Many people tend to describe aging as what happens when we reach a certain age and our minds (especially our memory) stop functioning as they used to.
“It’s part of the aging process, so there’s nothing we can do about it,” some say.
But that's not the case.
The brain can keep pace with bodily functions as we age, as long as we take proper care of it.
If you want to maintain a sharp mind as you age, you need to take immediate action and not leave it to chance.
Changing your lifestyle habits is one of the most immediate steps you can take.
One study supporting this involved having participants scan their brains with magnetic resonance imaging (MRI), then having them change their lifestyle habits. The participants then had their brains scanned again about six months to a year later to see if any changes had occurred.
Then, surprisingly, the brain appeared to have become younger than before.
(The lifestyle habits they adopted are detailed in the back of the book.) It's as if they were put into a time machine.
--- From "Part 1 | How Old Is Your Brain?"

Dr. Nedergaard wanted to know how the injured brain heals itself.
And we investigated what role sleep plays in the recovery process.
The subjects who participated in the experiment were encouraged to sleep, and while they were sleeping, they experienced a surprising phenomenon that made them feel as if they were watching a horror movie.
While the subjects slept, their brains shrank to a whopping 65 percent of their normal size! As they shrank, their brains began vibrating vigorously in a dynamic rhythm.
Additional research has shown that as the brain shrinks, waste, toxins, and other toxins that are stored within brain cells are compressed and expelled, creating more space for them to escape.
As the brain continues to shrink, the compressed waste collects in the empty spaces created by this process, and fluid from the spinal cord flows into the brain and washes it clean.
--- From "Part 1 | When your immune system is weakened, your brain becomes filled with garbage"

One interesting fact is that the heart has about 40,000 sensory neurons that transmit information to the brain.
Some researchers call these cells the "little brains" of the heart.
While more research is needed to elucidate the full extent of the information being conveyed, one thing is clear: heart health is one of the most important aspects of brain health.
(Omitted) Because the heart and brain are connected in this way, it is said that ‘a young heart helps the brain stay young.’
What happens in your heart can affect a range of conditions that put your brain at risk, from dementia to depression to anxiety.
Therefore, it is impossible to have a healthy, young brain without a healthy heart.
--- From "Part 1 | The Heart Sends a Warning to the Brain"

Surrounding yourself with optimistic people can lower your risk of Alzheimer's disease, dementia, and cognitive decline.
And if you are optimistic, it has a positive effect on your overall health.
Optimists tend to live longer, being 50 to 70 percent more likely to reach age 85 than non-optimists.
Research shows that optimism can be learned, and that it's easier to change if you think positively about your learning abilities.
In other words, if you are optimistic about learning to be optimistic, you are more likely to actually become optimistic.
So if you're a pessimistic person and think it's impossible to learn optimism, you probably never will.
When we believe we can do something, we become better at it.
--- From "Part 1 | The Heart Sends a Warning to the Brain"

Alzheimer's disease is intertwined with various factors, including inflammation, metabolic dysfunction, and vascular problems.
As these problems become complexly intertwined, brain cells age and become damaged, resulting in brain shrinkage.
When brain shrinkage occurs, memory declines significantly, and in patients with Alzheimer's disease and dementia, the hippocampus is particularly often damaged.
This is why dementia patients can remember events that happened decades ago but cannot remember new information.
--- From "Part 2 | The Brain Ages When There Are No New Memories"

An interesting fact is that not only what you eat, but also when you eat it can affect your risk of developing diabetes.
According to research presented at the 2021 Endocrine Society Annual Meeting, people who started eating before 8:30 a.m. had lower insulin resistance and blood sugar levels than those who ate their first meal of the day later.
A 2021 analysis published in Endocrine Reviews also found that restricting daily eating to less than 12 hours improved metabolic health.
However, the effectiveness of intermittent fasting is unclear.
Intermittent fasting is the practice of voluntarily alternating periods of fasting and eating throughout the day.
For example, some intermittent fasting methods involve eating all meals during an eight-hour window and not eating for the remaining 16 hours.
While some studies have shown that intermittent fasting can help manage and lower the risk of diabetes, another study presented at the European Society of Endocrinology found that fasting every other day could actually increase the risk of diabetes by causing problems with insulin regulation.
Because drastic changes in calorie intake and eating schedule can be dangerous, it's best to consult your doctor before attempting any form of fasting.
--- From "Part 2 | Eating Sweets Makes Your Brain Old"

Research results are often published that surprise scientists.
The study we will examine from now on is one of them.
Researchers followed 1.7 million people for 30 years to see if there was a link between the development of dementia and mental health disorders such as depression, anxiety, and bipolar disorder.
A study published in 2022 found that people with mental disorders develop dementia on average five years earlier than those without.
The researchers also analyzed cases of chronic diseases such as cardiovascular disease, stroke, diabetes, gout, chronic obstructive pulmonary disease, traumatic brain injury, and cancer.
As a result, they found that the risk of developing dementia was more strongly associated with mental disorders than with chronic diseases.

--- From "Part 2 | A Depressed Brain Ages Quickly"

Pete Sampras, one of the greatest tennis players of all time, holds the Grand Slam record, has won Wimbledon seven times, and is known for his powerful serve.
As for the tennis aspect, I'm not sure what made him such an elite player, but there's one thing that definitely contributed to his success.
Sampras always carried black masking tape with him as he traveled the world, crossing time zones.
The tape wasn't for the racket or to prevent injuries.
Every time Sampras entered a new hotel room, he covered all the electronic lights in the room with tape.
Everything that emits light is covered with black tape.
(Omitted) Why did I do that? Because I discovered that on days when I slept in complete darkness and woke up, I played better, was more focused, and felt more energetic.
At the time, people thought Sampras's actions were excessive.
But he knew that even the slightest light could wake him up.
I instinctively recognized what scientists had discovered through repeated research.
Artificial light disrupts our natural sleep cycle.
And sleep disturbances mess with the brain.
In other words, it's not just the amount of sleep you get, but how effective that sleep is.
--- From "Part 3 | Sleep ◇ Sleep heals the brain"

A 2022 study looked at whether even small amounts of light in the bedroom could affect your health.
The amount of light used in the study was so dim that it was impossible to read the book.
Participants reported that they did not notice the small light while they slept and felt that it did not disturb their sleep.
However, the results of these tests were different.
People who slept with a small light on had increased heart rate and insulin resistance throughout the night and into the next day.
Their nervous systems were activated overnight, which had negative effects on their cardiovascular and metabolic health.
The lesson here is that even if we don't notice the light, our bodies do.
--- From "Part 3 | Sleep ◇ Sleep heals the brain"

In other words, there's nothing wrong with walking more than 7,500 steps a day, but there aren't many additional health benefits.
Tracking your steps can be a great motivator, but taking a 40-minute walk three times a week is also a good idea.
One study found that people who followed this routine had larger hippocampi.
Not only did these walkers have improved memories, their brains also appeared one to two years younger than their actual age.
--- From "Part 3 | Exercise ◇ What Changes When You Walk 7,500 Steps a Day"

We need to accept loneliness as if it were a physical illness.
Physical pain is like our body sending us a warning that it needs to be cared for and healed.
In this way, loneliness is also a signal from the body that social interaction is necessary for brain health.

--- From "Part 3 | Emotions ◇ Ask About Others' Well-Being Every Day"