegenerative disease following a sleep disorder, across three large biobank datasets.” Joint first author Dr Emily Simmonds, Bioinformatician at the UK Dementia Research Institute at Cardiff University

“One of the exciting things about identifying people at higher risk of developing a neurodegenerative disease 10-15 years before diagnosis, is that it gives us time to implement treatments that may delay or prevent development of disease. In the case of sleep disorders, future studies could look at the effectiveness of treatment with a continuous positive airway pressure machine (CPAP) and/or sleep medications to see if those interventions can lower the associated risk of later developing an neurodegenerative disease.” Joint first author Kristin Levine, Data Scientist at the NIH’s Center for Alzheimer’s and Related Dementias

Reference: Simmonds, E., Levine, K.S., Han, J. et al. Sleep disturbances as risk factors for neurodegeneration later in life. npj Dement. 1, 6 (2025). https://doi.org/10.1038/s44400-025-00008-0