Chronic sleep deprivation increases plaques in the brain thought to be a main cause of dementia, research shops.
A protein called orexin that helps to regulate the sleep cycle is directly involved, say the scientists at Washington University School of Medicine and Barnes-Jewish Hospital.
Amyloid beta, which forms plaques, rises and falls with sleep and wakefulness, with deprivation leading to a 25 per cent rise.
Injecting orexin into the brains of mice made them stay awake longer and increased amyloid beta levels, putting them at greater risk of developing plaques.
Neurologist Professor David Holtzman explained that lack of sleep can have "potential long-term impacts on brain health".
It is thought that plaques and tangles "silt up" the brain and cause Alzheimer's.
Earlier this week, it was suggested that difficulties in money management could indicate Alzheimer's, with the University of Alabama in Birmingham saying financial problems may be seen a year ahead of a dementia diagnosis.
Please click here for advice to help you find the right type of care.