Researchers have been working for decades to unravel the secrets of Alzheimer’s disease, a type of dementia that seems to be linked to the buildup of certain proteins, called Aβ and tau, in the brain. Unfortunately, how and why those proteins build up is still a mystery. One group of researchers took a step forward in understanding why Alzheimer’s is so damaging to a person’s memory this week. Their research has revealed that the sleep problems experienced by many of those with Alzheimer’s are playing a key role both in memory issues and in the progress of the disease.
How is sleep related to memory?
Sleep has long been known to be important for storing memories and remembering them later. Sleep seems to be the brain’s way of reviewing what it experienced and organizing it so that it can find it later. Without sleep, the brain doesn’t have a chance to scan through the information, pick out the important stuff and store it, which means it has a harder time remembering things when asked to do so later on.
There are two parts of the brain that are important in this process. The first is the hippocampus, which is a small, seahorse-shaped part of the brain that sits close to your ear. The hippocampus is the waystation for memories. It’s the main place where experiences are assessed and picked for holding for the short-term. But the hippocampus is only part of the story. An area called the medial prefrontal cortex located in the middle part of the front of the brain is involved in taking important short-term memories and storing them for the long term.
Where does Alzheimer’s disease fit in?
Memory is one of the first things affected by Alzheimer’s disease. People with the disease often start off struggling to remember small things, like what they had for breakfast or where they put their wallet, to larger problems, like where they live or who their children are. Past research has shown that this happens because the hippocampus is one of the first areas of the brain hit with protein buildup in Alzheimer’s.
The research team wondered if sleep, which is so important for memory, might also be involved. One of the early signs of Alzheimer’s disease is a change in the way a person sleeps. A person might start sleeping at odd hours of the day or have trouble staying asleep all night. This can show up as changes in brain waves during a person’s sleep even before they start to notice actual sleep troubles. The researchers wondered if these constant sleep disruptions might add to the damaging process of Alzheimer’s to block memory even more.
How did they study this and what did they find?
The researchers recruited 26 adults between the age of 65 and 81 who didn’t have any signs of Alzheimer’s or sleep problems. They looked at their brains in three ways: with a PET scan to measure the amount of Alzheimer’s-related Aβ protein in their brain; with an MRI to watch how their brain worked when they tried to remember things; and with an EEG to measure changes in their brain waves as they slept. They used all of this information to see which people had more Alzheimer’s protein in their brain and whether that was related to how they slept and how their brain stored and retrieved memories.
The found that people who had more Aβ in their brain had more problems getting their brain into the right kind of sleep to store memories. They saw that Aβ gathered both in the hippocampus where it was seen in the past and in the frontal lobe of the brain where long-term memory storage happened. This meant that a person’s memory took two hits as it started to suffer from Alzheimer’s: a person would lose the kind of sleep they needed to store memories and the proper functioning of the brain areas involved in forming memories. These findings tied into other research showing that poor sleep might even increase the amount of Aβ in a person’s brain, leading to a deadly spiral of worse sleep causing more protein buildup causing worse sleep.
How does this apply to me?
This study emphasizes how important sleep is when we talk about memory and points to the central role it might play in Alzheimer’s. The hope is that these findings might spur new ways of thinking about the cause of Alzheimer’s and ways to try and treat it. If you notice that an older loved on has had a dramatic change in the way they’re sleeping, it might be wise to have them assessed. While there isn’t much we can currently do to treat Alzheimer’s disease, there’s a lot we can do to plan for how it might affect someone’s life.