426 CELLS, TISSUES, AND ORGANISMS 



severe atherosclerosis is only about one-tenth as much. So Japanese 

 coronaries age much less rapidly. Are the Japanese more fortunate in 

 their genes? Then what about the Japanese men, most with ancestry in 

 the same part of Japan, who die in Hawaii? As a matter of fact, the 

 mortality and hospital data for Japanese in California indicte that they 

 are much more like Minnesota men than like men in Japan. 



Elsewhere (Keys, 1952, 1953, 1955, 1957) I have given evidence 

 which makes it appear that genetic factors do not explain these differ- 

 ences, and that the mode of life, particularly the diet, is largely 

 responsible. 



A central feature in atherosclerosis is the accumulation of lipids, 

 particularly cholesterol, in the intima of the artery. Most, if not all, of 

 tliis cholesterol is derived from the blood, and there is certainly a 

 highly significant relationship between the concentration of cholesterol 

 in the blood plasma and the development of coronary heart disease. 

 Animal experiments demonstrate that atherosclerosis develops when 

 the blood cholesterol is kept at an elevated level for some time. 



But the metabolism of cholesterol differs among species, and the 

 picture of coronary heart disease is peculiar to man. Man is especially 

 susceptible to this kind of aging. The importance of the blood- 

 cholesterol level in man is indicated by many kinds of evidence, in- 

 cluding the results of follow-up studies in which cholesterol is meas- 

 ured in the blood of a large number of men and their eventual ex- 

 perience with coronary heart disease is checked. 



Table III summarizes the findings in the three major follow-up 

 studies reported so far. In the Cooperative Study (see "Technical 

 Group," etc., 1956) the individual men were classed as above or below 

 the median cholesterol value for the whole group; follow-up studies 

 over a period of two to three years after the examination showed that 

 the men in the above-median class had a rate of development of new 

 coronary heart disease 2.6 times that of the below-median class. The 



TABLE III 



Follow-up Studies on Frequency of New Coronary Heart Disease Appearing 

 among Men Classified by Serum-Cholesterol Concentration 



