A.E. Schutte

Validation of the Finometer device for measurement of blood pressure in black women

The improved Finapres apparatus, known as the Fino-meter, measures finger blood pressure noninvasively on a beat-to-beat basis and gives waveform measurements similar to intra-arterial recordings. The Finometer measures brachial pressure and corrects for finger pressure accordingly. It also corrects for the hydrostatic height of the finger with respect to the heart level. The objective was to validate the Finometer according to the revised British Hypertension Society (BHS) protocol and the criteria of the Association for the Advancement of Medical Instrumentation (AAMI). We carried out a main validation test using a subject group of 102 black women, which was also divided into smaller groups, namely 24 hypertensives, 25 obese normotensive and 35 lean normotensive women. Finometer and mercury sphygmomanometer blood pressure (BP) measurements were taken early in the morning before breakfast, after the subjects stayed overnight in a research unit. Within the whole subject group, the Finometer satisfied the AAMI criteria for accuracy and achieved an overall A/B grading according to the BHS criteria. The sphygmomanometer measurements were 128±20/78±12 mmHg compared to 130±20/78±11 mmHg for the Finometer. The average differences between the mercury sphygmomanometer and Finometer readings for systolic and diastolic BP were, respectively, −1.83±6.8 and 0.88±7.5. Systolic readings of the Finometer device differed by less than 5 mmHg for 64%, by less than 10 mmHg for 86% and differed by less than 15 mmHg for 96% of all readings. A total of 63% of all diastolic readings of the Finometer by less than 5 mmHg, 85% by less than 10 mmHg and 94% of all readings differed by less than 15 mmHg. On the basis of these results, the Finometer device satisfied the validation criteria of AAMI and received an A/B grading according to the BHS protocol. It can therefore be recommended for measurements in the clinical set-up and for research purposes.

The Finnish Diabetes Risk Score Is Associated with Insulin Resistance and Progression towards Type 2 Diabetes

OBJECTIVE The Finnish Diabetes Risk Score (FINDRISC) questionnaire is a practical screening tool to estimate the diabetes risk and the probability of asymptomatic type 2 diabetes. In this study we evaluated the usefulness of the FINDRISC to predict insulin resistance in a population at increased diabetes risk. DESIGN Data of 771 and 526 participants in a cross-sectional survey (1996) and a cohort study (1997-2000), respectively, were used for the analysis. Data on the FINDRISC and oral glucose tolerance test parameters were available from each participant. The predictive value of the FINDRISC was cross-sectionally evaluated using the area under the curve-receiver operating characteristics method and by correlation analyses. A validation of the cross-sectional results was performed on the prospective data from the cohort study. RESULTS The FINDRISC was significantly correlated with markers of insulin resistance. The receiver operating characteristics-area under the curve for the prediction of a homeostasis model assessment insulin resistance index of more than five was 0.78 in the cross-sectional survey and 0.74 at baseline of the cohort study. Moreover, the FINDRISC at baseline was significantly associated with disease evolution (P < 0.01), which was defined as the change of glucose tolerance during the 3 yr follow-up. CONCLUSIONS The results indicate that the FINDRISC can be applied to detect insulin resistance in a population at high risk for type 2 diabetes and predict future impairment of glucose tolerance.

Conventional and behavioral risk factors explain differences in sub-clinical vascular disease between black and Caucasian South Africans: the SABPA study

OBJECTIVES There is an emerging burden of cardiovascular disease among urban black Africans in South Africa, which has been largely explained by the transition from traditional African lifestyles to more westernized behavior. We examined the role of health behaviors in explaining the excess burden of sub clinical vascular disease seen in black Africans compared to Caucasians. METHODS This was a cross-sectional study, comprising of urban African teachers (n=192 black, 206 Caucasian) working for one of the four Kenneth Kaunda Education districts in the North West Province, South Africa. Conventional cardiovascular risk factors, 24 h ambulatory blood pressure and objectively measured physical activity (Actical® accelerometers), smoking (confirmed by serum cotinine), and alcohol (serum gamma glutamyl transferase) were assessed. The main outcome was a marker of sub-clinical vascular disease, mean carotid intima media thickness (mCIMT), measured using high resolution ultrasound. RESULTS Compared with Caucasians, the black Africans demonstrated higher mCIMT (age and sex adjusted β=0.044, 95% CI, 0.024-0.064 mm). The blacks also had higher 24h systolic and diastolic blood pressure, triglycerides, adiposity, and C-reactive protein. In addition, blacks were less physically active (790.0 kcal/d vs 947.3 kcal/d, p<0.001), more likely to smoke (25% vs 16.3%, p=0.002), and demonstrated higher alcohol abuse (gamma glutamyl transferase, 66.6 μ/L vs 27.2 μ/L, p<0.001) compared with Caucasians. The difference in mCIMT between blacks and Caucasians was attenuated by 34% when conventional risk factors were added to the model and a further 18% when health behaviors were included. CONCLUSION There is an excess burden of sub clinical vascular disease seen in black Africans compared to Caucasians, which can be largely explained by health behaviors and conventional risk factors.

