Fish Tale and Soy Story – Characteristics of the Japanese Diet. Are They Relevant to Dementia?
Epidemiological study of cardiovascular disease contributes to the research in dementia. The first international cardiovascular epidemiological study is the Seven Countries Study in the 1960s which reveals 5 times difference in mortality from coronary heart disease (CHD) – low in Japan and high in the US. Low CHD mortality in Japan was attributed to low total cholesterol (e.g., 160 mg/dl) due to low dietary intake of saturated fat in this population. Because migrant studies of Japanese to the US in the 1970s documented dramatic rise in CHD, it was expected that CHD mortality would rise in Japan when they were exposed to more Westernized lifestyle. During the past 5 decades, dietary intake of saturated fat increased by >100% and total cholesterol increased by 50 mg/dl. Surprisingly, CHD mortality continues to decrease since 1970 and currently is >70% lower compared to the US despite the fact that lifetime exposure to CV risk factors is less favorable in Japanese, indicating some protective factors in this population. To elucidate such factors, we conducted a population-based prospective cohort study of subclinical atherosclerosis and vascular stiffness in men aged 40-49 years at baseline among 300 Japanese, 300 Japanese Americans, and 300 Whites in Pittsburgh (ERA JUMP). We will discuss the findings from this study and potential application of epidemiological study in Japan to dementia research.