Heads up if you have poor sleep.

Sleep loss may be an early symptom of Alzheimer's disease, a new study has warned. Sleep is disrupted in people who likely have early Alzheimer's disease but do not yet have the memory loss or other cognitive problems characteristic of full-blown disease, researchers at Washington University School of Medicine have found.

The finding confirms earlier observations by some of the same researchers. Those studies showed a link in mice between sleep loss and brain plaques, a hallmark of Alzheimer's disease. Early evidence tentatively suggests the connection may work in both directions: Alzheimer's plaques disrupt sleep, and lack of sleep promotes Alzheimer's plaques.