Losing just one night's sleep linked to Alzheimer's disease

Losing just one night of sleep fuels brain proteins linked to the development of Alzheimer's disease, a new research warns.

The study, published in the journal Neurology, found that when young, healthy men were deprived of just one night of sleep, they had higher levels of tau, a biomarker for Alzheimer's disease, in their blood than when they had a full, uninterrupted night of rest.

Tau is a protein found in neurons that can form into tangles. These accumulate in the brains of people with Alzheimer's disease. It can start to develop in the brain decades before symptoms of the disease appear.

Previous studies of older adults have suggested that sleep deprivation can increase the level of tau in the cerebral spinal fluid.

"Our exploratory study shows that even in young, healthy individuals, missing one night of sleep increases the level of tau in blood suggesting that over time, such sleep deprivation could possibly have detrimental effects," said study author Jonathan Cedernaes, from Uppsala University in Sweden.

The study involved 15 healthy, normal-weight men with an average age of 22. They all reported regularly getting seven to nine hours of quality sleep per night.

There were two phases to the study. For each phase, the men were observed under a strict meal and activity schedule in a sleep clinic for two days and nights. Blood samples were taken in the evening and again in the morning.

For one phase, participants were allowed to get a good night of sleep both nights.

For the other phase, participants were allowed to get a good night of sleep the first night followed by a second night of sleep deprivation.

During sleep deprivation, lights were kept on while participants sat up in bed playing games, watching movies or talking.

Researchers found that the men had an average 17 per cent increase in tau levels in their blood after a night of sleep deprivation compared to an average  two per cent increase in tau levels after a good night of sleep.

Researchers also looked at four other biomarkers associated with Alzheimer's but there were no changes in levels between a good night of sleep and one night of no sleep.

"It's important to note that while higher levels of tau in the brain are not good, in the context of sleep loss we do not know what higher levels of tau in blood represent," said Cedernaes.

According to the researchers, when neurons are active, production of tau in the brain is increased. Higher levels in the blood may reflect that these tau proteins are being cleared from the brain or they may reflect elevated tau levels in the brain.