Biomedical subjects
Publications and source records attributed to C Sempos.
This report presents descriptive and analytic data for serum total cholesterol, cholesterol lipoproteins, and triglycerides for adults 20-74 years of age by age, sex, and selected subgroups of the population at risk of developing coronary heart disease. This information is from the second National Health and Nutrition Examination Survey, which was conducted during the years 1976-80.
The gradual decline in stroke mortality rates observed in the United States since 1900 accelerated markedly around 1973 for whites and around 1968 for blacks. During the next decade stroke mortality rates decreased by almost 50% so that the United States now experiences one of the lowest stroke mortality rates in the world. Beginning in 1979, however the annual rate of decline in stroke mortality began to slow considerably. Comparing the period 1979-1986 with the previous decade, a 57% slowing in the absolute rate of decline (as estimated by the slope of the linear portion of the mortality curve) was observed for white men; the corresponding slowdowns in the rate of decline were 58% for white women, 44% for black men, and 62% for black women. If the decline during the 1980s had continued at the rate observed for the period 1968/73-1978, there would have been 131,000 fewer stroke deaths during the period 1979-1986, 28,000 fewer in 1986 alone. This slowdown in the rate of decline in stroke mortality is occurring while mortality rates for both coronary heart disease and all causes are leveling off. The reasons for this change in the mortality trend remain unknown, and corresponding trends in the treatment and control of hypertension do not provide an entirely satisfactory explanation.
This report presents descriptive data for serum lipids and lipoproteins by age, sex, and selected socioeconomic variables. This information is from the Hispanic Health and Nutrition Examination Survey, a sample survey of selected groups of civilian noninstitutionalized Hispanic persons residing in selected area of the United States, that was conducted during the period 1982-84.
Using the National Cholesterol Education Program's Guidelines for the Detection, Evaluation, and Treatment of High Blood Cholesterol in Adults and the most recent nationally representative serum total cholesterol and lipoprotein data for adults (ages 20 to 74 years) from the second National Health and Nutrition Examination Survey (1976 to 1980), it is estimated that 41% of adults should have lipoprotein analysis after an initial measurement of serum total cholesterol. Furthermore, it is estimated that 88% of those who need lipoprotein analysis, or 36% of all adults aged 20 to 74 years, are candidates for medical advice and intervention for high blood cholesterol levels. We estimate, based on 1986 population data, that approximately 40 million Americans between the ages of 20 and 59 years are candidates for medical advice and intervention. An additional 24 million Americans aged 60 years and older are candidates. Overall, we estimate that about 60 million Americans aged 20 years and older are candidates for medical advice and intervention for high levels of blood cholesterol, although a less intensive approach might be appropriate for elderly patients.
Since 1976 there has been a leveling off or slowdown in the rate of decline in coronary heart disease (CHD) mortality. The age-adjusted absolute annual rate of decline in CHD mortality rates during 1968-75 (delta rate/100,000 population/year) was virtually identical for White males (-7.54), Black males (-7.85), and Black females (-7.20), and somewhat lower for White females (-4.25). During 1976-85, however, the secular trends diverged considerably. Age-adjusted rates continued to decline at the same annual rate for White males, while the decline was approximately half as steep for the other three race-sex groups. During 1976-85 there was also a leveling off in the average annual per cent change in age-adjusted CHD mortality for Black males and females and White females when compared to 1968-75, while there was no change for White males. As a result, more than 40,000 White and Black females and Black males died of CHD in 1985 than would have died if CHD rates would have continued to decline at the 1968-75 trends. All comparisons were based on a reclassification of cause-of-death codes to maximize comparability between the 8th and 9th Revisions of the International Classification of Disease. These results suggest that the factors which have led to the continued decline in coronary heart disease may not have influenced all the demographic groups in this country equally over the last decade.
