Seven Countries Study
Study Category: The Cohort Studies (1947-1972)
Year Begun: 1957
Location: U.S., Italy, Greece, Yugoslavia, the Netherlands, Finland, and Japan
Principal Investigator: Keys, Ancel
The Seven Countries Study was first to examine systematically the relation among diet, lifestyle, risk factors and rates of coronary heart disease and stroke in populations contrasting in diet, especially dietary fat. The idea arose in the minds of investigators who integrated clinical, laboratory, and early population evidence into questions about the cultural origins and possible prevention of mass cardiovascular diseases (CVD).
Ancel Keys gave the study its scope, design, and direction and coordinated the program from Minnesota, with field surveys beginning in 1957 in the U.S., Italy, Greece, Yugoslavia, the Netherlands, Finland, and Japan. Repeat surveys for characteristics and morbidity were made at 5 and 10- year anniversaries and follow-up of mortality is complete for 45 years, with excellent response rates throughout. Standardized methods were developed for measurements and diagnoses; teams were centrally trained, and data were blinded and centrally analyzed. The populations were predominantly rural and engaged in traditional agricultural (or fishing, logging) pursuits. Due to the rarity worldwide of CVD among women in the 1950s, the study was confined to men ages 40-59. The study has been extended to include elderly cohorts in Finland, the Netherlands, and Italy, and enhanced by new dietary surveys and analyses. Multivariate analyses of single and combined measurements are now mainly by Cox hazard ratio analysis.
The Seven Countries Study provided evidence confirming the original hypotheses, that elevated mean blood cholesterol levels and intake of saturated fatty acids is a major and apparently necessary factor in the population burden of atherosclerotic diseases. Populations with saturated acid intake less than 10 percent of daily energy have little coronary heart disease or thrombotic stroke despite widely varying total fat intake or usual levels of blood pressure or high rates of tobacco use. Multivariate analysis of population rates and risk factors reveal that diet and smoking “explain” most of the differences in population rates and that the “standard” CVD risk factors operate universally within populations.
The main implications of the Seven Countries Study are that the mass burden and epidemic of atherosclerotic diseases has cultural origins, is preventable, can change rapidly, and is strongly influenced by the fatty composition of the habitual diet. The study implies the universal susceptibility of humans to CVD but that the frequency of susceptible phenotypes is greatly reduced in favorable environments. It suggests there may be other and important protective elements in the diet and lifestyles of Crete and Japan. (HB)
More On The Study
The essential study findings may be found in two monographs:
Keys, Ancel, C. Aravanis, H. Blackburn, R. Buzina, B.S Djordjevic, A.S. Dontas, F. Fidanza, M.J. Karvonen, N. Kimura, A. Menotti , I. Mohacek , S. Nedeljkovic, V. Puddu, S. Punsar, H.L. Taylor, F.S.P. Van Buchem. 1980. Seven countries. A multivariate analysis of death and coronary heart disease. Cambridge: Harvard University Press.
Kromhout, Daan, Alessandro Menotti, Henry Blackburn, eds. 2002. Prevention of coronary heart disease. Diet, lifestyle and risk factors in the Seven Countries Study. Norwell: Kluwer Academic Publishers.
To view documents associated with the Seven Countries Study, see the following links:
Website: The Seven Countries Study
Prevalence of Coronary Heart Disease: A Memorandum from Ancel Keys, 4 March 1957- click here
To view a current bibliograpy of joint publications of the Seven Countries Studies (as of November 2011, A. Menotti version) click here.
Please also visit the website, On the Trail of Heart Attacks in Seven Countries, which includes an essay by Henry Blackburn “On the Trail of Heart Attacks in Seven Countries,” a dedication to Ancel Keys and a foreword.