BLOOD PRESSURE AND HYPERTENSIVE DISEASE AMONG NEGROES AND WHITES; A STUDY IN EVANS COUNTY, GEORGIA

Rates of abnormal aldosterone/renin ratio in African-origin compared to European-origin patients: A retrospective study

INTRODUCTION

The aldosterone/renin ratio is the initial screening test for primary hyperaldosteronism (PHA), but little data exists regarding ethnic variations in this.

METHODS

Following clinical observation of a high prevalence of abnormal aldosterone/renin ratio (ARR) in patients of African-origin, we retrospectively reviewed all ARR measurements in a single centre over 10 years. Rates of hypokalaemia, intraventricular septal thickness (IVS, by echocardiography) and adrenal imaging were recorded when available.

RESULTS

Aldosterone/renin ratio was available in 1473 patients, and abnormal in 374 (25.4%). Abnormal ARR was observed in 305/1349 (22.6%) of European-origin and 69/124 (55.6%) of African-origin patients (P < 0.001). Among those with abnormal ARR, hypokalaemia (<3.5 mmol/L) was documented on at least one occasion in 171/305 (56.1%) European-origin and 43/69 (62.3%) African-origin patients (P = 0.35). Median (range) IVS was 1.57 (0.78-2.80) cm in African-origin and 1.20 (0.69-2.18) cm in European-origin patients (P < 0.002); IVS did not correlate with aldosterone or ARR however. Adrenal adenoma was identified in 41/170 (24.1%) of European-origin and 4/29 (13.7%) African-origin patients (P = 0.15), while hyperplasia was identified in 35/170 (20.5%) of European and 8/29 (27.5%) African patients (P = 0.39).

CONCLUSION

In summary, ARR was abnormal in 55.6% of African-origin patients screened at an Irish hospital. Rates of hypokalaemia were similar between European-origin and African-origin patients. These findings have implications for the use of current screening guidelines for ARR in African-origin patients and also for the mechanistic role of aldosterone in hypertensive complications in African-origin patients.

Cortical cerebral blood flow in ageing: effects of haematocrit, sex, ethnicity and diabetes

OBJECTIVES

Cerebral blood flow (CBF) estimates from arterial spin labelling (ASL) show unexplained variability in older populations. We studied the impact of variation of haematocrit (Hct) on CBF estimates in a tri-ethnic elderly population.

MATERIALS AND METHODS

Approval for the study was obtained from the Fulham Research Ethics Committee and participants gave written informed consent. Pseudo-continuous arterial spin labelling was performed on 493 subjects (age 55-90) from a tri-ethnic community-based cohort recruited in London. CBF was estimated using a simplified Buxton equation, with and without correction for Hct measured from blood samples. Differences in perfusion were compared, stratified by sex, ethnicity and diabetes. Results of Student's t tests were reported with effect size.

RESULTS

Hct adjustment decreased CBF estimates in all categories except white European men. The decrease for women was 2.7 (3.0, 2.4) mL/100 g/min) (mean (95% confidence interval (CI)), p < 0.001 d = 0.38. The effect size differed by ethnicity with estimated mean perfusion in South Asian and African Caribbean women found to be lower by 3.0 (3.6, 2.5) mL/100 g/min, p < 0.001 d = 0.56 and 3.1 (3.6, 2.5) mL/100 g/min), p < 0.001 d = 0.48, respectively. Estimates of perfusion in subjects with diabetes decreased by 1.8 (2.3, 1.4) mL/100 g/min, p < 0.001 d = 0.23) following Hct correction. Correction for individual Hct altered sample frequency distributions of CBF values, especially in women of non-European ethnicity.

CONCLUSION

ASL-derived CBF values in women, non-European ethnicities and individuals with diabetes are overestimated if calculations are not appropriately adjusted for individual Hct.

KEY POINTS

• CBF quantification from ASL using a fixed Hct of 43.5%, as recommended in the ISMRM white paper, may lead to erroneous CBF estimations particularly in non-European and female subjects. • Individually measured Hct values improve the accuracy of CBF estimation and, if these are not available, an adjusted value according to gender, ethnicity or diabetes status should be considered. • Hct-corrected ASL could be potentially important for CBF threshold decision making in the fields of neurodegenerative disease and neuro-oncology.

Minipig: Advantages and Disadvantages as a Model in Toxicity Testing

The choice of animal models for toxicity testing is usually based on convenience rather than validity for application in human beings. Attention must be paid to the similarities of the test system with those of humans so that extrapolations can be made with some margin of safety. Miniature swine offer many advantages in terms of being phylogenetically closer to humans and having many physiological similarities. The neonatal piglet is an excellent model for studies of perinatal toxicology and pediatrics because of its physiological resemblance to the human infant. The size of mature miniature swine, short reproductive cycle, ease of breeding, high prolificacy, large litter size, diversity of gene pool, early maturity, and adaptability to the experimental situation are advantages that do not exist in other species. All in all, the miniature swine is as yet an unappreciated and underutilized species for experimental purposes.

The effect of an e-health intervention designed to reduce prolonged occupational sitting on mean arterial pressure

OBJECTIVE

To evaluate the effect of a workplace health intervention designed to reduce prolonged occupational sitting on the mean arterial pressure (MAP) of desk-based employees.

METHODS

This randomized controlled trial involved an experimental group who received an e-health intervention and a control group who did not. The 13-week intervention passively prompted participants to stand and engage in short bouts of office-based physical activity by interrupting prolonged occupational sitting time periodically throughout the workday. Mean arterial pressure was measured at pretest and posttest.

RESULTS

Between pretest and posttest the experimental group significantly reduced their MAP, whereas MAP in the control group did not.

CONCLUSIONS

A workplace e-health intervention designed to reduce prolonged occupational sitting was effective in decreasing MAP in desk-based employees.

Retinopathy signs in people without diabetes: the multi-ethnic study of atherosclerosis

OBJECTIVE

To describe the prevalence of retinopathy and associations with cardiovascular risk factors in persons without diabetes in 4 racial/ethnic groups (white, black, Hispanic, and Chinese).

