Brain evolution and the mystery of dementia: Experts discuss health implications

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Why is dementia on the rise despite the human brain getting bigger? The latest research reveals the causes and implications

Hello everyone. My name is Jon, and I'm a Japanese blogger who writes about self-improvement and lifestyle. Today, I'd like to talk about an interesting topic that has been making the rounds recently. Have you heard the news that "human brains are getting bigger"? While this may seem like a positive change, the reality is that dementia (a brain disease that impairs memory and thinking ability) is increasing worldwide. Let's explore this contradiction based on the latest research. First, let's start with the good news that increasing brain size brings.

According to a study published by UC Davis Health on March 25, 2024, the human brain is 6.6% larger, on average, in people born in the 1970s compared to those born in the 1930s. This change is accompanied by an increase in the brain's overall volume as well as its surface area. Researchers point out that this may increase "brain reserve" and reduce the risk of dementia. In other words, a larger brain is more resistant to the damage caused by aging and disease.

Meanwhile, the rise in dementia is a serious problem. According to a fact sheet updated by the World Health Organization (WHO) on March 31, 2025, approximately 55 million people worldwide suffer from dementia, with approximately 10 million new cases diagnosed each year. In the United States, a January 13, 2025, CNN report predicted that dementia cases will double by 2060. What is behind this increase? Why isn't dementia decreasing even though brains are getting bigger? Today, we'll unravel this mystery based on reliable sources.

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The fact that the human brain is getting bigger

First, let's take a closer look at the increase in brain size. A Medscape article published on March 27, 2024, based on research from UC Davis, reported that brain size has been increasing over time. The study analyzed head MRI (magnetic resonance imaging) data from over 3,000 people. Specifically, the average brain volume of those born in the 1930s was 1,234 cubic centimeters, but increased to 1,321 cubic centimeters for those born in the 1970s. The volume of the hippocampus (the part of the brain involved in memory) and white matter (collections of nerve fibers) also increased.

Why are brains getting bigger? Experts believe that improved nutrition, rising education levels, and medical advances are contributing factors. For example, better nutrition in childhood promotes brain development, the effects of which persist into adulthood. A September 24, 2025, article by mindbodygreen highlighted this change as "good news" that could improve brain health and reduce the risk of dementia. In fact, an April 2, 2024, article by New Atlas also pointed out that larger brains in younger generations may reduce the risk of Alzheimer's disease (a major form of dementia).

Similarly, a March 26, 2024 article in Futurism states that larger brains may help prevent dementia. Based on this information, it seems that increased brain size is a positive evolutionary outcome. However, we cannot be all happy. Next, let's face the reality of the increasing incidence of dementia.

The main reasons for the increase in dementia

Why is dementia on the rise even though brains are getting bigger? The key lies in an aging society and changing lifestyles. According to the Mayo Clinic's June 7, 2025 update, the primary cause of dementia is age-related changes in the brain, with cerebrovascular disease (a condition in which blood vessels in the brain become blocked) and Alzheimer's disease accounting for the majority of cases. WHO data lists high blood pressure, diabetes, obesity, smoking, and lack of exercise as risk factors for dementia. These are closely related to modern lifestyle-related diseases.

A mindbodygreen article explains that while a larger brain partially offsets the risk of dementia, the aging population is driving up the overall number of patients. For example, in the United States, the number of people over 65 continues to grow, driving up the incidence of dementia. According to a CNN report, as of 2025, approximately 670 million people have dementia, with the number predicted to reach 1,400 million by 2060. Additionally, posts on X (formerly Twitter) have cited psychiatric drugs, vaccines, stress, and excessive alcohol use as possible causes of dementia, but these are personal opinions with limited scientific evidence. Reliable research shows that lifestyle factors play a major role.

Furthermore, a September 19, 2025, post by X pointed out that the decrease in brain volume was due to alcohol and stress. In the Japanese context, a March 30, 2024, post in Nazology raised the topic of how larger brains increase resistance to dementia. Meanwhile, a July 21, 2025, post by psychiatrist Shion Kabasawa warned that a relaxed lifestyle after retirement could lead to a lack of brain activation, increasing the risk of dementia. Taken together, while the increase in brain size is a positive, it appears that modern stressful lifestyles and unhealthy habits are outweighing it.

Health impacts of increasing dementia and preventative measures

The rise in dementia affects not only individuals but society as a whole. Economically, it increases nursing care costs, with the WHO predicting global costs could exceed $2 trillion by 2030. Mentally, it impairs the mental well-being of patients and their families. A mindbodygreen article points out that while brain enlargement supports memory and cognitive function, inflammation and insufficient blood flow exacerbate dementia. X's post also cites poor gut health and brain inflammation as possible causes.

So what can you do to prevent this? Here is a list of preventative measures that are useful in everyday life, focusing on those that are easy for beginners to adopt:

Exercise regularly: Aim for 150 minutes of aerobic exercise (walking, jogging, etc.) per week to improve blood flow to the brain, which studies have shown to reduce the risk of dementia by 20-30%.
A balanced diet: A Mediterranean diet (high in vegetables, fish, and nuts) is recommended. Antioxidants help reduce inflammation in the brain.
Get enough sleep: Get 7-9 hours of quality sleep each night. Lack of sleep accelerates brain aging.
Social interaction: Talking with friends and engaging in hobbies stimulates the brain. Loneliness increases the risk of dementia.
Manage stress: Maintain your mental well-being through meditation and yoga. Chronic stress can cause your brain to shrink.
Regular health checkups: Check your blood pressure and blood sugar levels. Early detection leads to prevention.

These habits are also beneficial from a personal development perspective. For example, making exercise a regular part of your routine can increase your productivity. However, please note: this article is for general information only and is not medical advice. If you experience symptoms of dementia, be sure to consult your doctor. Professional guidance tailored to your individual health condition is required.

Implications for the future and the latest research trends

As of 2025, the latest research is focusing on digital health interventions. A paper published in Frontiers around August 2025 (three weeks ago) conducted an economic evaluation of digital tools for mild cognitive impairment (MCI, a precursor to dementia) in Canada, demonstrating promising preventative effects. Additionally, an NIHR event on September 7, 2025, discussed the future of brain health and dementia prevention. These findings suggest that prevention using AI and apps may become more widespread.

In a September 19, 2025, post, X emphasized the importance of a diet that suppresses brain inflammation to slow the progression of dementia. Another post (September 23, 2025) pointed out that a decrease in gray matter in the brain affects memory and emotions. Overall, the prospect of larger brains offers hope, but preventative lifestyle changes are essential.

Summary: Living a life that makes the most of brain changes

The fact that the human brain is getting bigger is good news as it reduces the risk of dementia. However, the number of patients is increasing due to aging and unhealthy habits. By understanding the causes and implementing preventative measures, we can build a healthier future. Why not try making small changes to your habits today?

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Even though the brain is getting bigger...Unraveling the mystery behind the increase in dementia!