Alan Dyer

Blood pressure, stroke, and coronary heart disease. Part 1, Prolonged differences in blood pressure: prospective observational studies corrected for the regression dilution bias.

The associations of diastolic blood pressure (DBP) with stroke and with coronary heart disease (CHD) were investigated in nine major prospective observational studies: total 420,000 individuals, 843 strokes, and 4856 CHD events, 6-25 (mean 10) years of follow-up. The combined results demonstrate positive, continuous, and apparently independent associations, with no significant heterogeneity of effect among different studies. Within the range of DBP studied (about 70-110 mm Hg), there was no evidence of any threshold below which lower levels of DBP were not associated with lower risks of stroke and of CHD. Previous analyses have described the uncorrected associations of DBP measured just at baseline with subsequent disease rates. But, because of the diluting effects of random fluctuations in DBP, these substantially underestimate the true associations of the usual DBP (ie, an individuals long-term average DBP) with disease. After correction for this regression dilution bias, prolonged differences in usual DBP of 5, 7.5, and 10 mm Hg were respectively associated with at least 34%, 46%, and 56% less stroke and at least 21%, 29%, and 37% less CHD. These associations are about 60% greater than in previous uncorrected analyses. (This regression dilution bias is quite general, so analogous corrections to the relations of cholesterol to CHD or of various other risk factors to CHD or to other diseases would likewise increase their estimated strengths.) The DBP results suggest that for the large majority of individuals, whether conventionally hypertensive or normotensive, a lower blood pressure should eventually confer a lower risk of vascular disease.

INTERSALT study findings. Public health and medical care implications.

INTERSALT found a significant association between 24-hour urine sodium excretion and systolic blood pressure in individuals. There was also a significant association between sodium and slope (increase) of blood pressure with age across population samples. The weight of evidence from animal-experimental, clinical, intervention, and epidemiological data favors a causal relation. INTERSALT data from 52 centers in 32 countries permit an estimate of effect on average population blood pressure of lower sodium intake. Based on the sodium-blood pressure association in individuals, it was estimated that a habitual population sodium intake that was lower by 100 mmol/day (e.g., 70 vs. 170 mmol/day) would correspond to an average population systolic pressure that was lower by at least 2.2 mm Hg. This size difference in systolic blood pressure in major US and UK population studies is associated with 4% lower risk of coronary death and 6% lower risk of stroke death in middle age. If habitual diet is both lower in sodium and higher in potassium with lower alcohol intake and less obesity, INTERSALT data estimate average population systolic pressure would be lower by 5 mm Hg. This was calculated to correspond to a 9% lower risk of coronary death and a 14% lower risk of stroke death. INTERSALT cross-population data also suggest that, with a 100 mmol/day lower sodium intake over the life span, the average increase in population systolic pressure from age 25 to 55 years would be less by 9 mm Hg, corresponding at age 55 to a 16% lower risk of subsequent coronary death and 23% lower risk of stroke death. These findings have importance in long-term population strategy for reduction of cardiovascular mortality.

Nutritional Therapy for High Blood Pressure: Final Report of a Four-Year Randomized Controlled Trial— The Hypertension Control Program

A four-year trial assessed whether less severe hypertensives could discontinue antihypertensive drug therapy, using nutritional means to control blood pressure. Randomization was to three groups: group 1--discontinue drug therapy and reduce overweight, excess salt, and alcohol; group 2--discontinue drug therapy, with no nutritional program; or group 3--continue drug therapy, with no nutritional program. In groups 1 and 2 patients resumed drug therapy if pressure rose to hypertensive levels. Loss of at least 4.5 kg (10 + lb) was maintained by 30% of group 1, with a group mean loss of 1.8 kg (4 lb); sodium intake fell 36% and modest alcohol intake reduction was reported. At four years, 39% in group 1 remained normotensive without drug therapy, compared with 5% in group 2. Study findings demonstrated that nutritional therapy may substitute for drugs in a sizable proportion of hypertensives or, if drugs are still needed, can lessen some unwanted biochemical effects of drug treatment.

Blood pressure in four remote populations in the INTERSALT Study.

