Sleep disorders increase dementia risk - study

People who experience sleep disorders are at greater risk of developing neurodegenerative conditions, including dementia, new research has found.

The study, conducted by researchers at Cardiff University, found that diagnoses of sleep disorder made people up to twice as likely to develop a neurodegenerative disease in the 15 years that followed.

The peer-reviewed study used data from more than a million electronic health records.

"This increased risk was occurring independently of genetic risk factors for Alzheimer's and Parkinson's, with sleep disorders almost 'compensating' for low genetic risk," said Prof Valentina Escott-Price, from the UK Dementia Research Institute at Cardiff University.

The researchers examined data from three biobanks – facilities that store biological samples and are used for health research – from which they were "able to obtain accurate, timestamped records of when people experienced sleep disorders".

The team analysed those who had been diagnosed with one of more sleep disorder, grouping them into those associated with "circadian rhythm" – or body clock – such as sleepwalking and narcolepsy, and "non-organic" sleep disorders not linked to a known psychological condition, including generalised insomnia and nightmares.

The key findings were:

• Circadian sleep disorders and non-organic sleep disorders were associated with an increased risk of dementia in the 10 to 15 years that followed. The risk was further increased for those with multiple sleep disorders.

• Circadian sleep disorders increased the risk of Alzheimer's in the 10 to 15 years following sleep disorder diagnosis.

• Circadian sleep disorders and non-organic sleep disorders increased the risk of vascular dementia in the 5 to 10 years following sleep disorder diagnosis. The risk was further increased for those with multiple sleep disorders.

• Circadian sleep disorders and non-organic sleep disorders increased risk of Parkinson's in the 10 to 15 years following sleep disorder diagnosis.

Dr Emily Simmonds, bioinformatician at the UK Dementia Research Institute at Cardiff University, said the study aimed to "understand the complicated relationship between sleep and dementia".

She said: "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.

"Our results are compelling, indicating a clear increased risk of neurodegenerative disease following a sleep disorder."

Prof Escott-Price, also from Cardiff University, said that while further investigation is needed the research "points towards sleep disorders as a risk factor for these conditions".

Future research will examine whether improving sleep through the use of medication leads to a reduction in risk.