DESIGN

Population-based, cross-sectional study.

PARTICIPANTS

We included 6176 subjects aged 45-84 years without diabetes, selected from 6 United States communities.

METHODS

Fundus images were taken using 45° digital camera through dark-adapted pupils and were graded for retinopathy as defined by the Early Treatment Diabetic Retinopathy Study severity scale: microaneurysms, hemorrhages, cotton wool spots, intraretinal microvascular abnormalities, hard exudates, venous beading, and new vessels.

MAIN OUTCOME MEASURES

Retinopathy and the association with cardiovascular risk factors.

RESULTS

Prevalence rates of retinopathy in persons without diabetes were 12.5% overall, varying from 11.9% (white), 13.9% (black), 12.6% (Hispanic), to 17.2% (Chinese). Hypertension was strongly associated with retinopathy (odds ratio [OR], 1.47; 95% confidence interval [CI], 1.23-1.75). After adjusting for age, gender, race, and other parameters, smoking (OR, 1.50; 95% CI, 1.09-2.06) and increased internal carotid intima media thickness (OR, 1.22; 95% CI, 1.05-1.41) were associated with retinopathy. A range of serum inflammatory factors were examined, but none were found to be significant.

CONCLUSIONS

Retinopathy in persons without diabetes is common, varies with race/ethnicity, and associated with cardiovascular risk factors, including hypertension, smoking, and carotid artery intima media thickness.

15-year cumulative incidence and associated risk factors for retinopathy in nondiabetic persons

OBJECTIVE

To investigate the relationship of systemic factors to the 15-year cumulative incidence of retinopathy in nondiabetic persons in the Beaver Dam Eye Study.

METHODS

Included were 4699 persons, 43 to 86 years of age at baseline examination in 1988-1990 and with follow-up in 1993-1995 and/or 1998-2000 and/or 2003-2005. Stereoscopic color fundus photographs were graded to determine the presence of retinopathy. The main outcome measure was cumulative incidence of retinopathy accounting for competing risk of death or diabetes mellitus.

RESULTS

The 15-year cumulative incidence of retinopathy in the nondiabetic cohort was 14.2%. In multivariate analyses, older age (hazard ratio [HR] per age group, 1.13; 95% confidence interval [CI], 1.01-1.27), higher systolic blood pressure (HR per 10 mm Hg, 1.15; 95% CI, 1.07-1.20), presence of chronic kidney disease (HR, 1.51; 95% CI, 1.12-2.00), and wider retinal arteriolar diameter (HR per 10 μm, 1.17; 95% CI, 1.10-1.26) at baseline were associated with the incidence of retinopathy. In a separate model, the 15-year incidence of retinopathy was higher in those with uncontrolled hypertension compared with those who did not have hypertension (HR, 2.07; 95% CI, 1.51-2.83). There were no associations of body mass index, lipid levels, glycosylated hemoglobin level, smoking status, markers of inflammation, endothelial dysfunction and oxidative stress, and hematologic factors with retinopathy incidence.

CONCLUSIONS

These data show 2 modifiable factors, uncontrolled hypertension and chronic kidney disease, are related to an increased incidence of retinopathy in nondiabetic persons and show that control of blood pressure is associated with a lower risk of incident retinopathy compared with uncontrolled blood pressure.

Comparison of the retinal microvasculature in European and African-Caribbean people with diabetes

Diabetes aggravates the impact of elevated BP (blood pressure) on the microcirculation, and people of African ancestry with diabetes are more susceptible to microvascular damage than Europeans. In the present study, we investigated possible differences in the retinal microcirculation in people of European and African-Caribbean ethnicity with diabetes that might account for this. A total of 51 subjects with Type 2 diabetes (age 40–65 years; 25 male; 29 African-Caribbean) were studied. Clinic and 24 h ambulatory BP, and fasting glucose, insulin and lipids were measured. Digital retinal images were analysed using custom-written semi-automatic software to determine: LDR (length/diameter ratio) and AVR (arteriolar/venular diameter ratio), branching angles, vessel tortuosity and NT (number of terminal vessel branches). Arterioles were narrower in European people with diabetes than in African-Caribbean people with diabetes [mean (S.D.) arteriolar diameter, 76 (7) compared with 82 (11) μm respectively (P=0.03); arteriolar LDR, 28.1 (8.5) compared with 23.7 (7.0) respectively (P=0.046); and AVR, 0.66 (0.21) compared with 0.90 (0.36) respectively (P=0.028)]. Ethnic differences in arteriolar LDR, arteriolar diameter and AVR were not explained by differences in BP, but were attenuated by adjustment for the duration of diabetes. There was no significant relationship between BP and arteriolar narrowing in the group as a whole, although the relationship between arteriolar LDR and systolic BP was stronger in Europeans than African-Caribbeans [β=0.08 (0.07) compared with β=0.03 (0.06); P=0.03]. In conclusion, in the presence of diabetes, a relationship between BP and retinal arteriolar diameter was not evident and implies impaired small artery remodelling in the presence of diabetes. African-Caribbean people with diabetes have wider retinal arterioles and this could contribute to enhanced microvascular damage in this ethnic group.

Arterial pressures in a general practice

Systolic and diastolic readings of blood pressure were recorded for 5386 (2585 males and 2801 females) members of a general practice situated in and around Ballycastle, County Antrim. Polynomials to predict blood pressure from age were derived for systolic and diastolic pressures of males and females. Polynomials to predict blood pressure variance from age were derived for both systolic and diastolic pressure of each sex. Age-sex adjusted diastolic and systolic scores were calculated for each of the 5386 members of the practice using a technique similar to that reported by Hamilton et al. (1954 a, b).Parent-child correlations ranging from -0.21 to 0.17 were observed; however, when all sibships were considered together irrespective of size coefficients which were significantly greater than zero generally involved the mother of the child. No sib-sib correlation (all sibship sizes combined), except those involving twins exceeded the value 0.13. Husband-wife correlations were similar to the corresponding parent-offspring correlations when both husband and wife were aged 45 years or more. Generally speaking, the coefficients found in this study were lower than those of other workers and reasons are discussed why the estimates of the present paper may not be unbiased.

