People who have trouble sleeping may be at higher risk of developing memory problems, new research shows.

People who woke frequently in the night had a higher risk of developing Alzheimer’s disease, according to work to be presented at the American Academy of Neurology meeting in New Orleans in April.

Other research has shown a link between impaired sleep and multiple-personality disorder, as well as other forms of dissociation.

And research in mice has shown that disrupted sleep can actually cause an increase in the buildup of amyloid plaque in the brain — buildup that happens years before any outward symptoms of Alzheimer’s occur.

To see whether disrupted sleep affected humans, the researchers took 100 patients, half of whom had a family history of Alzheimer’s, and monitored their sleep patterns for 14 days. They found that even though participants spent about eight hours in bed, on average, they spent only about 6.5 hours sleeping, because they woke up repeatedly during the night.