BEING a “morning person” could mean you are more likely to suffer from Alzheimer’s, a new study has found.
Those who spring out of bed bright and early are at increased genetic risk of the disease, according to scientists.
Researchers from Imperial College London studied more than half a million people and found disturbed sleep does not cause dementia.
But individuals carrying mutations associated with the disorder were more likely to get up at the crack of dawn.
They also tended to be restless sleepers and spend less time in the land of nod – but there was no connection with insomnia or depression.
The findings shed fresh light on the development of the devastating illness which has been linked to lack of sleep.
Lead author and epidemiologist Dr Abbas Dehghan said: “We know 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 study published in Neurology is the first to evaluate the relationships between all three – and found they are more complicated than previously believed.
It pooled data from genetic studies that included 21,982 patients with Alzheimer’s disease and 41,944 healthy peers.
This was compared to 18,759 individuals with and without major depressive disorder and 446,118 people whose sleep habits had been recorded.
The risk of Alzheimer’s was determined based on genetic studies where the disease was diagnosed by autopsy or clinical examination.
Morning people – or “larks” – are early to rise, peak earlier in the day and are tired earlier in the evening.
Evening people or “owls” find it harder to get up in the morning, are productive later into the evening and prefer to go to sleep late.
The researchers used a technique called Mendelian randomisation, which uses genetic variants known to be connected with a potential risk factor, such as insomnia, to discover the relations to a disease.
They found no evidence of a link between Alzheimer’s and sleep problems – or depression.
But people with twice the genetic risk for Alzheimer’s were one per cent more likely to call themselves “morning people”.
And their risk of insomnia was reduced by one percent.
The effect of the association is small and shows only a possible link – not cause and effect, according to the researchers.
Dr Dehghan said ageing populations have led to an increasing prevalence of both Alzheimer’s disease and depression.
But it’s not known if one causes the other – or if they share any common risk factors.
Dr Dehghan said: “In this study, we found evidence supporting a potential causal influence of Alzheimer’s disease on sleep disturbances.
“However, we did not find evidence supporting a causal role of disturbed sleep patterns for Alzheimer’s disease.”
We found Alzheimer’s disease may causally influence sleep patterns
In other words, Alzheimer’s may lead to sleep disorders – rather than the other way round.
Dr Dehghan said: “We found Alzheimer’s disease may causally influence sleep patterns.”
Previous research has found night owls who stay up late and struggle to get out of bed in the morning are ten percent more likely to die sooner than larks.
A team at Surrey University said the ongoing stress of operating in a traditional nine-to-five society was having a huge impact on millions of people – and could be shortening their lives.
They suggested allowing evening types to start and finish work later, where practical.
The study analysed nearly 500,000 Brits, with nine per cent describing themselves as evening people and 27 per cent identifying as morning types.
If extrapolated to the entire population it would mean around 5.8 million people were at greater risk of early death because they were out of sync with the environment.