A fitful night’s sleep and a habit of daytime catnapping may be an early-warning sign of Alzheimer’s dementia, according to new research conducted in humans and mice.

Restless nights and sleepy days are a common pattern in patients with full-blown Alzheimer’s. Those disrupted circadian rhythms are a symptom that can upend the lives of caregivers and cause confusion and anxiety in patients. Less dramatic levels of sleep disruption, including trouble falling asleep and more frequent night-time wakening, are also typical as people age.