The prevalence of retinopathy in impaired glucose tolerance and recent-onset diabetes in the Diabetes Prevention Program

AIMS

Retinopathy is considered the complication most closely associated with and characteristic of diabetes mellitus. Hyperglycaemia below levels diagnostic of diabetes, so called pre-diabetes, is associated with a low prevalence of 'diabetic' retinopathy. However, few longitudinal studies of non-diabetic populations have performed repeated measures of glycaemia and screened for retinopathy to determine its occurrence in the non-diabetic population and the onset of retinopathy in new-onset diabetic patients. We determined the prevalence of retinopathy characteristically seen in diabetes in persons with impaired glucose tolerance and in patients with new-onset diabetes of known duration in the Diabetes Prevention Program (DPP) cohort.

METHODS

The DPP recruited persons with elevated fasting glucose (5.3-6.9 mmol/l) and impaired glucose tolerance, and no history of diagnosed diabetes, other than gestational diabetes not persisting after pregnancy. Seven-field, stereoscopic fundus photography was completed a mean of 3.1 years after the development of diabetes in 594 of 878 participants who had developed diabetes during the DPP, and in a random sample of 302 participants who remained non-diabetic.

RESULTS

Retinopathy consistent with diabetic retinopathy was detected in 12.6 and 7.9% of the diabetic and non-diabetic participants, respectively (P = 0.03, comparing prevalence in the two groups). Systolic blood pressure and HbA(1c) were higher at baseline in the diabetic participants who had retinopathy compared with the diabetic participants without retinopathy.

CONCLUSIONS

Retinopathy characteristic of diabetes is present in persons with elevated fasting glucose and impaired glucose tolerance and no known history of diabetes. The prevalence of retinopathy is significantly higher in persons who develop diabetes, even within 3 years of diagnosis.

From 1960s Evans County Georgia to present-day Jackson, Mississippi: an exploration of the evolution of cardiovascular disease in African Americans

Cardiovascular disease (CVD) is the No. 1 cause of mortality in the United States and it disproportionately affects African Americans. However, there are earlier reports that African Americans had significantly less CVD than whites. This racial discrepancy in CVD rates was noticed primarily for coronary heart disease (CHD). This issue was examined in the Evans County (Georgia) Cardiovascular Disease Study conducted in the 1960s. It showed that African American men had significantly lower rates of CHD than white men. Over the last couple of decades, the rates of CVD have been declining. However, the rate of decline of CVD in African Americans has not been equal to that seen in whites, such that African Americans now have a disproportionate share of CVD in the United States. In the 1990s, the Jackson Heart Study was designed to explore the reasons for the current racial discrepancy. This articles reviews the findings of the Evans County Study and explores various hypotheses for why CVD in African Americans has evolved from a disease from which African Americans may have been "protected" to one in which they shoulder a disproportionate burden.

Racial differences in the prevalence of hypertensive retinopathy

Few population-based data support the hypothesis that hypertensive retinopathy is more common in African Americans than in whites. We examined racial differences in the prevalence of and risk factors for hypertensive retinopathy in a population-based sample of 1860 African Americans and 7874 white persons, aged 49 to 73 years, without diabetes. Retinal photographs were taken of one randomly selected eye and evaluated for the presence of retinopathy (flame and blot-shaped retinal hemorrhages, microaneurysms, and soft exudates) according to standardized protocols by graders masked to participant characteristics. The prevalence of retinopathy was 2 times higher in African Americans than in whites (7.7% versus 4.1%, age- and gender-adjusted odds ratio [OR] 2.03, 95% confidence intervals [CI] 1.65, 2.49). After controlling for 6-year mean arterial blood pressure, use of antihypertensive medications and left ventricular hypertrophy by ECG criteria, the excess prevalence of retinopathy in African Americans was reduced by 40% (adjusted OR 1.61, 95% CI 1.26, 2.06). Further adjustment for other vascular risk factors, common carotid artery intima-media thickness, and serum creatinine levels reduced the excess prevalence in African Americans by another 13% (adjusted OR 1.48, 95% CI 1.08, 2.03). We conclude that hypertensive retinopathy is twice as frequent in African Americans compared with whites without diabetes and that the excess prevalence of retinopathy in African Americans is associated with blood pressure and severity of hypertension.

Retinal microvascular abnormalities and their relationship with hypertension, cardiovascular disease, and mortality

Retinal microvascular abnormalities, such as generalized and focal arteriolar narrowing, arteriovenous nicking and retinopathy, reflect cumulative vascular damage from hypertension, aging, and other processes. Epidemiological studies indicate that these abnormalities can be observed in 2-15% of the nondiabetic general population and are strongly and consistently associated with elevated blood pressure. Generalized arteriolar narrowing and arteriovenous nicking also appear to be irreversible long-term markers of hypertension, related not only to current but past blood pressure levels as well. There are data supporting an association between retinal microvascular abnormalities and stroke, but there is no convincing evidence of an independent or direct association with atherosclerosis, ischemic heart disease, or cardiovascular mortality. New computer-related imaging methods are currently being developed to detect the presence and severity of retinal arteriolar narrowing and other microvascular characteristics. When reliably quantified, retinal microvascular abnormalities may be useful as risk indicators for cerebrovascular diseases.

Methods for evaluation of retinal microvascular abnormalities associated with hypertension/sclerosis in the Atherosclerosis Risk in Communities Study

OBJECTIVE

To develop protocols to photograph and evaluate retinal vascular abnormalities in the Atherosclerosis Risk in Communities (ARIC) Study; to test reproducibility of the grading system; and to explore the relationship of these microvascular changes with blood pressure.

DESIGN

Population-based, cross-sectional study.

PARTICIPANTS

Among 4 examination centers, 11,114 participants (48-73 years of age) at their third triennial examination, after excluding persons with diabetes from this analysis.

