Japanese who smoke, are overweight and do not get much exercise tend to pay 40 per cent more for their healthcare costs than those without these risk factors, according to a long-term health ministry study.

The study was conducted on around 50,000 people in northern Miyagi Prefecture for a nine-year period, the longest time that such research has been done in Japan, according to the team led by Ichiro Tsuji, a professor of epidemiology at Tohoku University’s Graduate School of Medicine.

“Guessing from the results of the research, I would think unhealthy lifestyle habits have an (added cost) impact of 4 to 5 trillion yen ($A46-57 billion) on the entire healthcare costs,” Tsuji said

The team has proposed to the ministry that premiums for public health insurance policies should be determined according to prospective policyholder’s habits and health.

“We have now come to the point where we should be considering setting risk-based premium rates as done by private-sector life and medical insurance services, in addition to taking measures emphasising preventing sickness from the risk factors,” Tsuji said.

The team says payments into insurance policies and their coverage can be set according to the degree of risk a policyholder faces.

MPs are currently examining healthcare reform legislation that aims to curb medical costs topping 30 trillion yen per year.

The team began collecting data on average healthcare costs per month per person from January 1995 until December 2003. It involved those who subscribe to a public health insurance policy for the self-employed, retirees and others who are not covered by their jobs.

A group of people who had a history of smoking, were overweight beyond a certain level, and walked less than one hour per day paid on average Y29,272 ($A335) in medical expenses.

This was about 44 per cent higher than the Y20,376 ($A230) paid by those who did not have any of the three risk factors.

The gap varies among those people who have a combination of two of the three factors or have only a single factor - ranging from 7 per cent higher for those people who are either only overweight or do not exercise much to 31 per cent higher for those people who smoke and do little exercise.

The Ministry of Health, Labor and Welfare has been placing priority on early diagnosis and promoting healthy lifestyles to prevent against diabetes, stroke and cancer, which are associated with the three risk factors.