Waking up with a feeling of tiredness despite having slept the recommended time may be a sign of deterioration of the brain.
After monitoring the sleep of 119 people over the age of 60 and practicing brain scanners, a group of scientists found that those with less slow-wave sleep – the deep sleep needed to consolidate memories and wake up refreshed – have higher levels of tau brain protein.
Elevation of this substance is a sign of Alzheimer's disease and is related to brain damage and cognitive decline in other diseases.
The new study is one of the first to relate sleep quality – not quantity – to alzhimer. The importance is that this disease can appear up to two decades before the symptoms occur, so the challenge is to get an early diagnosis. In this sense, the new work indicates that sleep quality can be a useful marker.
The results were published yesterday in the journal Science Translational Medicine.
In an interview with "El Mercurio," lead author Brendan Lucey, a professor of neurology at the University of Washington, said: "We believe that the changes in the brain that the disease produces, especially the tau buildup, they interrupt activity of sleep soon after the onset of problems with thought and memory. "
The same is the opinion of Claudio Hetz, director of the Millennium Institute of Biomedical Neuroscience (BNI).
"It is likely that the problem of sleep is a side effect of the alzhimer," agrees Hetz.
"It's an important result, the funny thing is that changes in sleep can be measured and give a red light that maybe it's time to go to the neurologist." He adds: "Probably this type of measures, along with other molecular measures, will help predict the risk."
Lucey adds that the studied dream (slow wave) is the deeper stage of the NREM phase (see box) and its changes may manifest with awakenings at night, but they may also be barely perceptible and do not decrease sleep time.
Hence the importance of consulting the doctor if you think you had little rest, even when you slept the recommended time, which for adults is seven to eight hours a day.
This is confirmed by Carolina Aguirre, chief neurologist at UC Christus Health Network's Sleep Center.
"The study you are saying is that if I sleep eight hours or more, but I wake up tired, you have to consult."