METHODS

One eye of each participant was photographed by technicians with nonmydriatic fundus cameras. Reading center graders evaluated focal arteriolar narrowing, arteriovenous (AV) nicking, and retinopathy by examining slides on a light box and measured diameters of all vessels in a zone surrounding the optic disc on enhanced digitized images. To gauge generalized narrowing, vessel diameters were combined into central arteriolar and venular equivalents with formulas adjusting for branching, and the ratio of equivalents (A/V ratio) was calculated.

MAIN OUTCOME MEASURES

Retinal vascular abnormalities, mean arteriolar blood pressure (MABP).

RESULTS

Among 11,114 participants, photographs were obtained of 99%, with quality sufficient to perform retinal evaluations in 81%. In the 9040 subjects with usable photographs, A/V ratio (lower values indicate generalized arteriolar narrowing) ranged from 0.57 to 1.22 (median = 0.84, interquartile range = 0.10), focal arteriolar narrowing was found in 7%, AV nicking in 6%, and retinopathy in 4%. Because of attrition of subjects and limitation of methods, prevalence of abnormality was likely underestimated. Controlling for gender, race, age, and smoking status, these retinal changes were associated with higher blood pressure. For every 10-mmHg increase in MABP, A/V ratio decreased by 0.02 unit (P < 0.0001), focal arteriolar narrowing had an odds ratio (OR) of 2.00 (95% confidence interval [CI] = 1.87-2.14), AV nicking had an OR of 1.25 (95% CI = 1.16-1.34), and retinopathy had an OR of 1.25 (95% CI = 1.15-1.37). For any degree of generalized narrowing, individuals with focal narrowing had MABP approximately 8 mmHg higher than those without (P < 0.0001). Masked replicate assessment of a sample found the following reproducibility: for A/V ratio, correlation coefficient = 0.79 and median absolute difference = 0.03; for focal arteriolar narrowing, kappa = 0.45; for AV nicking, kappa = 0.61; and for retinopathy, kappa = 0.89.

CONCLUSION

Protocols have been developed for nonmydriatic fundus photography and for evaluation of retinal vascular abnormalities. Several microvascular changes were significantly associated with higher blood pressure; follow-up will show whether these are predictive of later cerebrovascular or cardiovascular disease independently of other known risk factors.

Maximum-likelihood generalized heritability estimate for blood pressure in Nigerian families

Elevated blood pressure (BP) is more common in relatives of hypertensives than in relatives of normotensives, indicating familial resemblance of the BP phenotypes. Most published studies have been conducted in westernized societies. To assess the ability to generalize these estimates, we examined familial patterns of BP in a population-based sample of 510 nuclear families, including 1552 individuals (320 fathers, 370 mothers, 475 sons, and 387 daughters) from Ibadan, Nigeria. The prevalence of obesity in this community is low (body mass index: fathers, 21.6; mothers, 23.6; sons, 19.2; and daughters=21.0 kg/m2). The BP phenotype used in all analyses was created from the best regression model by standardizing the age-adjusted systolic blood pressure (SBP) and diastolic blood pressure (DBP) to 0 mean and unit variance. Heritability was estimated by use of the computer program SEGPATH from the most parsimonious model of "no spouse and neither gender nor generation difference" as 45% for SBP and 43% for DBP. The lack of a significant spouse correlation is consistent with little or no influence of the common familial environment. However, the heritability estimate of <50% for both SBP and DBPs reinforces the importance of the nonshared environmental effect.

A review on ethnic differences in plasma triglycerides and high-density-lipoprotein cholesterol: is the lipid pattern the key factor for the low coronary heart disease rate in people of African origin?

Black people in the UK, in the Caribbean, and to a lesser extent in the USA, experience coronary heart disease events at different rates than white people. Despite having higher prevalence of hypertension, cigarette smoking and diabetes, black males have significantly lower coronary heart disease rates than white males, whereas no significant differences have been detected in females. The only known risk factor differences that could account for the difference in CHD rates are higher HDL cholesterol and lower triglycerides that are seen in blacks compared with whites. Obesity and, in particular abdominal obesity, seems to determine TG and HDL cholesterol levels: black males are less centrally obese than whites, while total adiposity and central distribution of fat is more predominant in black females compared with white females. We propose that the less degree of abdominal adiposity observed in black males is related with an increased anti-lipolytic effect of insulin, which could account for low triglycerides and high HDL cholesterol levels, and consequently explain the higher protection from coronary heart disease experienced by black males compared with whites and black females.

Racial differences in risk factors for atherosclerosis. The ARIC Study. Atherosclerosis Risk in Communities

This paper describes black/white differences in risk factors for atherosclerosis in the large multicenter Atherosclerosis Risk in Communities (ARIC) Project sponsored by the National Heart, Lung, and Blood Institute. It is based on data collected at baseline in ARIC's four geographically distinct clinical centers. Participants were randomly selected (4264 black and 11,479 white men and women, ages forty-five to sixty-four years at entry). There were striking differences in obesity between black and white women, higher fasting glucose and greater prevalence of diabetes in blacks, and lower high-density lipoprotein values in white men. Not unexpectedly, blood pressure in black participants exceeded that in whites. Clustering of multiple risk factors was more common in the black population. Conversely, prevalence of no risk factors was greatest among whites. In conclusion, while African-Americans and Caucasians share much the same group of risk factors for atherosclerosis, there are clinically important racial differences in emphasis.

The prevalence of hypertension in seven populations of west African origin

OBJECTIVES

This study was undertaken to describe the distribution of blood pressures, hypertension prevalence, and associated risk factors among seven populations of West African origin.

METHODS

The rates of hypertension in West Africa (Nigeria and Cameroon), the Caribbean (Jamaica, St. Lucia, Barbados), and the United States (metropolitan Chicago, Illinois) were compared on the basis of a highly standardized collaborative protocol. After researchers were given central training in survey methods, population-based samples of 800 to 2500 adults over the age of 25 were examined in seven sites, yielding a total sample of 10014.

