Hallmarks of the disease include the build-up of harmful proteins in the brain - amyloid plaques and tau tangles.
Amyloid is a protein that folds and forms plaques. The more tau tangles there are, the worse the symptoms tend to be.
In healthy brains, tau acts as a stabiliser, but when the proteins become defective, they can form into bundles of tangled filaments, which are thought to impede communication between brain cells, leading to the neurodegeneration and reduced cognitive ability seen in conditions like Alzheimer's disease.
Lead scientist Dr Barbara Bendlin, from the University of Wisconsin-Madison in the United States, said: "Previous evidence has shown that sleep may influence the development or progression of Alzheimer's disease in various ways".
The work was funded by the MRC, the European Union, US National Institutes of Health and the Department of Pathology and Laboratory Medicine, Indiana University School of Medicine.
"Animal studies suggest sleep affects development of brain changes, but brain changes in turn also affect sleep", Bendlin said.
Not necessarily. Bendlin said these findings can not prove that poor sleep causes Alzheimer's disease. This provides a window of opportunity for intervention, she said. "But that does not mean cause and effect".
"Overall, this study confirms the relationship between early Alzheimer's disease and sleep disturbance", Ju said, "and (it) expands - in terms of both time and symptoms - the window in which sleep-wake problems can be assessed for and treated, with the hope of reducing the risk of dementia due to Alzheimer's disease". In a recent study, investigators examined 101 cognitively normal individuals--with an average age of 63 years--who completed sleep questionnaires.
The study volunteers gave a sample of spinal fluid to be tested for markers of Alzheimer's disease.
Dr Doug Brown, director of research at the charity Alzheimer's Society, said: "This study adds to previous evidence that poor quality sleep may be associated with signs of Alzheimer's". Examples included: "During the past four weeks, how often did you get the amount of sleep you needed?"
Given our busy and chaotic lives, as many as one in three people have trouble sleeping - either they are not getting enough sleep, or suffer disturbed sleep or in some cases, it's a combination of both.
Not everyone with sleep problems in the study had abnormalities in their spinal fluid.
One thing that could have thrown the findings off is that the participants reported their own sleep problems. The research in mice was particularly interesting because it showed that mice who slept well reduced their levels of beta amyloid, effectively clearing the toxin from their brains.
It is a verified fact that Alzheimer patients have issues with sleep.
The report was published online July 5 in the journal Neurology.