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Reports of increased susceptibility of persons from the Indian subcontinent to coronary heart disease led us to examine serum lipids and apolipoproteins in a group of physicians born in India now living in the U.S. A matched sample of U.S.-born physicians working at the same institution was recruited as controls. Fasting triglyceride (TG) levels were twice as high among the Indians (174 vs 86 mg/dl, P = 0.002), total cholesterol modestly increased (193 vs 177 mg/dl, P less than or equal to 0.01) and high density lipoprotein-cholesterol (HDL-C) fraction depressed 36 vs 40 mg/dl, P = 0.006). Both TG and HDL-C were strongly determined by relative obesity in the Americans, but not among the immigrants. Calculated values of low density lipoprotein-cholesterol (LDL-C) were similar in the two groups. Apolipoprotein A-I was significantly lower in a subsample of the Indians, while Apo B was higher. Minor differences between the groups in body mass index, food frequency intake, smoking patterns, alcohol intake and exercise did not significantly influence the results. Hereditary differences in lipid metabolism may have a role in these findings, however, the delayed effects of adaptation to U.S. lifestyle cannot be ruled out.
It has recently been reported that a low intake of calcium may be a risk factor for hypertension. In view of the contradictory results, even when the same survey data base has been used by different researchers, an in-depth analysis was undertaken of the data provided by the two cycles of the National Health and Nutrition Examination Survey (NHANES). Both surveys, conducted in consecutive 4-year intervals during the 1970s, were designed to examine representative samples of the U.S. civilian noninstitutionalized population. The overall descriptive findings in relation to mean blood pressure and calcium intake were virtually identical in the two surveys. Based on "quantile" analysis, neither mean levels of blood pressure nor the prevalence of hypertension was related to calcium intake. Only among black men in NHANES I was a relationship between calcium intake and blood pressure noted. This finding was not apparent among black men in NHANES II or among any of the other sex-race groups in either survey. We conclude that the data of NHANES I and II do not show an association between low calcium intake and blood pressure.
The clinical epidemiology of coronary artery disease (CAD) among black patients has not been well described, particularly in relation to the impact of the major risk factors. Lipoprotein profiles and other risk factors were measured in 114 black patients undergoing cardiac catheterization for probable CAD. Patients (coronary narrowing of 50% or greater; n = 63) were compared to those without significant stenoses (n = 51). Total cholesterol and low-density lipoprotein cholesterol (LDLC) were both significantly associated with the presence of CAD in men and women; however, high-density lipoprotein cholesterol (HDLC) had discriminatory value only for women. The ratio of total cholesterol to HDLC (TC:HDL) separated patients from control subjects in both sexes, most efficiently among women, and was the only lipid variable associated with CAD in the age group over 55 years. Hypertension and angina were frequent in both groups and did not identify those with disease. In summary, LDLC was the best predictor among the lipids for men (likelihood ratio = 9.4) and TC:HDL was the best indicator of disease among women (likelihood ratio = 15.7). Low HDLC levels may, in part, account for the increased incidence of CAD among black women. Further population studies of factors leading to reduced HDLC, namely, obesity and diabetes, are needed.
A total of 417 individuals from all four major sex-race groups were examined for the rate of sodium flux via the countertransport pathway and the sodium concentration within red cells. The age span was from early adolescence to retirement. Males of both races had sizable higher countertransport rates than did women (p less than 0.01), and a slight increase in sodium concentration (p greater than 0.05). Contrariwise, while whites or both sexes had higher countertransport than their black counterparts, sodium concentration was higher in blacks than whites (p less than 0.01). This pattern is not consistent with a direct relationship between both countertransport or sodium concentration and blood pressure which applies across both racial groups. Sex-race differences must be taken into account in any group comparisons of these variables.
A total of 448 individuals ranging in age from 11 to 72 years were studied in a series of seven population-based surveys. Although the relationship was positive in all surveys, a significant correlation was noted between sodium-lithium countertransport and blood pressure in only three of the seven. Hypertensives as a group had significantly higher levels of countertransport than did those with a normal blood pressure. In stepwise regression analysis, however, entering weight into the equation eliminated a significant predictive effect of countertransport. Red cell sodium concentration and membrane leak did not bear any significant relationship to blood pressure. The association between countertransport and blood pressure appears to be weaker in the general population than previously reported for case-control studies.
