It's not just the sushi – and it's definitely not the sake. Japan has the highest life expectancy in the world but the reasons, says an analysis, are as much to do with equality and public health measures as diet.

A baby girl born in Japan today can expect to live to 86 and a boy to nearly 80. But it has not always been so.

According to a paper in a Lancet series on healthcare in Japan, this is a rise of 30 years from the expected lifespan in 1947. While Japanese diet has contributed, it is far from the only factor.

The remarkable improvement in Japanese health began with the rapid economic growth of the late 1950s and 1960s. The government invested heavily in public health, introducing universal health insurance in 1961, free treatment for tuberculosis and cutting childhood deaths through vaccination and treatment of intestinal and respiratory infections.

Following the control of infectious diseases, Japan tackled its high death rate from stroke with salt reduction campaigns and the use of drugs to control blood pressure.

But beyond the government's initiatives, there are attitudes and cultural practices among the people of Japan that have also helped, says the article by Professor Kenji Shibuya, of the department of global health policy at the University of Tokyo, and colleagues.

"First, Japanese people give attention to hygiene in all aspects of their daily life," they write. "This attitude might partly be attributable to a complex interaction of culture, education, climate [eg humidity, temperature], environment [eg having plenty of water and being a rice-eating nation] and the old Shinto tradition of purifying the body and mind before meeting others.

"Second, they are health conscious. In Japan, regular check-ups are the norm. Mass screening is provided for everyone at school and work or in the community by local government authorities. A systematic check-up of the whole body, referred to as a human dry dock, is another type of health screening, which is popular amiong business people - they stay at clinics or hospitals for several days to undergo thorough physical examinations.

"Third, Japanese food has a balanced nutritional benefit and the diet of the Japanese population has improved in tandem with economic development over the past five decades."

The downside of Japan's success in keeping its people healthy is that the population is unbalanced and becoming more so. At the moment, 23% of the population is over 65 but by 2050, that will rise to 40% in a population shrinking from 127 million to 95 million. Other problems include drinking and smoking among overworking business people and a high suicide rate partly attributable to rising unemployment. Unless these issues are tackled, the paper suggests, Japan could lose its position at the top of the longevity table.