Studies show that people who are regularly physically active can cut their risk of Alzheimer's in half. Why doesn't everyone take advantage of such an easily accessible remedy?

When Professor Linda Hildegard Bergersen first read about the effects of exercise on the brain, she thought:

“How can anyone not exercise?”

Especially because it's such an incredibly accessible "medicine."

Linda Hildegard Bergersen is a professor of physiology at the University of Oslo and a professor of aging and neurobiology at the University of Copenhagen.

“We’ve made dramatic changes to our lifestyle in a very short time,” she says, continuing:

“I was born in the 1960s and belong to a generation that walked, cycled, or skied to get to school. Today, a child who doesn’t participate in some form of organized sports risks sitting around all day.”

At least 20 minutes every day

The Norwegian Directorate of Health (a professional and regulatory body under the Ministry of Health and Care Services) recommends that we engage in a total of 2.5 hours of moderate-intensity physical activity per week. That is approximately 20 minutes a day.

Most people know that exercise reduces the risk of cancer and cardiovascular disease, but the fact that it also strengthens the brain and can help reduce the risk of Alzheimer’s probably comes as a surprise to many.

It is precisely this last point that gerontologist Linda Hildegard Bergersen is particularly interested in.

She knows that the brain is highly plastic—even as we age. But that means we can influence it ourselves—well into old age.

The hippocampus shrinks

One significant change in the brain is that the hippocampus shrinks as we get older.

The hippocampus is a region of the cerebrum that plays a crucial role in memory, learning, and spatial orientation.

“It’s a normal part of aging,” explains Linda Hildegard Bergersen.

“But when we take images of the brain, we see that this shrinkage occurs more slowly in people who are physically active. In these people, new, fresh blood vessels form in the brain tissue, specifically in the area where memory is located. New blood vessels allow the brain tissue to access oxygen and nutrients more easily. It gets more 'fuel.'“

Physical training and social training

It’s not just about making sure the brain gets the nutrients it needs. Researchers also know that physically active people generate new nerve cells in the brain.

The brain produces new brain cells throughout our lives, but this production declines as we get older.

“That’s why exercise alone isn’t enough as we approach age 60 or older. We also need to use our brains.”

Of course, we can sit down at the kitchen table with a crossword puzzle or Sudoku, but the best way to exercise our brains is when we’re with other people.

“One of the smartest things you can do is to be physically active with other people. That way, we get exercise, and our brains get the chance to be social,” explains Linda Hildegard Bergersen, who adds:

“This is how we generate a large number of new nerve cells in the brain.”

If exercise were a pill, we'd all take it

Ole Petter Hjelle, a physician and brain researcher, is also concerned about how few of us realize that exercise is practically medicine—and this applies to the healthcare system as well.

“When I talk about the solid, well-researched studies showing just how beneficial exercise is—not just for muscles and bones, but also for the brain—people are very surprised.”

“If physical activity were a pill, we’d all take it,” Ole Petter Hjelle told Videnskab.dk’s Norwegian sister site, forskning.no, in 2018.

The reason even healthcare professionals aren’t aware of all the benefits is that it’s a tool that hasn’t really found its way into doctors’ toolkits, he believes.

“When I was studying medicine, I had 140 hours of pharmacology and zero hours on physical activity as medicine. It’s not much better today. In the medical program in Oslo today, students have 45 minutes on this topic over the course of six years,” he points out.

- Why is that?

“There are probably several reasons, but I think one of the challenges is that there isn’t an industry behind it promoting exercise as a genuine treatment option, just as the pharmaceutical industry—naturally—does with medications,” says Ole Petter Hjelle.

How much exercise do we need?

Researchers all agree that exercise is good for you, but just how much exercise we need to boost our health and stay fit and healthy is another matter entirely.

In fact, researchers have been debating this for years. Perhaps it also has to do with the fact that we are all different.

In recent years, researchers have certainly become more aware that many medications should be tailored to each individual. Perhaps the same is true of physical activity and its effect on our brain health.

“It may well be that exercising three times a week is enough for one person, but that another person needs to exercise five times a week,” says Linda Hildegard Bergersen. She continues:

“We know that some people respond very well to exercise, while others don’t respond as well. Some of us take longer to get in shape than others.”

"It's important not to overcomplicate things," points out Linda Hildegard Bergersen, "because the most important thing is to get your heart rate up."

Does the effect improve with more exercise?

The question of how much exercise is needed to keep the brain healthy and fit in the most effective way is the subject of a major ongoing study in the United States.

Arthur Kramer, a professor at Northeastern University in Boston, has been studying the effects of physical activity on the brain for 30 years.

Around the world, the population is aging, and a daily exercise routine can make the difference between a frail and a healthy old age.

Arthur Kramer's research team has previously observed that problem-solving ability improves when people run or walk at a brisk pace.

But researchers know very little about how much exercise is needed. Does the effect improve if you are more active? Or is a little bit of activity enough? Researchers in Boston are currently studying this, according to svt.se.

Arthur Kramer tells the Swedish news channel that the way we view exercise today is somewhat similar to how we viewed smoking 20 years ago. We have gradually begun to understand how harmful a sedentary lifestyle is to our health.

It's never too late

"One of the most important messages he conveys to his patients as a doctor is that it's never too late to start," says Arthur Kramer.

“I have quite a few patients who have been very inactive and who think it’s no use now that they’re getting older. That’s wrong. It can yield tremendous benefits for the brain—no matter when in life you start.”

“The brain is perhaps the organ that benefits the most. Virtually all areas and functions of the brain are enhanced when we move. We become more alert. Our memory improves. We become more creative. We cope better with stress.”

It's hard to get up off the couch

Even though we’re constantly told how beneficial exercise is for both our bodies and our minds, many people find it really hard to get off the couch. And that’s not really surprising, according to Ole Petter Hjelle.

“Evolutionarily speaking, our brains have a tendency toward laziness. Our ancestors were physically active because they had to be. They had to flee from enemies and run to find food, but the rest of the time they stayed still to conserve energy, because they didn’t know when their next meal would come.”

“The brain wants us to conserve calories. And the brain we have today hasn’t fundamentally changed since the days when we were hunters and gatherers on the savanna. It remains programmed for laziness whenever we can get away with it. To overcome the lazy brain, he believes it’s a good idea to focus on the immediate benefits of exercise, and less on what happens in the long run.

“Many of the benefits are immediate; when we go for a walk in the fresh air, our mood improves, and much the same happens with our attention and memory.”

Discovered receptors for lactic acid

Of course, researchers are also interested in uncovering what actually happens in the brain when we are physically active. What is it that produces these positive effects?

Linda Hildegard Bergersen and her research team at the University of Oslo have shown that lactic acid plays an important role.

When muscles work intensely, this can activate a specific receptor for lactic acid, which in turn causes blood vessels to grow and increases the density of small blood vessels in the brain.

Such the formation of new blood vessels can help prevent the development of cognitive decline and age-related dementia. It simply keeps the nerve cells functioning properly.

The research findings were published in the journal *Nature Communications* in 2017, and the researchers also wrote an op-ed in *Aftenposten* that same year.

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