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DENSITOMETRIC ANALYSIS OF BODY COMPOSITION: REVISION OF SOME QUANTITATIVE ASSUMPTIONS*

One can trace to Archimedes the idea that in a system consisting of two additive components which are mixed but the densities of which are known ( d l , d 2 ) , the determination of the density of the system ( D ) allows one to calculate the proportional masses of the two components. Let’s denote these components as W1 and W2.S Then, in a system with total weight W = W1 + Wz, the general equation for calculating component W1 expressed as a fraction (w1) of the total body weight is:

The Electrocardiogram in Population Studies A Classification System

Information now available about the prevalence and incidence of coronary heart disease is seriously deficient because of the lack of standardized and objective methods of collection, tabulation, interpretation, and reporting of survey data. Chief reliance in the objective diagnosis of coronary heart disease rests on the electrocardiogram, a crucial tool in population studies. A classification system for the electrocardiogram in epidemiologic studies has been developed, tested, and herein presented. It is adapted to the usual clinical reading technics of the electrocardiographer. It embodies criteria widely employed and of diagnostic and prognostic import, but no stipulations about interpretation are made. The system permits more valid comparisons of data on heart disease between populations. It is susceptible to modern methods of data processing.

Serum cholesterol response to changes in the diet: IV. Particular saturated fatty acids in the diet.

For many dietary changes satisfactory prediction of the average change in the serum cholesterol level of man in mg./100 ml., is given by Δ Chol. = 1.35(2ΔS − ΔP) + 1.5ΔZ where S and P are percentages of total calories provided by glycerides of saturated and polyunsaturated fatty acids in the diet and Z2 = mg. of dietary cholesterol/1000 Cal. This formula fails, however, when the dietary change involves large amounts of cocoa butter and discrepancies also appear with beef tallow or hydrogenated coconut oil diets. Controlled dietary experiments at the University of Minnesota and at 2 other centers, provide 63 sets of comparisons of serum cholesterol averages for groups of men on each of 2 chemically characterized diets. Least-squares analysis indicates that stearic acid, as well as saturated fatty acids containing fewer than 12 carbon atoms, have little or no effect on serum cholesterol in man. The equation, Δ Chol. = 1.2(2ΔS′ − ΔP) + 1.5ΔZ, yields good correlation (r = 0.93) with the observed values in these 63 sets of data. This formulation also resolves heretofore puzzling discrepancies in the literature.

Serum cholesterol response to changes in the diet: II. The effect of cholesterol in the diet.

The series of metabolic ward experiments, with 22 physically healthy men in each, covered dietary cholesterol intakes from 50 to 1450 mg. daily, with all other variables controlled. The serum-cholesterol data, plus the data from comparable experiments reported from 4 other institutions, were analyzed in regard to average serum cholesterol response (Δ Chol., mg./100 ml.) to changed cholesterol intake. Least-squares solution, using serum cholesterol responses in 19 sets of dietary cholesterol comparisons, gives Δ Chol. = 1.5(Z2 − Z1), where the subscripts refer to the diets compared and Z is the square-root of the dietary cholesterol, measured as mg./1000 Cal. The correlation between the average Δ Chol. predicted and that observed is r = 0.95. The serum response was the same over a wide range of dietary fat composition. Ordinary American diets range from about about 150 to 350 mg. cholesterol/1000 Cal. These extremes correspond to an average difference of about 9 mg. of cholesterol/100 ml. of serum if all other variables are constant. Change from 250 mg./l000 Cal. to a cholesterol-free diet will cause an average fall of about 24 mg./100 ml. of serum. But a 50 per cent decrease in dietary cholesterol will produce an average decrease in the serum of only about 7 mg./100 ml. For the purpose of controlling the serum level, dietary cholesterol should not be completely ignored but attention to this factor alone accomplishes little.

The Seven Countries Study : 2,289 deaths in 15 years

Among 11,579 men ages 40-59 without evidence of cardiovascular disease, 2,289 died in 15 years, 618 from coronary heart disease. The 15 cohorts in seven countries (four regions) differed in all-causes death rate, mainly reflecting great differences in coronary mortality. Among characteristics of entry, only mean blood pressure helped to explain cohort differences in all-causes death rate. Three-quarters of the variance in coronary death rate was accounted for by differences in mean serum cholesterol and blood pressure of the cohorts. The mortality risk for individuals was examined in each of the regions. For coronary death, age, serum cholesterol, blood pressure, and smoking were highly significant in all regions except Japan, where coronary deaths were too few for evaluation. Relative weight was not significant anywhere. Physical activity was significant only in southern Europe, where differences are associated with socioeconomic status. For all-causes death, age and blood pressure were highly significant risk factors in all regions as was smoking habit, except in Japan. Relative body weight tended to be a negative risk factor everywhere, significantly so in southern Europe. Expectations for coronary death from the experience in the United States and northern Europe greatly exceeded observed deaths in southern Europe for men of their age, serum cholesterol, blood pressure, smoking habits, physical activity, and relative weight. The reverse, prediction of coronary deaths in America and in northern Europe from the southern European experience, greatly underestimated the deaths observed. Similar cross-predictions between the United States and northern Europe were good for all-causes deaths, excellent for coronary deaths. Analysis of time trends in relationships of mortality to entry characteristics showed continued importance of age, blood pressure, and smoking and a tendency for the importance of cholesterol to fall in the last 5 years of follow-up.

