Continuous decline in mortality from coronary heart disease in Japan despite a continuous and marked rise in total cholesterol: Japanese experience after the Seven Countries Study

Abstract

Background : The Seven Countries Study in the 1960s showed very low mortality from coronary heart disease (CHD) in Japan, which was attributed to very low levels of total cholesterol. Studies of migrant Japanese to the USA in the 1970s documented increase in CHD rates, thus CHD mortality in Japan was expected to increase as their lifestyle became Westernized, yet CHD mortality has continued to decline since 1970. This study describes trends in CHD mortality and its risk factors since 1980 in Japan, contrasting those in other selected developed countries.

Methods : We selected Australia, Canada, France, Japan, Spain, Sweden, the UK and the USA. CHD mortality between 1980 and 2007 was obtained from WHO Statistical Information System. National data on traditional risk factors during the same period were obtained from literature and national surveys.

Results : Age-adjusted CHD mortality continuously declined between 1980 and 2007 in all these countries. The decline was accompanied by a constant fall in total cholesterol except Japan where total cholesterol continuously rose. In the birth cohort of individuals currently aged 50–69 years, levels of total cholesterol have been higher in Japan than in the USA, yet CHD mortality in Japan remained the lowest: >67% lower in men and > 75% lower in women compared with the USA. The direction and magnitude of changes in other risk factors were generally similar between Japan and the other countries.

Conclusions : Decline in CHD mortality despite a continuous rise in total cholesterol is unique. The observation may suggest some protective factors unique to Japanese.