Study using SAIL data finds sleep problems could double risk of dementia in later life

A study using data from our funded centre, SAIL Databank, has found that a diagnosis of a sleep disorder could make individuals up to twice as likely to develop a neurodegenerative disease within the following 15 years.

Scientists from Cardiff University, worked with colleagues at the NIH Intramural Center for Alzheimer’s and Related Dementias in the United States in one of the largest studies of its kind.

The research team examined the relationship between sleep disorders and neurodegenerative disease, using data from more than one million electronic health records. The study explored whether disrupted sleep serves as an early warning sign of neurodegeneration or whether it increases a person’s likelihood of developing dementia later. 

The researchers analysed data from three major biobanks: the SAIL Databank in Swansea, the UK Biobank, and FinnGen in Finland. Across these datasets, they were able to access accurate, timestamped medical records showing when individuals were diagnosed with sleep disorders. 

The study focused on people who had been diagnosed with one or more sleep disorders. For the purposes of data analysis, these disorders were grouped into categories, including those associated with circadian rhythm disruption—such as narcolepsy, sleep apnoea, hypersomnia (excessive daytime sleepiness), and parasomnias (abnormal behaviours or movements during sleep, including sleepwalking and night terrors)— as well as cataplexy. 

The researchers also examined ‘non-organic’ sleep disorders, which are not linked to a known physiological cause and include conditions such as generalised insomnia and nightmares. Using large-scale statistical methods, the team mapped the relationships between different neurodegenerative diseases and sleep disorders. Several important patterns emerged. 

For dementia where the specific disease type was not recorded, both circadian sleep disorders and non-organic sleep disorders were linked to an increased risk of developing dementia within 10 to 15 years of the sleep disorder diagnosis. This risk was even higher among individuals with multiple types of sleep disorders. In cases of Alzheimer’s disease, circadian sleep disorders were associated with an increased risk of developing the condition within 10 to 15 years following diagnosis of the sleep disorder.

 For vascular dementia, both circadian sleep disorders and non-organic sleep disorders were linked to a heightened risk within 5 to 10 years. This risk was again further increased in people with multiple sleep disorder diagnoses. Similarly, for Parkinson’s disease, both circadian and non-organic sleep disorders were associated with an increased risk of developing the condition within 10 to 15 years. 

Importantly, the study also found that sleep disorders increased the risk of Alzheimer’s and Parkinson’s disease independently of genetic risk. Even among people with a low genetic predisposition, having a sleep disorder increased their overall risk. This suggests that sleep disorders and genetic factors are likely to influence disease risk separately, through independent mechanisms.

Dr Emily Simmonds from Cardiff University said: “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 dementia risk. 

“We set out to see if we could determine the sequence of events. By using biobank data, we had timestamped records of when people experienced sleep disorders and exactly when they were subsequently diagnosed with a neurodegenerative disease - rather than relying on self-reported information.” 

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