Just one night of bad sleep may lead to more of a protein linked to Alzheimer’s disease building up in the brain.
People with Alzheimer’s disease tend to have sticky clumps of beta-amyloid protein in their brains, although the roll these plaques play in the condition is unclear. It’s possible this protein helps cause the condition, or instead that the protein forms plaques in the brain in response to the disease.
Now researchers have found that one night of poor sleep has a detectable effect on the levels of beta-amyloid in the brain. Ehsan Shokri-Kojori, at the National Institutes of Health in Maryland, and his team discovered this by using a radioactive tracer to measure beta-amyloid in the brains of 20 volunteers over the course of two nights.
For one of the nights, the participants were allowed a restful period of sleep, but they were deprived sleep on the other night. When scans were used to track the tracer, the team found that when sleep was restricted to only around five hours, beta-amyloid increased in two regions of the brain that are known to be vulnerable to damage in Alzheimer’s disease.
These regions were the hippocampus, which is important for memory, and the thalamus, which helps relay signals in the brain and regulates sleep and consciousness.
Sleep is thought to be important for clearing out waste from the brain, which may explain why people had more beta-amyloid in their brains after a bad night’s sleep.
Poor quality sleep has been linked to Alzheimer’s before. People with the condition often experience disrupted sleep, and this can begin several years before other Alzheimer’s symptoms begin to show. It is not clear yet whether disrupted sleep is just a symptom of the condition, or if it contributes to it.
“There is growing evidence of a link between disrupted sleep and Alzheimer’s disease, but it is difficult to tease apart cause and effect to determine whether sleep problems might cause Alzheimer’s brain changes, or vice-versa,” says David Reynolds, of the charity Alzheimer’s Research UK.
Journal reference: PNAS, DOI: 10.1073/pnas.1721694115