India, Sept. 30 -- India has achieved one of the great public-health gains of the past century: we are living much longer. Life expectancy, around 40 years in the early years after Independence, is about 72 today. The gap with the United States, at around 79 years, has narrowed sharply.

But longevity creates a new challenge: How many of those additional years will be lived in good health?

WHO's latest comparable estimates put healthy life expectancy at 58.1 years in India, against 63.9 in the United States and 73.4 in Japan. Japan's achievement, therefore, is not simply longevity. It is healthy longevity.

India's latest National Family Health Survey, NFHS-6, shows why this matters. Nearly 31% of women and 27% of men aged 15-49 are over...