Taking too long to enter the phase of sleep in which we dream may be an early sign of Alzheimer's disease. This is the conclusion of an international team of researchers who studied the sleep patterns of around 100 patients with either Alzheimer's or its precursor in comparison with their cognitively healthy counterparts.

Taking longer to drift into the dreaming phase – known as rapid eye movement (REM) sleep – could be an early sign of Alzheimer's disease, potentially opening up new ways to diagnose and treat the devastating condition before it fully develops.