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Could you introduce yourself and tell us why you pursued public health?

When I was a medical student aiming to become a neurosurgeon, I decided to visit a place very different from Japan and traveled to Bangladesh. There, I experienced intense culture shock. Despite the existence of a national cardiology hospital built with JICA’s support in the capital, Dhaka, the hospital was nearly empty, while many patients lay outside on the ground just in front of the hospital, in a scene resembling a battlefield.
This was because medical costs had to be paid entirely out-of-pocket. The poor simply couldn't afford treatment. That reality shocked me deeply. Although I stayed in Bangladesh for only about ten days, the experience changed my entire vision for the future. After graduating from university, I decided to pursue public health.
Unlike clinical medicine, which focuses on one-on-one relationships between a doctor and a patient, public health involves one-to-many relationships, with medical professionals working to improve the health of entire communities. In impoverished regions like developing countries, you can't help individuals alone—you must address collective issues such as nutrition and the environment to improve public health. I realized the importance of that approach firsthand.
After returning to Japan, I started a student group called the 'International Health Study Group' with my classmates. At the time, we didn’t have the internet, so information was limited. I remember writing letters to WHO and UNICEF asking for materials on international health. They would arrive months later, and we would study primary health care for the poor.

Did you go directly into public health after graduation?

Yes. Medical students study all specialties, and after taking the national licensing exam, most choose a clinical field. I was the only one in my class to pursue public health. Believing field experience was essential, I joined the Hokkaido Government to work at a local public health center. Public health centers, as highlighted during the COVID-19 pandemic, handle a wide range of responsibilities supporting community health.

Can you tell us about your experience at the public health center and your subsequent career in international cooperation?

I was appointed director of a health center at a young age—one of the youngest in the country, as Japanese law requires directors to be medical doctors.
I was assigned to a rural town in Hokkaido, working directly with mayors, city council members, and other local leaders—often a generation older than me. We tackled local issues head-on, such as hospital management and population aging. It was rewarding and challenging for me.

You also worked in Brazil through international cooperation?

I had initially worked in the Philippines and hoped to continue my work in Asia. But on my first day at the National Center for Global Health in Tokyo, my boss told me, 'I order you to go to Brazil.' Honestly, I knew nothing about Brazil beyond soccer and Carnival, but I went there. I was assigned to a university in Recife, a major city in northeastern Brazil, where I led the JICA 'Healthy City Project.'

What does the 'Healthy City Project' mean specifically?

A Healthy City means different things to different people, so we began by defining our goals, planning what we hoped to achieve within the project period, and designing the budget and activities from scratch.

Were there language or cultural barriers?

Yes—I didn’t speak Portuguese, so I had to learn it quickly. I negotiated in my poor Portuguese with help from professional interpreters. Brazil is a country with huge disparities, where the rich and poor live side by side.

So the issues were more social than medical?

Exactly. The root causes of poor health in Brazil weren’t medical, but stemmed from poverty, lack of education, discrimination, and unemployment. These are known as the social determinants of health. Traditional medical approaches alone weren’t enough. Health isn’t just about vaccines or drugs—it’s about the entire social structure.

It sounds like your work went beyond conventional public health.

Yes. In 2008, the WHO Commission on Social Determinants of Health emphasized how social structures affect health. Our work in Brazil was a practical application of that philosophical strategy.

What were conditions like for workers in the field?

Many sugarcane workers lacked education and handled toxic pesticides bare-handed for 12 hours a day. If they got sick from the chemicals and took days off, they lost wages. The conditions were brutal.
To protect them, we educated them on safe pesticide use, lobbied companies to provide gloves through local governments, and improved workplace conditions. We also established rules for seeking medical care and facilitated collective bargaining with companies through municipalities. In a way, I was more like a social reformer than a physician.

You were addressing root causes while staying close to the people.

Exactly. That, to me, is what public health truly is. Rather than just clinical treatment, it’s about rethinking health starting from people’s living conditions. I realized we needed to shift from just medical interventions like vaccines and drugs to social interventions that address behaviors, environments, and education. Through this experience, I realized the importance of scientific basis and evidence, and decided to study epidemiological statistics again.

Is that why you became a university professor?

I was over 40 years old when my former mentor invited me to join the university. Since then, I’ve focused my research and teaching on global health—what we used to call 'international health.'

What’s the difference between 'international health' and 'global health'?

The old idea of international health was top-down: developed countries helping developing ones. But since the introduction of the Millennium Development Goals (MDGs) in the 2000s, a new perspective called 'global health' has gained widespread attention. This is about shared global health challenges that all countries, rich or poor, address together.

So it's no longer about giving and receiving aid?