Factor analysis of possible risks for hypertension in a black South African population

To date only a small number of studies have investigated the pattern of associations within a set of hypertension risks. The objective of this study was therefore to examine the interrelation of main hypertension risks in an African population by using factor analysis in order to detect underlying risk patterns. Subjects aged 16–70 years (N=963) were recruited from 37 randomly selected sites throughout the North West Province during 1996–1998. Exclusion criteria were pregnancy, lactation, casual visitors, drunkenness and treatment for chronic diseases, such as hypertension. Subjects with blood pressures exceeding 140/90 mmHg were classified as hypertensive. Children aged 10–15 years were also recruited from 30 randomly selected schools during 2000–2001 (N=694). Children were classified as hypertensive when an average systolic or diastolic blood pressure greater than or equal to the 90th percentile for age and sex was encountered, while correcting for height. The following hypertension risks were measured: urbanisation, obesity, plasma fibrinogen, lipids, insulin, serum gamma glutamyl-transferase, dietary intake, smoking and alcohol consumption.From 23 risks the factor analysis disclosed five factors that explained 56.2% of the variance in the male and 43.5% of the variance in the female group: an urban malnutritional phenomenon, the metabolic syndrome X, a hypercholesterolaemic and obesity complex, an alcoholic hypertriglyceridaemia, and central and peripheral cardiovascular hypertensive effects. In conclusion, South Africans migrating from rural to urban areas adapt to a new lifestyle with numerous risks, resulting in conditions like malnutrition, the metabolic syndrome X, dyslipidaemia, alcoholism, obesity and increased peripheral vascular resistance. For successful prevention of hypertension in a population in transition, a whole risk pattern should be corrected, rather than an individual risk by implementing lifestyle modification programmes.

Associations between reactive oxygen species, blood pressure and arterial stiffness in black South Africans: the SABPA study

Many mechanisms, including oxidative stress, contribute to hypertension. This study investigated the possible associations between oxidative stress, blood pressure and arterial stiffness in black South Africans. Ambulatory blood pressure measurements were taken for 101 black South African men and 99 women. The stiffness indices included ambulatory arterial stiffness index (AASI) and pulse pressure (PP). Reactive oxygen species (ROS) levels (P<0.0001) were higher in the African women compared with men. ROS levels were also higher in hypertensive compared with normotensive men. The 24 h systolic blood pressure (SBP; P<0.01), 24 h diastolic blood pressure (DBP; P<0.0001) and pulse wave velocity (PWV; P<0.01) were significantly higher in African men compared with women. There were unadjusted positive associations of 24 h SBP (r=0.33; P=0.001), 24 h DBP (r=0.26; P=0.008) and 24 h PP (r=0.29; P=0.003) with ROS in African men only. A positive association between AASI and ROS existed only in hypertensive men (r=0.27; P=0.035), but became nonsignificant (B=0.0014; P=0.14) after adjustments. Adjusted, positive associations of 24 h SBP (B=0.181; P=0.018) and 24 h PP (B=0.086; P=0.050) with ROS were again only evident in African men. ROS is positively associated with SBP and PP in African men, suggesting that increased ROS levels may contribute to hypertension in this population group.

Dietary risk markers that contribute to the aetiology of hypertension in black South African children: the THUSA BANA study

Although clinical hypertension occurs less frequently in children than in adults, ample evidence supports the concept that the roots of essential hypertension extend back to childhood. Since little is available in the literature on causal dietary factors of hypertension in children, this study hypothesised that certain dietary factors can be identified as risk markers that might contribute to the aetiology of hypertension in black children. Children aged 10–15 years were randomly selected from 30 schools in the North West Province from 2000 to 2001. These children comprised 321 black males and 373 females from rural to urbanised communities, of which 40 male and 79 female subjects were identified with high-normal to hypertensive blood pressure. Blood pressure was measured with a Finapres apparatus and data were analysed with the Fast Modelflo software program to provide systolic, diastolic and mean blood pressure. A 24-h dietary recall questionnaire and weight and height measurements were taken. In a stepwise regression analysis, the following variables were significantly associated (P⩽0.05) with blood pressure parameters of hypertensive males: biotin, folic acid, pantothenic acid, zinc and magnesium. Energy, biotin and vitamin A intakes were significantly associated with blood pressure parameters of hypertensive females. No significant dietary markers were indicated for any of the normotensive groups. Dietary intakes of all of these nutrients were well below the dietary reference intakes. In conclusion, the dietary results coupled with the cardiovascular parameters of this study identified folic acid and biotin as risk markers that could contribute to the aetiology of hypertension in black persons. The low intakes of these nutrients, among others, is a matter of serious concern, as is the increasing tendency towards urbanisation.

