05/06/2013 10:44 pm ET | Updated Jul 06, 2013

What Is the Greatest Threat to Japan's Health?

It all started 20 years ago when I was doing my residency in a rural hospital in Chiba prefecture. During my post in the emergency room, I was shocked by a report I happened to read titled "World Development Report 1993: Investing in Health" by the World Bank.

The report examined the development of a rapidly-aging population and changes in disease trends across the world, based on a global health indicator analysis, the "Global Burden of Disease Study" (GBD).

Most importantly, it pointed out that "health care is an investment, and not always a cost."

I decided at once to go to Boston to meet with one of the lead authors, Chris Murray.

Chris and I soon hit it off. We both believed that a doctor's job was not only to cure a patient's disease. But more than anything, we both loved math, statistics and challenging conventional wisdom.

That meeting was the beginning of my long relationship with health care policy.

Exactly 20 years later in 2013, I have come full circle as I -- along with the collaborative research efforts of Chris and over 500 researchers worldwide -- have published the result of our multi-country analyses, "2010 Global Burden of Disease" in The Lancet journal and on the IHME website.

These results spanning multiple countries have had a much larger impact on various nations than the report 20 years ago. In countries such as England, China, and the United States, we have already begun to see policy changes at the government level.

One of the benefits of having results by country is the ability to simultaneously compare nearly 300 diseases and over 60 risk factors. In Japan, we are prone to focusing on the country's three leading causes of death (cancer, heart disease, and stroke), but we have not been looking at whether or not these three causes are in fact causing a burden as diseases.

As such, this leaves us unable to create effective health care policies.

According to our latest research, the greatest threat to the health of Japan was surprisingly lower back pain, which can lead to stroke, ischemic heart disease, pneumonia, and other musculoskeletal diseases. Suicide is also among the top 10 burdens to our national health. Another to watch is Alzheimer's disease. It first entered the top 10 in 2010 and is now ranked as the number 8 burden to the health of Japanese people. (In 1990, it ranked 23rd.)

Life expectancy minus the number of years spent afflicted by disease is called healthy life expectancy. Healthy life expectancy is the most compelling index to measure a country's level of health. Even if life expectancy of a country grows, I believe you cannot say that its health conditions are good if many of its people are bedridden or have mental health problems.

For the last 20 years, Japan has been ranked number one in the world with respect to both life expectancy and healthy life expectancy. That is something to be humbly proud of.

Japanese women's life expectancy rose from 82 years in 1990 to 85.9 years in 2010, while Japanese men also lived an average of 79.3 years in 2010, up from 76 years in 1990.

However, what we must pay attention to is healthy life expectancy. I believe it is more telling that Japanese women enjoy healthy lives for only 71.7 years, and men for only 68.8 years. In other words, one can say that most middle aged and elderly Japanese are living with some kind of disease.

Although Japanese food is widely praised throughout the world, traditional Japanese food is low in fat, but also high in sodium, and lacks nutrients from fruits, nuts, and whole grains. High blood pressure and smoking numbers continue to be high.

The problem of the elderly becoming bedridden is also serious. For affected families, the problem of who will care for the elderly is not only an economic problem, but also a psychological one.

Japan should not be complacent simply because of its high life expectancy. In order to combat unbalanced nutrition, mental health problems, smoking, and our aging population, I believe the time has come to make continuous strides from national policy to one's individual practice. And by doing so, we Japanese people can achieve true longevity.