Researchers have also found that people who have a greater risk of developing the progressive condition are less likely to have insomnia.
The findings, published in the journal Neurology, are based on an analysis of data gathered from different genome-wide association studies, which involve identifying genes associated with various human diseases.
The team, which included scientists from Imperial College London, said they found no evidence of disturbed sleep patterns causing Alzheimer’s disease but added those at higher risk are also likely to have shorter sleep duration.
However, the scientists warned the effect of these associations are quite small and show only a possible link – not cause and effect.
The researchers looked at data from the International Genomics of Alzheimer’s Project, involving 63,926 people, as well as information from the Psychiatric Genomics Consortium, which included 18,759 participants.
Also included in the study was data from nearly 450,000 people from the UK Biobank, which has health and genetic information on around half a million people.
We wanted to find out if there are causal relationships between different sleep patterns and depression and Alzheimer's
The scientists used a technique, called Mendelian randomisation, to evaluate the relationship between different sleep patterns, major depressive disorder, and the genetic risk of Alzheimer’s disease.
Study author Dr Abbas Dehghan, of Imperial, said: “We know that people with Alzheimer’s disease often report depression and various sleep problems, like insomnia.
“We wanted to find out if there are causal relationships between different sleep patterns and depression and Alzheimer’s.”
The researchers said they found no evidence of cause and effect between major depressive disorder and Alzheimer’s.
However, they did find people with twice the genetic risk for Alzheimer’s disease were 1% more likely to call themselves “morning people”, when compared to people at lower genetic risk.
This research shows a small link between different sleep patterns and the risk of developing Alzheimer's disease, but did not find any evidence for sleep disturbance causing the disease
They also found those with twice the genetic risk of Alzheimer’s had a 1% lower risk of insomnia.
The researchers said that most of the people in the study were of European ancestry, so the results may not apply to those from other ethnic backgrounds.
Commenting on the study, Dr Sara Imarisio, head of research at Alzheimer’s Research UK, said: “Many of us have experienced a bad night’s sleep and probably know that it can have an impact on our memory and thinking in the short term, but an intriguing question is whether sleep problems have a long-term effect on the brain.
“This research shows a small link between different sleep patterns and the risk of developing Alzheimer’s disease, but did not find any evidence for sleep disturbance causing the disease.”
She added: “Dementia is not an inevitable part of ageing and more evidence on the complex topic of sleep is needed before we can make a judgement on its impact on dementia risk.”
