US scientists found those with disturbed night-time sleep patterns, leading to daytime snoozing, were more likely to have the first traces of the disease – and they occur much earlier than thought.
Researchers said it was unclear if disturbed sleep put people at risk of Alzheimer’s or if disease-related brain changes caused disrupted sleep rhythms.
But the study found those who catnapped, even if they got enough sleep, had a greater probability of early Alzheimer’s.
The findings add to growing evidence linking disruptions in the body clock, or circadian rhythms, to the brain disease, which has no cure.
It is hoped doctors will identify at-risk patients in advance when new drugs are more likely to work.
Alzheimer’s damage can take root up to 20 years before clinical symptoms appear. Scientists suspect it is one of the reasons medications have failed so far because they are given to trial participants too late.
Researcher Erik Musiek of Washington University said: “Sleeping for eight hours at night is very different from getting eight hours of sleep in hour increments during daytime naps.”
He added: “It’s the first data demonstrating that the disruption of circadian rhythms could be accelerating the deposition of plaques.”
People with Alzheimer’s have beta-amyloid, which are clumps of toxic brain protein, or plaques, which cause brain tissue loss and nerve cell death, leading to memory loss.
Of the 189 cognitively normal people, with an average age of 66, who took part, 50 had abnormal results.
It suggested they had the neuron-killing protein clumps. All woke up regularly during the night or nodded off in the day or both.
Dr David Reynolds, chief scientific officer at Alzheimer’s Research UK, said: “Studies like this could lay the groundwork for new ways to detect the condition earlier.”