All-causes mortality rates turned sharply upward for Polish men around 1972. Increases of 25 percent or greater were recorded for all five-year age groups between 40 and 59 years. Other indices, including infant mortality and death rates for women, either continued to improve or did not change. The primary causes accounting for this upturn appear to be cardiovascular diseases and cancer of the lung. The epidemiological pattern in Poland reflects in part the long-term trend for consumption of food, alcohol, and tobacco to approximate that found in Western industrialized countries. The role of more generalized social changes associated with Poland's rapid industrialization cannot be evaluated directly. Although it is still too early to see the effect of the social crisis of the last two years, economic disruption and shortages are not the main factors accounting for the upturn in Polish mortality through 1980. In fact, the success of the Polish economic strategy appears to be the underlying social cause.
In a series of population-based studies, the relationship between a family history of hypertension and sodium transport was examined. In the total sample of 417 individuals, and in each sex-race-specific sub-sample, no significant differences were noted in red cell sodium-lithium countertransport, sodium concentration, or passive leak. A higher proportion of hypertensives was not found in the group with a positive family history, and blood pressures were only slightly higher in those--compared to those without--a positive family history. If family history of hypertension is associated with levels of countertransport, it would appear that the relationship is weak in the general population.
A randomized crossover trial on the effect of salt restriction on blood pressure was carried out involving 124 adolescents (mean age 16 years). Dietary sodium was reduced from approximately 110 to 45 mEq/24 h for a period of 24 days. Blood pressure was non-significantly lower at the end of the experimental diet for all participants. A slight (0.7 kg), yet statistically significant fall in weight was observed (P less than 0.05). Subgroup analysis demonstrated that participants whose body mass index was below the median had a statistically significant fall in systolic blood pressure (P less than 0.05); fall in weight and increase in heart rate were also more pronounced in the less obese individuals. It would appear that moderate sodium reduction does not have an overall short-term effect on blood pressure in normotensive adolescents. However, body size as reflected in body mass index may influence blood pressure response to sodium reduction.
Adult male mortality has turned sharply upward in Eastern Europe and the Soviet Union. Excluding the German Democratic Republic, for which data are not available, agestandardized death rates for men aged 40 to 69 years increased an average of 12 percent from the early 1960s to the mid-1970s. These secular trends were associated with consistent economic growth. At least for adult men, this period of social development has led to a marked deterioration in health.
High school students who had at least one parent with hypertension (n = 22) were compared to schoolmates of the same age with a negative family history of hypertension in the parents (n = 21). We investigated in both groups the maximal rate of the ouabain-sensitive Na pump and the Na-K cotransport in nystatin-loaded cells and the Lii-Nao countertransport in lithium-loaded cells. The two groups were significantly different only in the sum of net Na transport mediated by the Na-K pump and Na-K cotransport. The mean diastolic blood pressure in the positive family history group was significantly higher. With control for blood pressure the difference in the maximal rate of Na transport was no longer significant; it remains uncertain if control for blood pressure represents "over-adjustment'. The finding of a higher maximal rate of Na transport in these adolescents who are at increased risk of future hypertension, yet currently well within the normal range, suggests that abnormal sodium metabolism may be a useful marker and appears early in the pathogenesis of this disease.
Differences in red cell sodium content and sodium-lithium countertransport were studied in black and white children with a mean age of 12 years. For both boys and girls red cell sodium content was higher in blacks and countertransport lower (P less than 0.05). For both ethnic groups red cell sodium was lower in girls than boys and a consistent positive relationship was noted between body mass index and countertransport. Despite the lower red cell Na-Li countertransport values in black compared to white children, a significant positive correlation with systolic blood pressure was found independent of adiposity. In contrast, no correlation was evident between Na-Li countertransport and blood pressure in the white children. If red cell cation transport is confirmed as a marker for hypertension, study of racial differences may help explain the twofold higher prevalence of this disease among blacks.