RESULTS

A consistent gradient of hypertension prevalence was observed, rising from 16% in West Africa to 26% in the Caribbean and 33% in the United States. Mean blood pressures were similar among persons aged 25 to 34, while the increase in hypertension prevalence with age was twice as steep in the United States as in Africa. Environmental factors, most notably obesity and the intake of sodium and potassium, varied consistently with disease prevalence across regions.

CONCLUSION

The findings demonstrate the determining role of social conditions in the evolution of hypertension risk in these populations.

Incidence of hypertension and non-insulin dependent diabetes mellitus and associated risk factors in a rapidly developing Caribbean community: the St James survey, Trinidad

OBJECTIVE

To compare the incidence rates of hypertension and non-insulin dependent diabetes mellitus in relation to ethnicity and other characteristics in a rapidly developing community.

DESIGN

Prospective surveillance of a total community for five years.

SUBJECTS

Cohort of 2491 men and women aged 35 to 69 years (79% response), of African, Indian and "other' (mainly Afro-European) descent.

RESULTS

During surveillance, secular increases occurred in fasting blood glucose concentrations in both sexes and in body mass index (BMI) in men, with apparent secular reductions in systolic blood pressure in both sexes. Incidence rates of hypertension did not differ significantly with ethnicity, ranging between 33 and 41 per 1000 person-years in men and between 27 and 32 per 1000 person-years in women. In men, the incidence of diabetes (per 1000 person-years) in Indians (24) was significantly higher than in Africans (13) and others (11). In women, the diabetic incidence was similar to that for men in Indians (23) and Africans (14), but in others was twice that in men (21). In both sexes, weight gain was an important risk factor for hypertension, whereas risk of diabetes increased with BMI at baseline. The increased risk of diabetes in Indians among men was independent of baseline BMI and blood glucose.

CONCLUSION

Apart from the increased risk of diabetes in Indians, ethnicity had no significant influence on incidence rates of hypertension and diabetes in Trinidad. Secular increases in blood glucose in both sexes and in BMI in men probably contributed to the concurrent increase in mortality from coronary heart disease in this community.

Hypertensive retinopathy in Afro-Caribbeans and Europeans. Prevalence and risk factor relationships

The prevalence of hypertension is particularly high in people of black African descent throughout the world, and the consequences of hypertension, such as hypertensive heart and renal disease and stroke, are also more common. But there is little consensus on whether hypertensive retinopathy follows a similar pattern. We determined the prevalence of hypertensive retinopathy and its relationships with resting and ambulatory blood pressure in a population study of Afro-Caribbeans and Europeans aged 40 to 64 years in London, UK. Retinal photographs of 651 participants were graded for hypertensive retinopathy. Age- and sex-standardized prevalence of retinopathy was 11% (95% confidence interval, 8% to 14%) in Europeans and 21% (95% confidence interval, 16% to 26%) in Afro-Caribbeans (P < .001), respectively. This ethnic difference in prevalence was greatest in normotensive women (8% in Europeans versus 20% in Afro-Caribbeans, P < .001). Resting systolic pressure was 8 mm Hg higher in normotensive Afro-Carribean compared with European women, but this could not fully account for the ethnic difference in the prevalence of retinopathy. Examination of the different relationships of age and resting and ambulatory blood pressures with hypertensive retinopathy showed that these relationships were strongest in European women and weakest in Afro-Caribbean women. We conclude that hypertensive retinopathy is more common in Afro-Caribbeans, particularly women, and that ethnic differences in resting blood pressure cannot fully account for this. The relatively weak relationship between resting and ambulatory blood pressures and retinopathy in Afro-Caribbeans suggests that factors other than blood pressure determine the high rates of hypertensive retinopathy in this group.

Renal hemodynamics in essential hypertension. Racial differences in response to changes in dietary sodium

Previous studies have suggested striking racial differences in hypertension-related renal disease. To explore potential mechanisms responsible for these differences, we investigated changes in renal hemodynamics in white and black essential hypertensive patients in response to alterations in dietary sodium. Patients were untreated, age-matched, and blood pressure-matched white (n = 59) and black (n = 22) males with essential hypertension. Studies were conducted on an inpatient metabolic ward and included assessment of blood pressure, urinary sodium excretion, glomerular filtration rate, renal plasma flow, and renal blood flow after 5 days each of high and low salt diets. In response to high dietary salt intake, both white and black patients demonstrated significantly higher mean arterial pressure, renal plasma flow, and renal blood flow, and there were no racial differences in the changes in these parameters. However, whites and blacks differed significantly in glomerular filtration rate, with black hypertensive patients showing an increase in glomerular filtration rate (+17.3 +/- 5.3 mL/min per 1.73 m2, F = 7.586, P = .007) and white hypertensive patients showing no change (-0.2 +/- 3.3 mL/min per 1.73 m2) in response to high dietary sodium. These data demonstrate racial differences in the autoregulation of glomerular filtration rate in response to changes in dietary sodium. These differences suggest that glomerular hyperfiltration in response to a high salt diet may be a mechanism contributing to the racial disparity in hypertension-related renal disease.

Racial differences in cardiac structure and function in essential hypertension

OBJECTIVE

To assess racial differences in cardiac structure and function in patients presenting with previously untreated hypertension.

DESIGN

Untreated black patients with hypertension were compared with untreated white patients matched for age and sex. Both groups had similar body mass indices, blood pressures, and reported duration of hypertension.

SETTING

Cardiovascular risk factor clinic for outpatients.

SUBJECTS

36 men and 22 women with untreated essential hypertension.

MAIN OUTCOME MEASURES

Variables of heart structure and function on cross sectional and Doppler echocardiography.

