Japan has ranked first in "healthy life expectancy," followed by Singapore, in the 2013 study of 188 countries released this week by the British medical journal Lancet.

Japanese men scored 71.11 years and Japanese women 75.56 years on the list measuring the probable period of life where people are expected to live on their own without the aid of nursing and without getting so sick that their daily activities are interrupted.

Singapore ranked second, averaging 72.1 years for men and women, followed by Ireland, Iceland and Cyprus, according to the study conducted by a team of researchers from the University of Washington and other institutions.

The study also estimated overall life expectancy, putting the Japanese male population's figure at 80.05, above 80 years for the first time, and women at 86.39.

The team also produced data for 1990, saying average life expectancy has increased from around 65 years in 1990 to about 71.5 in 2013 globally, while healthy life expectancy has increased from just below 57 years to slightly above 62 in the period, attributing the increases to progress in fighting infectious diseases such as AIDS and malaria.

For most of the 188 countries studied, changes in healthy life expectancy between 1990 and 2013 were "significant and positive," the researchers said. But in many — among them Belize, Botswana and Syria — healthy life expectancy in 2013 was not much higher than in 1990.

Healthy life expectancy takes into account both mortality and the impact of nonfatal conditions and chronic illnesses such as heart and lung diseases, diabetes and serious injuries. Those detract from quality of life and impose heavy costs and resource burdens.