Serum cholesterol response to changes in the diet: I. Iodine value of dietary fat versus 2S-P.

In men in calorie equilibrium, changes in dietary fat produce responses in the serum cholesterol level that, on the average, are predictable from the percentages of total calories provided by saturated (S) and polyunsaturated (P) fatty acid glycerides in the diets concerned. S and P have opposing actions and, in general, Δ Cholesterol (mg./100 ml.) = 2.7ΔS − 1.3ΔP, where Δ refers to the difference between 2 diets. Increasing the number of double bonds beyond 2 in polyunsaturated fatty acids does not result in proportionate increases in serum cholesterol-lowering effect. The mono-enes oleic and erucic acid have little or no effect on the serum cholesterol level when they are exchanged in the diet for equal calories of simple carbohydrate. Changes of fats in the diet produce serum cholesterol responses that are also correlated with the iodine values, or the square-roots of those values, of the fats concerned when the iodine value happens to be highly correlated with 2.7S - 1.3P. When changes in diet fats involve substantial differences in amounts of mono-enes, or of fatty acids containing more than 2 double bonds, the serum cholesterol response has a low or negligible correlation with the iodine value, or its square-root, of the fats.

Basal metabolism and age of adult man

Abstract Basal metabolism measurements made on young men were repeated after 19 yr. Basal metabolism was repeatedly measured over a period of 22 yr on men initially aged 44–56 yr. In the younger men the basal metabolic rate per individual man decreased by an average of only 3% in 19 yr but during this period these men had an average gain of 10.6 kg so there was a decrease of 9% in the average metabolic rate per unit of body weight. In the older men, average weight gain over 22 yr was only 1 kg, and there was not any significant decrease in individual oxygen consumption with age. The commonly cited figures on age changes in basal metabolism in adults, derived from cross-sectional surveys, much overestimate the true age effect.

Probability of Middle-Aged Men Developing Coronary Heart Disease in Five Years

Characteristics of 11,132 men aged 40-59 years and free from coronary heart disease (CHD) at entry were related to follow-up experience, using multivariate analysis. In 5 years among 2,404 U. S. railroad men and 8,728 European men there were 615 cases of CHD, 214 of whom died from CHD or suffered definite nonfatal infarction.With five entry characteristics (age, systolic blood pressure, serum cholesterol, smoking habit, and body mass index), multiple logistic solutions for Europeans and Americans, separately, gave estimates of the individual probability of CHD. Classified by deciled scores for these probabilities, the expected and observed CHD cases were highly correlated (r = 0.930-0.981). Predictions based on European data applied to Americans, and vice versa, gave similar high correlations but American incidence was excessive compared with European experience.Application of the analysis coefficients obtained from data in Europe and in the U. S. railroad to 6,221 other U. S. men 40-59 years of age, CHD-free at entry, gave good prediction of relative risk (r = 0.94) for observed versus predicted cases in deciles of risk score; however, the actual numbers of cases were underpredicted.From single measurements of a few characteristics the multiple logistic solution usefully estimates the relative risk of CHD for individuals. Age, systolic pressure, and serum cholesterol are universally powerful predictors of risk. Variables not measured in this study or not yet identified contribute to the risk of CHD among American men.

Coronary Heart Disease among Minnesota Business and Professional Men Followed Fifteen Years

Relative weight, body fatness (skinfold thickness), blood pressure, and serum cholesterol are reported from 281 Minnesota business and professional men, initially clinically healthy and aged 45 to 55, who were followed by annual examinations since the winter of 1947–48. In 15 elapsed years, coronary heart disease developed definitely in 32 men and possibly in 16 other men.The incidence of coronary heart disease tended to be higher among men above the median at first examination in relative weight, body fatness, systolic and diastolic blood pressure, and serum cholesterol concentration but these segregations were not statistically significant except with serum cholesterol, which was associated with p < 0.001. The data for the last pre-disease year on the men who developed coronary heart disease showed a significant relationship between incidence and systolic blood pressure as well as for cholesterol. Average data over all pre-disease years showed significantly reduced risk among the men in the bottom quartile for diastolic as well as for systolic blood pressure, while the cholesterol level was significantly prognostic over the entire range of that variable. The few men who developed coronary heart disease with low cholesterol values tended to be in the top 20 per cent of the distribution of blood pressure or relative weight or both.Relative weight showed a high but still imperfect correlation with body fatness. Arterial blood pressure tended to be elevated in extremely obese or grossly overweight men. Serum cholesterol was not significantly related to any of the other variables.Men who developed coronary heart disease tended to have low values for cholesterol in the alpha-lipoprotein fraction in the serum but the ratio of cholesterol in the alpha- to the beta-lipoprotein fraction of the serum was no more prognostic than total cholesterol alone.Comparison with similar follow-up data from Framingham, Massachusetts, Albany, New York, and Chicago, show a high degree of concordance. In all series relative weight had least significance and the incidence of coronary heart disease rose continuously with the serum cholesterol level. With men classifiedaccording to pre-disease cholesterol level, about 80 per cent of the total variance in relative subsequent risk is accounted for by regression of risk on the cholesterol value raised to any power from 2 to 3 and the correlation between observed and predicted relative risk is of the order of r = 0.9.

Coronary heart disease: overweight and obesity as risk factors.

Abstract The relationship of relative weight and of skinfold thickness to the 5-year incidence (632 cases) of coronary heart disease was examined in men aged 40 through 59 years at entry to the stu...