Poor sleep quality may signal the risk of Alzheimer's disease in older adults a study suggests. People with Alzheimer's tend to wake up tired and their nights become even less refreshing as memory loss and other symptoms worsen. However the reason was not fully understood. The study led by the Washington University in St. Louis found that older adults who sleep poorly or have less slow-wave sleep -- deep sleep needed to consolidate memories and wake up feeling refreshed -- have higher levels of tau -- a toxic brain protein. Tau has also been linked to brain damage and cognitive
