Poor sleep could be a cause of Alzheimer's disease, research has suggested.
A lack of regular deep sleep allows a toxic protein known as beta-amyloid to increase in the brain, attacking the mind's memory faculties.
The study, by Berkeley, University of California, said a "vicious cycle" emerges where the protein build-up corrodes memory and disrupts sleep further.
Over time, this can develop into the degenerative brain disease Alzheimer's, a form of dementia characterised by the death of brain cells.
The relationship between sleep and memory loss prompted by beta-amyloid was suspected after heavy build-ups were discovered both in people suffering from Alzheimer's and those with sleeping disorders.
Researchers say they hoped they could prevent future memory loss through the treatment of sleep deprivation with methods including exercise and behavioural therapy.
A lack of non-REM sleep was identified as playing an important role in the process, as it is a form of deep sleep which helps the mind transfer short-term memories into an area of the brain used for longer-term retention.
Professor Matthew Walker told Nature Neuroscience, which published the study: "This discovery offers hope. Sleep could be a novel therapeutic target for fighting back against memory impairment in older adults and even those with dementia."