RESULTS

The black patients had a significantly greater interventricular septal thickness (mean 1.23 (95% confidence interval 1.14 to 1.33) v 1.09 (1.02 to 1.16) cm; P = 0.02) and posterior wall thickness (mean 1.14 (1.07 to 1.22) v 0.96 (0.88 to 1.03) cm; P = 0.001) than the white patients, although left ventricular internal diameter was not significantly different (mean 4.90 (4.68 to 5.12) v 4.82 (4.64 to 5.01) cm; P = 0.59). This resulted in a significantly greater left ventricular mass index (mean 151 (137 to 164) v 120 (107 to 133) g/m2; P = 0.001) and relative wall thickness (mean 0.47 (0.43 to 0.51) v 0.40 (0.37 to 0.42) cm; P = 0.004) in the black patients. Comparison of Doppler measures of left ventricular diastolic function showed a significantly longer isovolumic relaxation time in black patients (mean 107 (98 to 116) v 92 (83 to 101) ms; P = 0.02) compared with white patients, although peak early to atrial filling ratios were similar in both groups (mean 1.14 (0.95 to 1.32) v 1.04 (0.94 to 1.15); P = 0.37).

CONCLUSION

Among previously untreated hypertensive patients, black subjects compared with white subjects have significantly higher left ventricular mass index and relative wall thickness, as well as more impairment of left ventricular function during diastole.

[Occupation and hypertension]

Scientific reports on Arterial Blood Hypertension for the period from 1970 to 1989 are reviewed, with special reference to its epidemiological focusing among workers. The knowledge gained and the theoretical and methodological advances associated with it are assessed.

Resting and ambulatory blood pressure differences in Afro-Caribbeans and Europeans

To investigate why mortality from stroke in people of Afro-Caribbean origin is twice the average for England and Wales, we examined 1166 European and Afro-Caribbean people in London. Age-standardized median systolic blood pressure was 6 mm Hg higher (128 versus 122 mm Hg) in Afro-Caribbean than European men and 17 mm Hg higher (135 versus 118 mm Hg) in Afro-Caribbean than European women. Migrants from West Africa and the Caribbean had similar blood pressures. Body mass index was higher in Afro-Caribbean than European women, accounting for 4 mm Hg of the systolic difference. Diabetes prevalence was 16% in Afro-Caribbeans and 5% in Europeans (P < .001), accounting for 1 mm Hg of the difference in systolic pressure in men and 2 mm Hg in women. In participants not taking antihypertensive medication, mean fall in ambulatory systolic pressure between daytime and nighttime, adjusted for resting blood pressures, was 24 mm Hg in Europeans and 18 mm Hg in Afro-Caribbeans (P = .05), and percent day-night fall in systolic blood pressure adjusted for resting systolic pressure was 17% in Europeans and 12% in Afro-Caribbeans (P < .05). This difference persisted when men and women and normotensive and hypertensive individuals were examined separately. We estimate that the differences in blood pressure between Afro-Caribbeans and Europeans may be enough to account for ethnic differences in stroke mortality in women but not men. The reasons for the high prevalence of hypertension and related morbidity in this and other populations of African descent remain to be established.

Restriction fragment length polymorphism of the apoprotein A-I-C-III gene cluster in control and stroke-prone white and black subjects: racial differences

The presence of known restriction fragment length polymorphisms in the apoprotein A-I-C-III gene cluster, which encodes their respective apoproteins, was investigated using the restriction enzymes Sac I and Pst I to determine the potential role of genetic variations for stroke risk in an American population.

Ninety-eight subjects (70 white, 28 black subjects), both normal controls with no carotid stenosis and those with carotid stenosis believed at risk for stroke, defined as showing stenosis focally or diffusely at that site, composed the study population.

Sac I polymorphic S2 allele frequency was higher in stroke-risk groups, whereas Pst I polymorphic P2 allele frequency was similar in control and stroke-risk groups. Significantly higher levels of serum cholesterol, triglycerides, and low density lipoprotein (p less than 0.05) and significantly lower levels of high density lipoprotein (p less than 0.05) were observed in stroke-risk groups with diffuse stenosis. Results of our study with the two racial groups show the following: the frequency of Sac I polymorphism was significantly higher in American black compared with American white subjects (chi 2 = 3.92, p less than 0.05). Among serum lipids, triglycerides were significantly higher in white compared with black subjects (p less than 0.05). In white subjects, carotid artery stenosis was associated with significantly elevated total cholesterol and low density lipoprotein (p less than 0.01) but not with Sac I polymorphism. In black subjects the converse was observed, namely, the Sac I polymorphic S2 allele seemed to be associated with carotid bifurcation stenosis but did not reach statistical significance because of the small number of subjects. In addition, Sac I polymorphism did not correlate with any lipid profile. Pst I polymorphism was not associated with any lipid profile or carotid artery stenosis abnormalities.

Our results indicate that carotid artery stenosis identifies white subjects with increased plasma total cholesterol and low density lipoprotein, an atherogenic profile, but not with Sac I polymorphism. These findings suggest that carotid bifurcation stenosis in white subjects is associated with an atherogenic lipid profile but not with apoprotein A-I-C-III restriction fragment length polymorphisms. In black subjects, Sac I polymorphism seems to identify those individuals with significant carotid stenosis, a necessary precursor to atherothrombotic brain infarction, but not those with elevated total cholesterol, elevated low density lipoprotein, and/or reduced high density lipoprotein. These results suggest that Sac I polymorphism may identify black subjects at increased risk for atherothrombotic brain infarctions.

Persistent hypertension after prenatal cocaine exposure

Multiple blood pressure readings were obtained with time in 12 infants with documented in utero exposure to cocaine. Approximately half had hypertension or high-normal blood pressure with no evidence of renal, cardiovascular, or endocrinologic abnormalities.