Exactly. Issues like maternal and child health, environmental pollution, and global warming affect developed nations too. Global health is about tackling shared problems on equal footing. That’s what I want my students to understand.

Why did you shift your focus to elderly care?

Previously, I had engaged in infectious diseases prevention and maternal and child health—areas where Japan had successfully improved post-WWII and could offer valuable expertise. But now, aging is emerging as a critical issue in developing countries too. That led me to think that it is important to teach university students about elderly care, and I shifted my area of expertise accordingly.
Japan, as a global front-runner in population aging, has a wealth of experience, but our systems are costly. We must find affordable ways to share our knowledge internationally.

What are low-cost older adult care strategies?

There are two key approaches. The first is prevention, which means preventing older people from becoming dependent on care. To be precise, delaying the onset of care dependency is crucial. Under the concept of preventive care, we aim to keep people as healthy as possible. The second is shifting from facility-based to home-based care. Japan introduced long-term care insurance in 2000, but it’s becoming financially unsustainable. We need to strengthen systems for receiving care at home.

But isn’t that shift challenging?

It is challenging. Facility-based systems are already in place, and shifting to home care isn’t easy. There are financial and social burdens on families. Actually, in the 1980s, we saw the social issue of 'caregiver burnout,' and even now, about 100,000 people quit their jobs annually due to caregiving.

So maintaining vitality while reducing burdens is the key.

Exactly. We’re now focusing on the prevention of 'frailty'—a transitional phase between healthy aging and care dependency. If identified early, people can often recover. Surveys by the national government and Tokyo found nearly half of seniors over 65 are either frail or pre-frail.

How do you detect and intervene in frailty?

Our research is addressing frailty prevention now. Previously, assessments were fragmented—muscle strength, oral function, etc. But humans are multidimensional. We’re developing an AI/IT-based tool to evaluate physical health, nutrition, social engagement, cognition, and mental state holistically.
We collected data in Suginami. Ultimately, we aim to create a comprehensive evaluation tool. We are developing a cost-effective system that can be used even in developing countries in the future.

What are your concerns or priorities for the future?

I tell my students that the Nankai Trough Earthquake is likely to occur within 20 years. Government predictions support this, and it could devastate Osaka and Nagoya. Historically, Mt. Fuji has erupted after such earthquakes, and modern projections estimate 5cm of volcanic ash in Tokyo and 10cm in Yokohama.

Would just 5cm of volcanic ash really cause that much disruption?

Modern society depends heavily on infrastructure and computers. Just 5cm of ash could paralyze water, transportation, communication, and power systems. We can’t just say, “we’ll manage somehow.” Our densely populated, tech-reliant society is far more vulnerable than it was during the Edo period.

What do you want students to take away from this?

They need to prepare to protect their lives—and think about how they’ll support society’s recovery afterward. It could be as disruptive as post-WWII. We must imagine and prepare now for rebuilding society after such a disaster.

You're not trying to scare people, right?

No. I want young people to confront reality and prepare with imagination. That’s the power they’ll need to survive. I may not be alive when the time comes, but I want students to have opportunities to think about how they will survive in the future.
Right now, I’m working on developing systems that allow seniors to live healthily without spending money. If a disaster like the Nankai Trough Earthquake occurs, health and nursing care insurance may collapse. We need to prepare systems for people to survive independently.

And this applies beyond Japan, right?

Yes. The UN defines aging societies as follows: When the aging rate (the percentage of people aged 65 or older) exceeds 7%, it is called an “aging society”; when it exceeds 14%, it is called an “aged society”; and when it exceeds 21%, it is called a “super-aged society.” Many developing nations in Asia and Latin America are rapidly reaching these levels.

So they’ll face the same issues eventually?

Exactly. Thailand’s aging rate recently exceeded 14%, and it became an aged society. But its per capita GDP is around $7,000—compared to Japan’s $40,000 when it reached the same level, which means that Thailand, with an economy less than one-sixth the size of Japan's, is facing the same problems as Japan. Thailand probably won’t be able to introduce a system like long-term care insurance. And the same applies to its neighboring countries.

What have you seen firsthand in these countries?

I was shocked when I visited an older person’s home in Thailand. Diapers weren’t changed, and the smell was overwhelming. Traditional stilt homes in rural Thailand housed seniors beneath the main living area—essentially where animals lived. There was no sanitation or privacy. I’ve seen the same in Mexico and Brazil. A 'tsunami of aging' is just approaching many developing nations.

So the wave is clearly visible now?

Yes, but many countries are still metaphorically 'drinking beer on the beach'—unaware or unprepared for the coming crisis. That’s why we must build affordable, sustainable, and inclusive social systems for elderly care worldwide. This is the greatest challenge public health faces today.