and Epidemiological Perspectives
NOREEN GOLDMAN AND SHIGESATO TAKAHASHI
The dramatic increase in Japanese longevity over the past several decades has received considerable attention from social and medical scientists ( Marmot and Smith, 1989; Morio and Takahashi, 1986; Okino, 1978; Ohno, 1985; Shigematsu and Nanjo, 1993 ). As shown in Table 8.1, life expectancies for Japanese men and women have more than doubled over the past century. During the past 40 years alone, life expectancy has increased by more than 15 years for men and by almost 20 years for women, reaching levels of 75.9 years for men and 81.9 years for women in 1990. A comparison of all national populations reveals that Japan has experienced the highest life expectancy in the world during the past decade.
Although the rate of improvement of Japanese life expectancy has begun to decelerate, it continues to exceed those in other low-mortality countries. These findings are illustrated in Figure 8.1, which presents estimates of life expectancy for Japan, the United States, and six European countries, each of which experienced greater longevity than Japan through at least the mid-1960s and several until 1980. Japan's surpassing of Swedish life expectancy in around 1980 and the continuing widening of the gap between the two countries has received special attention (e.g. Svanborg et al., 1985; Wilmoth, 1993) since the Swedish population had been the world's leader in longevity for several preceding decades.
In this chapter, we consider Japan's spectacular improvement in longevity from two perspectives, paying particular attention to the chronic diseases of the elderly population. In the first part of the chapter, we employ a standard demographic approach to analyse the contributions of different age-groups and causes of death to the secular decline in mortality since the mid-1950s. We then use the resulting estimates to explore the plausibility of several hypotheses put forth to explain Japan's post-war mortality improvements. In the second part, we focus on one particular set of explanations, namely dietary factors, by reviewing the evidence from several epidemiological studies relating Japanese diet to health and survival status. Our objective here is to explore the consistency between findings from epidemiological studies of selected