End-stage renal disease in US minority groups

Medicare's End-Stage Renal Disease (ESRD) Program makes renal replacement services accessible for the majority of Americans with renal failure. National data from Medicare demonstrate complex and variable patterns of use of renal replacement services among US racial and ethnic groups. The black population has consistently suffered from a greater than 3.5-fold higher rate of treated ESRD than has the white population. The rates of hypertensive, diabetic, and glomerulopathic ESRD are all substantially greater in blacks than in whites, and hypertension has accounted for a far greater proportion of ESRD in blacks than any other diagnosis. There is a paucity of national data on the occurrence of ESRD in Hispanic Americans. However, data from Texas strongly suggest that the incidence rate of treated ESRD is much higher in Mexican Americans than in non-Hispanic whites. Higher rates are apparent for each of the three most important causes of ESRD: hypertension, diabetes, and glomerulonephritis. Native Americans experience ESRD at a rate intermediate between those of whites and blacks, but their rate of diabetic ESRD is higher than in either blacks or whites. However, considerable diversity exists among Native American tribal groups. Significant barriers to the acquisition of preventive care have been identified, especially for blacks. While these barriers to preventive care are accompanied by a significantly impaired health status of the black American population, a specific causal relationship between impaired access to care for blacks and their predisposition to ESRD has not been established.

Is the decrease in arterial pressure the sole factor for reduction of left ventricular hypertrophy?

The increasing evidence that identifies left ventricular hypertrophy (LVH) as a powerful prognostic factor leads to the question whether or not reduction of LVH is a desirable goal of antihypertensive therapy and, moreover, whether a decrease in arterial pressure per se is the only or the main determinant for reduction of LVH. An analysis of the underlying pathogenic mechanisms suggests the presence of multiple interacting pathogenic factors in the development of LVH. Conversely, disparate rates of reduction of LVH with various antihypertensive drugs as well as conflicting results in different hypertensive patients point to the existence of blood pressure-independent factors influencing reduction of LVH.

Regression of left ventricular hypertrophy in "previously untreated" hypertensive blacks after 6 months of blood pressure reduction with alpha- and beta-adrenergic blockade and thiazide therapy

In 10 hypertensive black patients who were "previously untreated" (defined as no antihypertensive therapy for a minimum of 12 months prior to enrollment) and who had LVH (defined by an increase in both wall thickness and echocardiographically determined LV mass), we studied the effects of treatment with either labetalol, an alpha- and beta-adrenergic blocker (three patients), or labetalol plus hydrochlorothiazide (seven patients). After 6 months of effective antihypertensive therapy, there was a 12% decrease in LV mass for the entire group. However, the extent of LVH regression was highly variable among individual patients.

Comparison of blood lipids and blood pressure in black and white collegiate male athletes

Blood lipids, lipoproteins, and blood pressure (BP) were examined in 74 black and 93 white male NCAA Division I-A collegiate football athletes. Subjects were involved in resistance training and anaerobic running and all ate at the same training table. All measurements were done in the morning following a 12 hour fast. No significant differences were found in mean systolic (128 mm Hg) or diastolic (77 mm Hg) BPs. Blacks and whites were similar in age, height, weight, V̇O_2max estimated from a 12 minute run test, total serum cholesterol, and low-density lipoprotein cholesterol (LDL-C). However, the black athletes had significantly (P < 0.01) lower serum triglycerides, total cholesterol to HDL-C ratio, and higher high-density lipoprotein cholesterol (HDL-C) compared to whites. In a subgroup of 34 subjects, there were no differences in dietary fat, carbohydrate, cholesterol, sodium, potassium, calcium, or fiber intake. These data suggest a race-related difference in some blood lipids-lipoproteins without a concomitant difference in BP within a group of young adult male athletes.

By how much does dietary salt reduction lower blood pressure? I--Analysis of observational data among populations

OBJECTIVE

To estimate the quantitative relation between blood pressure and sodium intake.

DESIGN

Data were analysed from published reports of blood pressure and sodium intake for 24 different communities (47 000 people) throughout the world.

MAIN OUTCOME MEASURE

Difference in blood pressure for a 100 mmol/24 h difference in sodium intake. Allowance was made for differences in blood pressure between economically developed and undeveloped communities to minimise overestimation of the association through confounding with other determinants of blood pressure.

RESULTS

Blood pressure was higher on average in the developed communities, but the association with sodium intake was similar in both types of community. A difference in sodium intake of 100 mmol/24 h was associated with an average difference in systolic blood pressure that ranged from 5 mm Hg at age 15-19 years to 10 mm Hg at age 60-69. The differences in diastolic blood pressure were about half as great. The standard deviation of blood pressure increased with sodium intake implying that the association of blood pressure with sodium intake in individuals was related to the initial blood pressure--the higher the blood pressure the greater the expected reduction in blood pressure for the same reduction in sodium intake. For example, at age 60-69 the estimated systolic blood pressure reduction in response to a 100 mmol/24 h reduction in sodium intake was on average 10 mm Hg but varied from 6 mm Hg for those on the fifth blood pressure centile to 15 mm Hg for those on the 95th centile.

CONCLUSIONS

The association of blood pressure with sodium intake is substantially larger than is generally appreciated and increases with age and initial blood pressure.

Hemodynamic differences between black patients and white patients with essential hypertension. State of the art lecture

Physiological studies reported from our laboratory over the past several years have been reviewed and support epidemiological reports indicating that hypertensive cardiac and vascular disease runs a more severe course in the black patient. Although comparison of systemic hemodynamics failed to demonstrate that, for any level of arterial pressure, the magnitude of total peripheral resistance (which is the hemodynamic hallmark of hypertensive disease) differed between black patients and white patients, there are more subtle differences that were ascertained. Thus, although intravascular (plasma) volume contracts as arterial pressure and total peripheral resistance increase in both racial groups, this relation may differ quantitatively. At least in some black patients (43%), intravascular volume may be more expanded; in these patients, this relation is less closely correlated with the renopressor system (i.e., plasma renin activity). Moreover, these studies indicated that, at any level of arterial pressure, cardiac (left ventricular mass and posterior wall thickness) and renal hemodynamic involvement is more severe in the black patient. These findings point to important differences that operate in black patients and white patients with essential hypertension. With further study, these findings may be translated into more specific antihypertensive therapeutic implications for patients of both racial groups with essential hypertension.

