A preliminary study by researchers at Uppsala University, Sweden has found that losing just one night of sleep may increase levels of tau – a biomarker for Alzheimer’s disease. Published in Neurology, this study found levels of tau were increased in the blood of young, healthy men who were deprived of just one night of sleep, and could contribute to developing the disease later in life.

Tau is a protein found in neurons that has been identified to have a link with Alzheimer’s disease by forming neurofibrillary tangles in the brains of people with the disease. Some studies have suggested that tau levels can increase in cerebral spinal fluid due to sleep deprivation, and accumulation of it can start decades before symptoms of the disease appear.

15 healthy, normal-weight men with an average age of 22 participated in the study, all who reported regularly getting seven to nine hours of quality sleep per night. Blood samples were collected before and after getting a good night of sleep and a night of sleep deprivation. Participants were kept awake with movies, games, and talking with the lights kept on.

Tau levels were found to increase by 17% in the blood after a night of sleep deprivation, compared with 2% after a good night’s sleep. No changes were found in four other biomarkers associated with Alzheimer’s disease. This study has some limitations though, and future studies could include women or older people, and use more participants to fully see if there is a correlation.

“It’s important to note that while accumulation of tau in the brain is not good, in the context of sleep loss, we do not know what higher levels of tau in blood represent” said Jonathan Cedernaes, MD, PhD, from Uppsala University in Sweden. “When neurons are active, release 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 an overall elevation of the concentration of tau levels in the brain. Future studies are needed to investigate this further, as well as to determine how long these changes in tau last, and to determine whether changes in tau in blood reflects a mechanism by which recurrent exposure to restricted, disrupted or irregular sleep may increase the risk of dementia. Such studies could provide key insight into whether interventions targeting sleep should begin at an early age to reduce a person’s risk of developing dementia or Alzheimer’s disease.”