By Min Zan
I never really thought about dementia until my mom got it. It was strange because I didn’t even realize she had Alzheimer’s until one day she asked me when we first met. I didn’t understand the full extent of her memory loss, partly because I didn’t want to believe it, and partly because she was clever at hiding her brain problems. She found ways to work around her memory issues, even though her brain was getting worse due to Alzheimer’s. She had done something similar before when she had a stroke four years ago. Back then, she lost the ability to read, but she worked hard and learned to read again.
I wondered why she could adapt so well after the stroke but struggled with dementia. This got me thinking about my own brain health and what I could do to protect it. For nearly 30 years, scientists have known about a mysterious ability called “cognitive reserve.” Some people can keep their brains working normally even when there are problems like plaques from Alzheimer’s. But it’s been hard to figure out how this works in the brain.
Now, we’re finally starting to understand how cognitive reserve works. This new knowledge might lead to better treatments for dementia and help us keep our minds sharp as we get older. Surprisingly, it turns out that just learning a new language or doing crossword puzzles might not be enough.
The idea of cognitive reserve first came about 30 years ago when a neuropsychologist named Yaakov Stern and his team at Columbia University in New York discovered that people with more education or challenging jobs were less likely to get Alzheimer’s. They thought that all the mental effort over the years created a “reserve” that delayed the signs of Alzheimer’s.
At first, people didn’t take this idea seriously. Stern said that his colleagues even made fun of it because it seemed unbelievable that something like education could fight against the problems caused by Alzheimer’s.
Stern called this ability “cognitive reserve” to make it different from another idea called “brain reserve” created a few years earlier by Robert Katzman at the University of California, San Diego. Katzman looked at the brains of elderly people who had passed away and found that some of them had a lot of plaques linked to Alzheimer’s, but they still had good thinking abilities. He thought this happened because they had bigger, heavier brains with more neurons. This extra “brain reserve” helped protect their brains from the damage caused by plaques.
Brain reserve relates to the size of the brain, which means how many neurons and connections there are for information to move around. It’s like the computer’s hardware – the stuff you can touch and see. But we used to think that the brain’s hardware had a set limit, and it couldn’t change. However, now we know that the brain can create new neurons, even when we’re adults. Also, many things can influence how well the brain’s hardware works. This brings us to the third part of the puzzle, brain maintenance, which means the things we do in our lives and the environment that help keep our brains in good shape.
So, there are three things that work together to help some people keep their thinking skills as they get older: cognitive reserve, brain reserve, and brain maintenance. They’re all connected and work together. Dorina Cadar from the UK says these three things are very related.
We’ve seen through many studies that these things really do protect our thinking skills. For example, a study in 2020 followed over 12,000 people who were 50 or older. It found that things like education, the kind of job you have, and the choices you make in life, like how you spend your free time and who you’re with, all add up to create a higher level of cognitive reserve. This helps lower the risk of dementia.
Cognitive reserve is hard to see in the brain or measure directly, but researchers like Stern have found ways to identify the brain networks linked to it. We often measure it using things like cognitive tests. We’ve learned a lot about what can make it stronger. Some things, like our genes, are mostly out of our control. But other things, like being social and staying engaged with people when you’re older, can really help. Socializing challenges your mind because you need to remember names, faces, and how to chat with others, and it reduces stress. A lack of social interaction might have contributed to my mom’s dementia. She suffered from depression and isolated herself from others for months.
Stress, being overweight, and eating unhealthy food can harm our reserves because they cause ongoing inflammation, which messes up many brain functions. It makes it hard for the brain to use glucose and messes with how our nerves work. Also, it makes the effects of “inflammation” worse, which is the low-level inflammation that happens as we get older.
On the flip side, a good night’s sleep can really help our brain stay sharp. A study from this year found that a specific part of our sleep, called non-rapid eye movement (NREM), is super important. This is because it helps us remember things and gets rid of harmful stuff in our brain that messes with how it works.
Something surprising is that staying active is also great for our brain. A study in 2020 looked at almost 130,000 people in the US. It found that people who don’t move around much have nearly double the risk of losing their thinking abilities compared to active people. Exercise is like a superhero for our brain. It keeps our heart and blood flow in good shape, reduces brain inflammation, and boosts a special thing called neurotrophic factor, which helps our memory centre (the hippocampus) get bigger. Exercise also helps us sleep better, which is important for our memory.