The response of the light reflex of retinal vessels to reduced blood pressure in hypertensive patients

The response of retinal arteries and veins to 3 months of antihypertensive medication was studied in 10 patients (39-56 years old) with essential hypertension. We used computerized microdensitometry on fundus photographs, a technique allowing for objective and simultaneous measures of the caliber of blood columns and the width and intensity of their central 'light reflex'. A moderate lowering of diastolic and systolic blood pressures (P less than 0.001) resulted in a significant reduction in the intensity of reflection from retinal arteries (38.6%; P less than 0.005). An increase in the width of the blood column (2.8%; n.s.) and the reflex (8.6%; n.s.) was indicated. Traditionally, changes in light reflectivity has been associated with arteriosclerosis of the vessel wall. The study shows, however, that the vascular reflex is most sensitive to changes in the systemic blood pressure. This signals a need for critical reviewal of interpretation and usefulness of classical grading systems of ophthalmoscopic signs of hypertensive retinopathy.

Autonomic function in hypertension. Are there racial differences?

Previous biochemical assessment of sympathetic nervous system activity including plasma catecholamines, plasma renin activity, and plasma dopamine-beta-hydroxylase levels has suggested racial differences in the contribution of the sympathetic nervous system to the pathogenesis or maintenance of hypertension. We, therefore, performed physiological and pharmacological studies in white and black subjects with essential hypertension and their age-matched normotensive counterparts to assess autonomic and sympathetic nervous system function. One hundred one male subjects (47 white hypertensive, 17 black hypertensive, 22 white normotensive, and 15 black normotensive subjects) were evaluated for baroreceptor reflex sensitivity to low-pressure (amyl nitrite inhalation) and high-pressure (phenylephrine infusion) stimuli; cold pressor test heart rate and blood pressure responses; and blood pressure response to phentolamine alpha-adrenergic blockade. Hypertensive subjects exhibited an increase in resting heart rate, a decrease in baroreceptor reflex sensitivity, and an exaggerated decline in mean arterial pressure in response to phentolamine. These abnormalities were present to a comparable degree in black and white hypertensive subjects. Cold pressor testing revealed greater increases in heart rate in blacks as compared with whites; however, this racial difference was present regardless of blood pressure status, occurring in black normotensive and black hypertensive subjects to a comparable degree. Cold pressor test blood pressure increments were similar in the four groups. We conclude that both white hypertensive and black hypertensive subjects demonstrate similar abnormalities in autonomic and sympathetic nervous system function including blunting of baroreceptor reflex sensitivity and an increased alpha-adrenergic receptor participation in blood pressure maintenance. The results do not suggest major racial differences in autonomic pathogenetic mechanisms in hypertension.

Essential hypertension in blacks: epidemiology, characteristics, and possible roles of racial differences in sodium, potassium, and calcium regulation

Racial differences in the regulation of Na+, K+, and Ca2+ have been shown both at the systemic and cellular levels. These include a higher incidence of "salt sensitivity," lower urinary K+ excretion, lower plasma renin activity, and higher circulating levels of immunoreactive parathyroid hormone and 1.25 dihydroxyvitamin D in blacks than in whites. Blacks exhibit a higher erythrocyte Na+ concentration, coupled with a lower maximal initial reaction velocity of erythrocyte Na,K-ATPase. Blacks also appear to differ from whites in erythrocyte Na+, K+ cotransport and Na-Li countertransport. Moreover, they show a higher activity of the Na(+)-H+ antiport in skin fibroblasts and a greater response of cellular Ca2+ signaling to agonists in serum. Mechanisms linking some of these racial differences in ionic metabolism to the increased propensity of blacks to develop essential hypertension are proposed, and the epidemiology and characteristics of this disease in blacks are reviewed.

A study of urinary and intracellular sodium and potassium, renin, aldosterone, and hypertension in blacks and Indians in Natal

The prevalence of hypertension in the urban black population in Sub-Saharan Africa is high and varies from 20% to 25%. In contrast, the prevalence of hypertension in the rural black is relatively low. In Natal the prevalence of hypertension in a large metropolitan city, Durban, is 25% in the adult Zulu, 17.2% in whites, and 14.2% in Indians. The prevalence of hypertension in the rural Zulu of Natal is 10%. Work on the pathogenesis of hypertension in the Zulu and Indian ethnic groups related to renin, aldosterone, dietary sodium and potassium, and intracellular sodium and potassium was virtually nonexistent. This review paper summarizes the salient features that were found.

Ideology in medical science: class in the clinic

The class character of medicine is most easily discerned in the inequitable organization of health services. Capital's shaping of the patterns of disease and our medical/scientific responses is less apparent but equally strong. We illustrate this point by reviewing some recent history of cardiovascular diseases and therapies. Hitherto unknown afflictions have become commonplace. Our diagnostic and therapeutic concepts are the crystallization of a long history of scientific effort--an effort dominated and directed by capitalist imperatives. The work of the clinician rests on this scientific substrate, and recognition or rejection of its class nature provides a potential basis for a new medical science but not the needed results. The socialist transformation of medicine will require a recognition of the capitalist specificity of current science, and the painstaking construction of alternative modes of thought.

Epidemiology of hypertension in older patients

There are few studies devoted specifically to the epidemiology of older hypertensive patients, although some information has been obtained from broader trials in which either the study populations have become older or an older subgroup has been identified. Three areas have been addressed: the changes of blood pressure with age; the prevalence of hypertension in older persons; and the risks of elevated blood pressure in elderly patients. It has been found that blood pressure, especially systolic pressure, increases with age. Consequently, hypertension is extremely prevalent in this age group, affecting 65 percent or more of those over 65 years old, and the phenomenon of isolated systolic hypertension is common. Whereas in the past many physicians treating the elderly have regarded hypertension in these patients as normal and acceptable, or even helpful in ensuring adequate organ perfusion, elevated blood pressure in the elderly is far from benign. Older hypertensive patients' risks of cardiovascular complications and death are from two to five times that of normotensive persons. Treatment of diastolic hypertension in older patients can be expected to delay the onset of cardiovascular disease and improve the quality of life. Hopefully, this will prove to be true for isolated systolic hypertension as well.