The rapid progress made by medical science has without doubt served to mitigate physical and mental pains of those suffering from illnesses, and to extend the span of healthy life. Indeed, great strides have been made during the past two to three decades in pharmaceuticals, medical equipment and techniques for surgical operations in the prevention and cure of cancer, heart diseases and cerebral vascular illnesses, which together account for nearly 60 percent of the causes of death in Japan.

Those in the age bracket from 15 to 64, known as the productive age population, can now rest assured of performing their duties and enjoying their lives with no less physical and mental capabilities than their able-bodied colleagues even if they suffer from serious illnesses or accident-related injuries, as long as they receive proper medical treatment and are cared for under appropriate convalescent programs.

As of 2014, children of up to 14 years of age accounted for 12.7 percent of Japan's total population, the productive age population in the 15-64 age group 61.3 percent and senior citizens (age 65 and up) 26.1 percent.

But the National Institute of Population and Social Security Research estimates that these figures will change to 9.1 percent, 50.9 percent and 39.9 percent, respectively, by 2060, ushering in an age of an amazingly low number of children and equally an amazingly large population of elderly people. It is also estimated that the total population will dwindle from 127 million to 87 million during the same period. This means that by 2060, each member of the productive age population will have to support one child or one senior citizen.

Moreover, with 97 percent of children attending high school, 50 percent of high school graduates going on to universities and 50 percent of married women becoming housewives, the labor force participation ratio (the ratio of actual workers, both employed and unemployed, to the overall size of the productive age population) stood at a mere 55.5 percent in 2010 — drastically low when compared with the advanced nations of Western Europe and North America. If this trend continues, only a quarter of the Japanese will be working in 2060.

What impact would the progress of medical science have on the composition of the population? As stated above, such progress will serve to minimize a decline in the productive age population as caused by illnesses as well as a fall in the labor force participation ratio resulting from diseases and injuries, ultimately contributing to economic growth by putting the brakes on the shrinking of the labor force.

The other side of the coin is that the progress of medical science is certain to drastically reduce the mortality rate of the elderly, raising the percentage of the senior citizens within the total population.

Assuming that by the middle of the 21st century, tissue-engineering technologies will be in place to regenerate most internal organs, the life expectancy of the elderly is certain to become endlessly longer, boosting the percentage of those 65 years of age or older from 40 percent forecast for 2060 to nearly 50 percent of the total populations.

It seems to be a good thing that a dramatic fall in the mortality rate will slow down the shrinking of the population. But it must be asked whether it will be possible to sustain such a hyper-aging society in which one out of every two persons is 65 or older and every fourth person is at least 85.

According to the Ministry of Health, Labor and Welfare, about 60 percent of those at the age of 85 or older today need assistance or care. Since the aging of brains, muscles and bones is unavoidable, about 15 percent of the total population would require such assistance or care.

Since there will be a limit to the number of people to engage in the assistance and care of the elderly, these services would inevitably have to be carried out mainly by immigrants from Southeast Asia, robots and technologies related to information and communications. But advances in medical science may make it possible to prevent dementia and aging of muscles and bones.

In a ultra-high age society, costs for social security will increase dramatically. In the government's general account budget for the current fiscal year through next March, about ¥30 trillion, or 32 percent of the total, is earmarked for social security such as pensions, medical and nursing care services, and other welfare measures.

Since some of the costs of medical and nursing care services will have to be shouldered by the government, expenses related to social security could come close to 50 percent of the general account budget in an ultra-high age society.

There are only two ways to finance the huge costs of medical and nursing care services. One is to raise the consumption tax rate to 20 percent as a source of revenue to cover social security. The other is to make individuals bear all the costs for receiving advanced but expensive medical treatment, including tissue engineering.

If the latter of these two alternatives is chosen, money will determine whether one will live or die. One medical scientist has confided that in the not so distant future, it would become possible to extend your life span by one year if you're prepared to pay ¥10 million.

Nomura Research Institute defines households possessing net financial assets in excess of ¥500 million as the "ultra-high-net-worth" class and those whose assets range between ¥100 million and ¥500 million as the "high-net-worth" group.

But these two categories account for a mere 1.4 percent of all households in Japan. This would mean that only 0.5 percent of all households, which are classified as upper "high-net-worth" or above, would be able to live to be 100 or older by enjoying the full benefit of advanced medical technologies.

In reality, the progress made in medical science would extend the life expectancy of wealthy elderly people to 100 or more while making no change to that of poor people in the same age group.

But one should not feel angered at the prospect of society moving into a stage where a disparity of wealth will lead to a disparity of life expectancy. After all, only five out of every 1,000 persons would be able to benefit from highly advanced medical science, and, moreover, people's opinions would be split right down the middle as to whether it would be a good thing to live to the age of 110 if you require constant care.

Takamitsu Sawa is president of Shiga University.