Doing activities that make your brain work hard is also a big help. Speaking more than one language is like a super brain workout. Bilingual people can keep their thinking skills longer, even though they may eventually have the same risk of Alzheimer’s. But you don’t need to rush to learn a new language. What matters is doing activities that challenge your brain, not a specific thing. For example, a study in 2015 looked at people aged 60 to 90 who spent time quilting or doing digital photography. Their brains worked more efficiently, like younger brains, compared to a group that didn’t do these activities.
Other studies show that learning and staying engaged help protect our brain’s size and memory centres. In 2023, a Swiss study found that doing music for six months improved memory and made our brains more flexible and bigger.
Our brain’s ability to change and reorganize itself is called neuroplasticity. It helps us become more efficient at things. Doing challenging tasks builds new pathways in our brain that can offset the loss of function due to brain problems. We used to think that only young people could do this, but now we know that even as we get older, our brains can still change, just not as quickly.
We should think about cognitive reserve as more than just getting good grades in school or having a successful career, says Sommerlad. It’s like the result of keeping your brain active throughout your life, and it’s not just about education – although that’s what we’ve studied the most. Other things also matter, like living a healthy life, staying physically active, socializing with others, and doing mentally challenging activities. There isn’t one magical thing that boosts cognitive reserve, says Grundy.
But, how does our brain stay strong against dementia? It all comes down to one important thing: synapses.
In recent years, scientists have learned that Alzheimer’s disease is related to the loss of synapses. These synapses are the connections made by little branches (dendritic spines) that come out from our brain cells to connect with other brain cells. The density of these little branches is crucial for memory and learning. Here’s the key insight: some people’s brains, even if they have Alzheimer’s disease in there, still have good synapses, and they can think clearly. “The more synapses you have, the better you can fight Alzheimer’s disease,” says Patricio Opazo at the University of Edinburgh.
It’s not just about having more synapses from the start; our brains have a way to protect themselves. Jeremy Herskowitz at the University of Alabama at Birmingham thinks our brains can repair themselves if something bad happens, like Alzheimer’s disease building up. “The brain has its own way to fix things and keep working well,” he says.
Some interesting new research is showing how this fixing process works. Those little branches can be of two types: thin ones that are good for learning new stuff and mushroom-shaped ones that are better for keeping long-term memories. People with thinking problems from Alzheimer’s disease have fewer of the thin branches, but people who think clearly have more of them, even when they have Alzheimer’s in their brains.
What’s even more surprising is that the thin branches are longer in people with good thinking skills, which Herskowitz says is a big deal. Longer thin branches seem to help protect against Alzheimer’s disease. Plus, this research has found some things that control the number and length of these branches in our brains, which might help as a treatment.
One of these things is neuritin (NRN1), a special protein that brain cells release. NRN1 seems to help our brains fight Alzheimer’s disease. They saw this in a study of older Catholic brothers, nuns, and priests who agreed to have their brains studied after they passed away. When Herskowitz and his team looked at the results of these people’s tests, they found that those with higher levels of NRN1 in their later years had better thinking skills and more of the thin branches. “It’s like a vitamin for brain cells,” he says. They also discovered another protein called Twinfilin-2 that influences the length of these branches.
But how do these things help make our cognitive reserve stronger? The idea is that activities that make our brain work, like reading, socializing, and staying mentally active, can raise the levels of special proteins such as NRN1. These proteins help create new connections between brain cells or keep the ones we have in good shape. It’s a bit like how exercising makes your muscles stronger. If you keep using your brain, you keep it strong. If you stop, the connections between your brain cells might disappear, even without Alzheimer’s disease.
It’s still early days, but Herskowitz thinks that one day we might be able to take NRN1 as a supplement to support our brain and protect it from Alzheimer’s disease and dementia. This would be a different approach from the current focus, which is mainly on getting rid of plaques and tangles in our brain cells.
Other experts agree with this idea. Instead of just trying to get rid of the problems, we should boost the brain’s own defences against these issues, like fixing and rebuilding connections between brain cells, says Opazo.
It’s important to know that having a strong cognitive reserve can delay the time when thinking problems start, but when the problems do come, they might get worse faster, says Stern. That’s what happened to my mom, who was very smart and stayed active until she had a stroke. She could speak both English and French and loved doing challenging crossword puzzles.
For me, I’ll keep adding to my cognitive reserve each day, whether by writing articles, staying mentally active, or playing my Yamaha Keyboard. I hope that our new knowledge about how mental effort builds connections between brain cells will lead to new ways to protect my brain as I get older.
Reference: New Scientist Magazine 21 October 2023