Four remote population samples (Yanomamo and Xingu Indians of Brazil and rural populations in Kenya and Papua New Guinea) had the lowest average blood pressures among all 52 populations studied in INTERSALT, an international cooperative investigation of electrolytes and blood pressure. Average systolic blood pressure was 103 versus 120 mm Hg in the remaining INTERSALT centers; diastolic blood pressure in these four population samples averaged 63 versus 74 mm Hg in the 48 other centers. There was little or no upward slope of blood pressure with age; hypertension was present in only 5% of the rural Kenyan sample and virtually absent in the other three centers. Also in marked contrast with the rest of the centers was level of daily salt intake, as estimated by 24-hour urinary sodium excretion. Median salt intake ranged from under 1 g to 3 g daily versus more than 9 g in the rest of INTERSALT populations. Average body weight was also low in these four centers, with no or low average alcohol intake, again unlike the other centers. The association within these four centers between the above variables and blood pressure was low, possibly reflecting their limited variability. While several other INTERSALT centers also had low average body weight or low prevalence of alcohol drinking, when this was accompanied by much higher salt intake (7–12 g salt or 120–210 mmol sodium daily), hypertension prevalence ranged from 8% to 19%. These findings confirm previous reports that in populations with a low salt intake, there is little or no hypertension or rise of blood pressure with age. While the contributory role of other characteristics of these populations must also be considered, the results are consistent with the view that a certain minimum salt intake is essential for rise in blood pressure with age in adults and a high frequency of hypertension in populations.

Serum uric acid and 11.5-year mortality of middle-aged women: Findings of the Chicago heart association detection project in industry

The relationships of serum uric acid to mortality from all causes, the cardiovascular diseases, and cancer were evaluated in 6797 white women age 35-64 years followed for an average of 11.5 years in the Chicago Heart Association Detection Project in Industry (CHA). Serum uric acid levels at baseline were strongly and significantly associated with all causes mortality in this cohort, with control for multiple risk factors and with exclusion of hypertensives on treatment. When the analysis was performed on age-specific groups 35-44, 45-54, and 55-64 years of age, the association was observed primarily in women in the oldest age group. All cardiovascular deaths, deaths due to coronary heart disease, and all cancer deaths were also associated with serum uric acid levels in the 55-64 year old group. The relationships persisted with control for multiple risk factors and with exclusion of treated hypertensives. A site-specific analysis of cancer deaths demonstrated elevations in mean serum uric acid levels for nearly all sites. Differences in mean serum uric acid levels between decedents and survivors tended to be largest in the first 5 years of follow-up for the cardiovascular deaths, but for cancer decedents they tended to be larger for subsequent years of follow-up. As an initial report on the association of serum uric acid and cancer in women in this age group, the results of this study require confirmation. Although hormonal influences may play a role, pathophysiologic mechanisms relating serum uric acid to mortality in white women aged 55-64 are currently unknown.

Alcohol intake and blood pressure in young adults: The CARDIA study

Associations between self-reported average daily alcohol intake and blood pressure were assessed in 5031 black and white men and women ages 18-30 from the Coronary Artery Risk Development in Young Adults Study (CARDIA). In general, intake was positively but weakly related to both systolic and diastolic blood pressure. Associations with systolic pressure were generally stronger than those with diastolic pressure. With average daily alcohol intake categorized as none, 0.1-9.9 ml, 10.0-19.9 ml, 20.0-29.9 ml, and 30.0+ ml, mean systolic pressure, adjusted for age, body mass index, education, smoking, and physical activity, increased progressively with increasing intake in black and white men and in white women. Mean diastolic pressure increased progressively with increasing intake only in white men and women, but was highest for those averaging 30.0+ ml per day in black women as well as white men and women. Mean pressures were also compared for those averaging 75.0+ ml per day (men) or 50.0+ ml per day (women) vs those reporting no intake. Differences in adjusted mean pressures for white men were 3.2 mmHg (95% confidence limits (CL) -0.3, 6.8) for systolic pressure and 1.7 mmHg (-1.6, 5.0) for diastolic pressure. In black men differences were 4.4 mmHg (1.4, 7.4) and 3.4 mmHg (0.6, 6.3), respectively. Differences in white women were 1.4 mmHg (-2.5, 5.3) for systolic pressure and 0.9 mmHg (-2.7, 4.5) for diastolic pressure and for black women, -0.2 mmHg (-4.3, 3.8) and 1.9 mmHg (-1.9, 5.8). Separate analyses in smokers and nonsmokers of the associations between alcohol intake and blood pressure suggested that associations may differ by smoking status in some sex-race groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Neuroticism and cynicism and risk of death in middle-aged men: The Western Electric study

&NA; MMPI measures of neuroticism (N) and of cynicism (C) were obtained at the initial examination of 1871 employed, middle‐aged men in Chicago. Neither N nor C was significantly associated cross‐sectionally with systolic blood pressure or serum cholesterol, but both were positively associated with cigarette smoking and alcohol consumption. N was not significantly associated with risk of death from coronary disease, other cardiovascular diseases, cancer, all other causes combined, or all causes combined after adjustment for C, age, cigarette smoking, alcohol consumption, systolic blood pressure, and serum cholesterol. C was significantly associated with coronary death and total mortality after adjustment for N and the other variables listed above, and relative risks of 1.4 to 1.6 were observed for all endpoints. These results support the idea that neuroticism is not associated with major causes of mortality, but that cynicism is associated with several causes. The associations between cynicism and mortality may be mediated by cigarette smoking and excessive alcohol consumption since adjustment for these factors may have been incomplete due to correlation between cynicism and errors in self‐reported data.

