The first thing Koji Saito does when I walk through the front door of his home in Sakaemura is laugh -- a raucous guffaw that leaves his eyes glistening with moisture. Minutes later, he is at it again as we take our places on the tatami mat floor of his living room while his wife and daughter-in-law pour cups of steaming green tea.
Saito has plenty to be happy about. At 88, he is the picture of health, the only obvious concession to age a hearing aid in his left ear. He is still fit enough to ride his motorcycle, at speeds that horrify his family, up the hill every morning after breakfast to perform the backbreaking task of pulling weeds from the deep, dark sludge of his rice paddies.
Should he ever feel the need for companionship, unlikely though that is for a married man who lives with three other generations of his family, he needn't venture far. In Sakaemura, a village of 2,500 people hidden among the mountains of Nagano prefecture, north-west of Tokyo, almost half of the inhabitants (1,061 people), are over 65.
The men of Nagano prefecture live longer than those elsewhere in Japan. In 2000, according to the health ministry, they could expect to live until they were almost 79, while the women, with an average life expectancy of 85, ranked third nationally.
Similarly impressive statistics have been recorded across Japan, where life expectancy has increased dramatically during the past 80 years. In 1935, life expectancy was about 45. By 1950, that figure had risen to 60. Today it stands at 85 for women and 78 for men.
Japanese women live, on average, over five years longer than those in the US. Japanese men typically have more than four years on those in the US. The number of centenarians in Japan has doubled in the past five years and now stands at just over 20,000.
So what is behind the phenomenon of Japanese life expectancy? Most theories have centered on the low-fat diet of fish, rice and soy products such as tofu. But diet is just one of the factors that combine to make for a longer, healthier life. While few scientific studies point to definite explanations for Japan's long-living population, there is no shortage of possibilities. Universal health insurance, achieved in the early 1960s, undoubtedly has an impact, as does the generous state pension scheme. In Japan, poverty in old age is rare.
Education also plays a role.
"There is no illiteracy, even among people aged 70 and over," says Takao Suzuki, vice-director of the Tokyo Metropolitan Institute of Gerontology. "They are very sensitive about information on health problems, so I would say education is one of the important factors."
Suzuki says the benefits of the traditional Japanese diet have been made possible by economic development. Before the Second World War, the average intake of animal protein was less than 7g a day, but has risen to a near-ideal 40g, along with a similar level of vegetable protein. While cholesterol intake is rising, it has not reached the levels seen in the west, where there are unprecedented levels of obesity.
The nanny state, guaranteed to cause hyperventilation on the British right, is alive and well in Japan. The elderly are an important part of "Healthy Japan 21," a collection of 70 public health targets the health ministry wants to achieve by 2010. They include reducing salt intake (from the current 13.5g to 10g a day) by persuading people to cut down on salty staples such as miso soup and pickled vegetables.