Is “Retirement Makes You Senile” Outdated?

An AI Analysis of 10,000 People in 19 Countries Reveals the Smart Way to Retire and Keep Your Brain Young

“Won’t I age rapidly once I retire?”
“Does leaving work cut me off from society and increase my risk of dementia?”

You may have heard concerns like these before. In fact, many developed countries, including Japan, are promoting policies that encourage people to work longer for the sake of their health.

However, a groundbreaking study published in 2024 challenges this common belief.

Researchers led by Koryu Sato at the University of Tokyo analyzed data from nearly 12,000 individuals across 19 countries using machine learning. Their study, titled
“Heterogeneity in the association between retirement and cognitive function: a machine learning analysis across 19 countries,” reveals a surprising truth about retirement and brain health.

---

1. Why Has “Retirement Is Bad for the Brain” Been So Widely Believed?

Previous studies have produced mixed results. Some suggested that memory declines after retirement, while others found the opposite. Even scientists could not agree.

Why was there so much confusion?

The problem lies in a statistical trap—misleading averages.

The Hidden Group: “People Who Retired Because Their Health Was Declining”

When we simply compare retirees with people who are still working, retirees often show lower cognitive scores. But this does not mean retirement caused the decline.

Many people retire because their health or cognitive function has already started to worsen. This creates a reverse causality problem.

In this new study, researchers combined economic methods with an AI technique called a causal forest, carefully removing this bias. Once they did so, a very different picture emerged.

---

2. The Main Conclusion: Retirement Improves Cognitive Function on Average

The AI analysis reached a clear conclusion:

People who retired scored 1.348 words higher on memory tests than those who continued working
(equivalent to 0.42 standard deviations).

This is not a small effect. In public health research, an improvement of 0.2 standard deviations is already considered meaningful—for example, after educational or lifestyle interventions.

In other words, the cognitive benefit of retirement is remarkably strong.

Why Might Retirement Rejuvenate the Brain?

The paper suggests three main mechanisms:

1. Relief from Job Stress
   Chronic work stress harms the hippocampus, a brain region essential for memory. Retirement removes this constant pressure.
2. Better Sleep and Quality of Life
   Without commuting, deadlines, or work-related anxiety, the brain gets more time to recover.
3. More Time for Health-Promoting Activities
   Retirees can invest time in exercise, hobbies, learning, and social interaction—all known to support brain health.

---

3. Winners and Losers: Who Benefits Most from Retirement?

The most innovative part of this study is that it shows retirement does not affect everyone equally.

The researchers divided people into five groups (Q1–Q5) based on how much their cognition changed after retirement.

Q5: People Whose Brains Improve Dramatically After Retirement

Common characteristics:

• Gender: Female
• Education & Wealth: Higher education and financial security
• Occupation: Clerical, professional, or part-time work
• Health: Good health and regular exercise before retirement
• Countries: Denmark, Greece, and others

Q1: People Who Gain Little (or May Decline)

Characteristics associated with poorer outcomes:

• Gender: Male
• Economic Status: Lower income or fewer assets
• Occupation: Manual labor, self-employed, physically demanding jobs
• Health: Hypertension, diabetes, depressive symptoms before retirement
• Countries: Estonia, France, and others

---

4. Why Do These Gaps Exist? An Economic Explanation

The authors explain these differences using the Grossman model from health economics.

When you retire, you trade money for time.

• People with financial security can use their new time for health investments: exercise, nutritious meals, social activities, and intellectual hobbies.
• People under financial stress may spend that time worrying about money, limiting their ability to invest in their brain.

For former manual workers, retirement can also mean losing their only source of physical activity, which may negatively affect cognition unless replaced by intentional exercise.

---

5. How to Prepare for a Brain-Healthy Retirement—Starting Today

The most important lesson from this research is clear:

Your cognitive health after retirement is largely determined by how you live before retirement.

Here are four practical steps you can start now:

1. Build Exercise Habits Outside of Work
   Physical activity done by choice benefits the brain more than work-related movement.
2. Control Chronic Conditions
   Poorly managed hypertension or diabetes reduces the benefits of retirement.
3. Develop Meaningful Uses of Time
   Don’t wait until retirement to find hobbies, volunteer work, or learning communities.
4. Know Your Ideal Timing
   A uniform extension of retirement age is not always optimal. Consider your finances, stress level, and health when planning your exit.

---

6. Final Thoughts: Designing the Right Exit in the 100-Year Life Era

For a long time, “working until you drop” was seen as the ideal way to stay healthy.

But scientific evidence now suggests something different:
stepping away from work at the right time and investing in self-care may strongly protect—and even rejuvenate—your brain.

Retirement is not “the beginning of the end.”
It can be a chance to reboot your brain.

Whether your future free time becomes a source of anxiety or a powerful investment in cognitive health depends on the choices you make today.

---

Study Information

Title: Heterogeneity in the association between retirement and cognitive function: a machine learning analysis across 19 countries
Authors: Koryu Sato, Haruko Noguchi, Kosuke Inoue
Journal: International Journal of Epidemiology (2024)