People living with Alzheimer’s disease often struggle to get a good night’s sleep. A new study suggests the problem may not be caused by the disease itself, but by the brain’s own defence system overreacting.
The study, published in Alzheimer’s & Dementia, found that reducing the activity of the brain’s defence cells helped animals with Alzheimer’s sleep for more than two extra hours each day. The findings could open the door to new treatments that focus on improving sleep, an important part of keeping the brain healthy.
Scientists say the brain’s defence cells are meant to protect it from harm. But when harmful protein clumps linked to Alzheimer’s begin to build up, these cells become overactive and trigger inflammation. Instead of helping, they may end up keeping the brain awake.
“It’s not the protein build-up itself that is causing the sleep loss. It’s the brain’s defence cells reacting to it,” the researchers said.
For many years, experts believed that sleep problems in Alzheimer’s were mainly caused by damaged brain cells or the build-up of harmful proteins. This study suggests the body’s own response to those proteins may be the bigger reason people lose sleep.
To test the idea, researchers studied mice that develop Alzheimer’s-like changes in the brain. Another group of healthy mice was used for comparison.
The scientists monitored the animals’ sleep and brain activity before giving some of them a drug that temporarily removed most of the brain’s defence cells.
Just two weeks later, the results were clear.
The mice with Alzheimer’s slept for more than two extra hours every day. They also spent more time in deep sleep, the stage when the brain repairs itself, stores memories and clears away waste.
What surprised researchers most was that the harmful protein build-up in the brain stayed the same. Even without removing the protein, sleep improved simply because the defence cells were no longer causing as much inflammation.
The study also found that sleep problems begin early in Alzheimer’s, around the same time the harmful proteins first appear. As the disease progresses and more protein builds up, sleep does not become much worse.
This suggests the brain’s defence system may trigger sleep problems early, and the effects continue throughout the disease.
Researchers also discovered that Alzheimer’s affects sleep differently from normal ageing.
As people grow older, they naturally spend less time dreaming. But Alzheimer’s mainly reduces deep sleep, which is the body’s most important time for rest and recovery.
“Deep sleep is essential because it’s when the brain repairs itself, strengthens memories and clears away waste. Losing this stage means the brain misses one of its most important cleaning processes, which may lead to even more damage,” the researchers said.
Poor sleep has already been linked to memory problems and faster mental decline. Scientists believe that restoring deep sleep could help protect the brain and improve quality of life for people living with Alzheimer’s.
The researchers also say simple brain-wave tests could one day help detect Alzheimer’s earlier. Portable devices that measure brain activity may allow doctors to spot changes before symptoms become severe, making it easier to monitor people from their homes.
Although more research is needed to confirm the findings in humans, the study offers new hope that treating the brain’s overactive defence system, rather than focusing only on harmful proteins, could become a new way to tackle Alzheimer’s disease.
