 Link
to: Academic Health Center : School
of Public Health : U of M Home |
 |
One Stop | MyU
| Search U of M  |
 |
|
|
|
 |
|
 Overview: The Seven Countries Study in Brief By Henry Blackburn, MD Collaborators Selected References Ancel Keys at Minnesota, and his colleagues in seven countries, posed the hypothesis that differences among populations in the frequency of heart attacks and stroke would occur in some orderly relation to physical characteristics and lifestyle, particularly composition of the diet, and especially fats in the diet. To test this idea we carried out surveys from 1958 to 1970 in populations of men ages 40-59, in eighteen areas of seven countries, with follow-up for deaths in the cohorts up to the present day. The formal surveys were undertaken after successful pilot experiences in Finland, Italy, and Greece in 1956 and 1957. Most of the areas were stable and rural and had wide contrasts in habitual diet. In those days, we did not consider involving women because of the great rarity of cardiac events among them, and the invasiveness of our field examinations. The Seven Countries Study is the prototypical comparison study of populations, made across a wide range of diet, risk, and disease experience. It was the first to explore associations among diet, risk, and disease in contrasting populations (ecologic correlations). Central chemical analysis of foods consumed among randomly selected families in each area, plus diet-recall measures in all the men, allowed an effective test of the dietary hypothesis. The study was unique for its time, in standardization of measurements of diet, risk factors, and disease; training its survey teams; and central, blindfold coding and analysis of data. There were, of course, limitations: the relatively small number of units for ecological correlations; the selection of the samples in the different geographic areas in part for reasons of convenience; and the technical challenges of conducting surveys across cultures by national teams, often working under difficult field conditions. The core of investigators was recruited by Ancel Keys and the study coordinated from the Laboratory of Physiological Hygiene, located in offices under Memorial Stadium, Gate 27, at the University of Minnesota. I served as Project Officer in the early years, while Henry Taylor directed the Railroad Study, the U.S. component of the Seven Countries Study. A few years into the study, central coordination of data was shifted to Alessandro Menotti at the University of Rome. All field studies were carried out under the aegis of a National Heart Institute grant. Local support was always substantial, however, in that the central grant only averaged about $25,000 a year per collaborating center. Both public and private sources, as well as the World Health Organization, provided direct and logistic support. The study has been criticized for the method in which populations were selected for the study, and the way that the population (ecologic) correlations, with limited numbers of units, were carried out. These days, the configuration of populations for such internal and international comparisons is strengthened by the random selection of greater numbers of units. But the Seven Countries Study was state-of-the-art for its time, and the concept ahead of its time. Ecologic correlations are relatively weak in arriving at causal inference about disease. However, they are crucial indicators of population causes of disease, and of public health preventive strategies, where the epidemiologic evidence is congruent with that from the laboratory and the clinic. The Seven Countries Study, more than any other cardiovascular disease study, has directed attention to the causes of population rates of disease, while confirming the importance of an individual's risk within populations. It documented major differences in the mass phenomena related to differences in disease rates, and it demonstrated the degree to which composition of the diet -- particularly levels of saturated fatty acids and mean serum cholesterol levels -- predict present and future population rates of coronary heart disease. The predictive equations derived from the population correlations provide the general rule, while departure from prediction points up important exceptions, such as the excess of coronary heart disease in East Finland and its rarity in Crete. These exceptions, in turn, have provided impetus to further research into causal factors other than dietary saturated fatty acids and cholesterol.
|
|
|||||||||||||||||||||||||||||||||||