Ethnic differences in blood pressure, pulse rate, and related characteristics in young adults. The CARDIA study.

This study examined ethnic differences in blood pressure and pulse rate in young adults to see whether the differences, if they exist, can be explained by differences in body mass index, lifestyle, psychological, and socioeconomic characteristics. Data used were from the baseline examination of the Coronary Artery Risk Development in (Young) Adults Study (CARDIA). CARDIA is a longitudinal study of lifestyle and evolution of cardiovascular disease risk factors in 5,116 young adults, black and white, men and women, aged 18-30 years, of varying socioeconomic status. Young black adults had higher mean systolic blood pressure and slightly higher mean diastolic blood pressure than young white adults. For both men and women, the blood pressure differences between blacks and whites tended to be greater for the age group 25-30 than for the age group 18-24 years. Among the variables studied, body mass index, duration of exercise on the treadmill, number of cigarettes smoked per day, and number of alcoholic drinks per week were consistently associated with blood pressure. The blood pressure differences were greatly reduced after adjusting for these variables. Black participants had lower mean pulse rate than white participants. The differences tended to be greater for the age group 18-24 than for the age group 25-30 years. Among the variables studied, only duration on treadmill and number of cigarettes smoked per day were consistently correlated with pulse rate. With adjustment for duration on treadmill, the differences in pulse rate increased. These results suggest that differences in ethnic pattern of blood pressures and pulse rate with age may be due in part to obesity, physical fitness, alcohol consumption, and cigarette smoking.

Sex differential in the relationship of electrocardiographic ST-T abnormalities to risk of coronary death: 11.5 year follow-up findings of the Chicago Heart Association Detection Project in Industry.

The independent contributions of ST segment depression and/or T wave abnormality (ST-T abnormalities) on the baseline resting electrocardiogram to risk of 11.5 year coronary heart disease (CHD) mortality were explored among 9203 white men and 7818 white women who were 40 to 64 years old and without definite CHD at entry in the Chicago Heart Association Detection Project in Industry. At baseline, prevalence rates of ST-T abnormalities were age related for both sexes, and at every age the rate was higher in women than men (age-adjusted prevalence rates 12.3% and 8.1%, respectively). Univariate analysis showed that ST-T abnormalities were associated with significantly increased risk of death from CHD for both men and women. However, men with ST-T abnormalities had much greater age-adjusted and multiple risk factor-adjusted absolute excess risk and relative risk than women with such electrocardiographic abnormalities. When baseline age, diastolic pressure, serum cholesterol, cigarettes/day, history of diabetes, and baseline use of antihypertensive medication were included in the multivariate analysis, ST-T abnormalities remained significantly related to death from CHD in men but not women. The interaction term between sex and ST-T abnormalities was at a borderline level of statistical significance by Cox regression analysis. In conclusion, ST-T abnormalities indicate an increased risk of subsequent death from CHD independent of major coronary risk factors for middle-aged U.S. men, but this is not clearly so for women.

Major and minor electrocardiographic abnormalities and risk of death from coronary heart disease, cardiovascular diseases and all causes in men and women.

The independent contributions of baseline major and minor electrocardiographic (ECG) abnormalities to subsequent 11.5 year risk of death from coronary heart disease, all cardiovascular diseases and all causes were explored among 9,643 white men and 7,990 white women aged 40 to 64 years without definite prior coronary heart disease in the Chicago Heart Association Detection Project in Industry. At baseline, prevalence rates of major ECG abnormalities were higher in women than in men, with age-adjusted rates of 12.9 and 9.6% (p less than 0.01), respectively. Minor ECG abnormalities were more common in men than in women (7.3 versus 4.5%, p less than 0.01). Both major and minor ECG abnormalities were associated with an increased risk of death from coronary heart disease, all cardiovascular diseases and all causes. The strength of these associations was greater in men than in women. When baseline age, diastolic pressure, serum cholesterol, cigarettes smoked per day, diabetes and use of antihypertensive medication were taken into account, major abnormalities continued to be significantly related to each cause of death in both genders with much larger adjusted absolute excess risk and relative risk for men than for women. In multivariate analyses, minor ECG abnormalities contributed independently to risk of death in men, but not clearly so in women. The results indicate the independent association between ECG abnormalities and mortality from coronary heart disease, all cardiovascular diseases and all causes, with greater relative significance in middle-aged United States men than women.