What's the science?
Beta-amyloid is a protein that accumulates in the brain in Alzheimer’s disease and with aging. Sleep is thought to be important for clearance of beta-amyloid as a “waste product” and a lack of sleep over time has been associated with higher beta-amyloid in the brain. There is evidence that beta-amyloid is elevated in brain fluid in mice after acute sleep deprivation, however, it is not clear how acute sleep deprivation affects beta-amyloid levels in the human brain. This week in PNAS, Shokri-Kojori and colleagues use Positron Emission Tomography (PET) to assess whether beta-amyloid is elevated after short-term sleep deprivation in humans.
How did they do it?
PET imaging with a radiotracer called 18F-florbetaben which binds to beta-amyloid in the living human brain, was used to measure beta-amyloid levels in 20 healthy participants. Participants were scanned once after a healthy night of sleep and once after a night of sleep deprivation (no sleep) to compare beta-amyloid levels with and without proper sleep. Participants were given questionnaires related to their mood. Data about sleep history and quality were also collected. The authors hypothesized that beta-amyloid levels would be higher in the hippocampus (one of the first brain regions affected by Alzheimer’s disease) after one night of sleep deprivation and that a poor sleep history would be associated with higher beta-amyloid in brain regions known to be affected by Alzheimer’s disease: the medial prefrontal cortex, the hippocampus and the precuneus.
What did they find?
Beta-amyloid accumulation (measured with 18F-florbetaben) was higher in the right hippocampus after one night of sleep deprivation compared to after a good night’s sleep. The extent to which beta-amyloid increased varied between individuals. Mood was found to be worse after sleep deprivation, and this was correlated with the level of beta-amyloid in the regions showing elevated beta-amyloid such as the hippocampus. Reported hours of sleep per night was negatively correlated with beta-amyloid accumulation (i.e. higher sleep, lower beta-amyloid) in the right hippocampus and thalamus where acute sleep deprivation effects were seen. In a separate whole-brain regression analysis, hours of sleep was also negatively correlated with beta-amyloid levels in the putamen, parahippocampal gyrus and right precuneus (brain regions affected by beta-amyloid in Alzheimer’s disease) confirming that these are key regions affected by hours of sleep.
What's the impact?
This is the first study to show that one night of sleep deprivation is associated with higher beta-amyloid in the human brain. This study also highlights the relationship between hours of sleep (self-reported sleep history) and beta-amyloid accumulation. This study emphasizes that sleep is important for regulating beta-amyloid levels and that sleep deprivation could be one risk factor for brain protein accumulation in Alzheimer’s disease and aging.
E. Shokri-Kojori et al., β-Amyloid accumulation in the human brain after one night of sleep deprivation. PNAS (2018). Access the original scientific publication here.