Cardiovascular effects of oral supplementation of vitamin C, E and folic acid in young healthy males

Numerous observational studies showed associations of antioxidants (vitamins C and E) and folate intake with a reduced risk of cardiovascular disease, but randomized controlled clinical trials have generally not supported this hypothesis. The objective of this study was to investigate the effects of a daily dosage of 1000 mg vitamin C, 800 mg vitamin E, and 10 mg folate on markers of vascular function in 31 young healthy male adults. Cardiovascular values after a 12-week vitamin (14 subjects) or placebo (17 subjects) intervention were compared to baseline values. Cardiovascular parameters (blood pressure, stroke volume, heart rate, cardiac output, vascular resistance, arterial compliance) were measured continuously after an overnight fast under controlled circumstances with a Finometer device. Our main finding was a significant decrease (p = 0.03) in systolic blood pressure in the experimental group. No statistically significant changes were observed within other cardiovascular variables of the experimental group, but possible beneficial decreases in diastolic blood pressure and increases in arterial compliance after 12 weeks of vitamin supplementation were indicated. In conclusion, beneficial effects of antioxidants and folate were observed probably because the supplementation was used by young healthy subjects under carefully controlled conditions.

Prolactin, testosterone and cortisol as possible markers of changes in cardiovascular function associated with urbanization

People living in large informal settlements in South Africa showed a significant increase in cardio/cerebrovascular disease. This study was undertaken to compare the cardiovascular and endocrine parameters of urbanized and rural black female and males. The hormone levels such as prolactin, cortisol and testosterone may also change with urbanization and could make a contribution to the high rate of hypertension. For this study, 1202 black subjects were selected from 37 randomly selected rural and urbanized settlements. Resting blood pressure was recorded with a Finapres apparatus. Cardiac output, stroke volume, heart rate, total peripheral vascular resistance and compliance had been obtained with the Fast Modelflow software program. An acute laboratory stressor (hand dynamometer exercise) was applied to challenge the cardiovascular system and the measurements were repeated. Blood sampling was done and hormone levels were determined by biochemical analyses. For females, significant lower levels of cortisol were found in the urban strata in comparison with the rural strata. The testosterone levels were significantly lower and the prolactin levels significantly higher for females in the informal settlements compared with the rural strata. It is noticeable that most cardiovascular parameters showed the highest changes with the application of the stressor in the informal settlement strata and the lowest in people living on farms for both male and female. The prolactin levels in males are significantly higher in the informal settlement stratum. Subjects living in informal settlements showed a noticeable endocrine pattern of ongoing stress that can be associated with changes in the cardiovascular parameters with urbanization. This can partly explain the reported high rate of cardio/cerbrovascular disease in black South Africans living in informal settlements.

Classifying Africans with the Metabolic Syndrome

This study was aimed to compare prevalences of the metabolic syndrome in Africans using five definitions as proposed by the World Health Organization (WHO), the European Group for the Study of Insulin Resistance (EGIR), the National Cholesterol Education Program Expert Panel on Detection, Evaluation, and Treatment of High Blood Cholesterol in Adults [Adult Treatment Panel (ATPIII)], the American College of Endocrinology (ACE), and the International Diabetes Federation (IDF). A further objective was to identify difficulties in classifying Africans with the metabolic syndrome and to suggest specific areas where criteria adjustments for identifying Africans should be made. A case-case-control cross-sectional study involved 102 urban African women. Except for microalbumin data, all data necessary for classification of the metabolic syndrome were collected, including fasting and 2-h glucose and insulin, anthropometric measurements, blood pressure, and lipids. The metabolic syndrome prevalences ranged from 5.4% (EGIR), 15.7% (ATPIII), >or=19.4% (WHO), 24.8% (IDF) to 25.5% (ACE). Only 2.9% (n=3) had a triglyceride level >or=1.69 mmol/l, but 58.8% (n=60) had a HDL-level <1.29 mmol/l, whereas 27% (n=26) were insulin resistant, 22.3% (n=21), had a blood pressure >or=140/90 or used hypertension medication. It seems as if the classification of hypertension, insulin resistance and hyperglycemia might have been adequate, but body composition and dyslipidemia criteria need adjustment for Africans. Since neither definition seems completely suitable for Africans it is suggested that clinical emphasis should rather be on treating any specific cardiovascular disease risk factor that is present, than on diagnosing a patient with the metabolic syndrome.

Endothelial activation and cardiometabolic profiles of treated and never-treated HIV infected Africans

OBJECTIVE The role the human immunodeficiency virus (HIV) and antiretroviral treatment on endothelial activation, and the subsequent relationship with cardiovascular disease, is not well understood. We investigated endothelial activation, inflammatory and cardiometabolic profiles, and measures of vascular structure and function of 66 antiretroviral treated (ART), 78 never-treated (no-ART) HIV infected and 165 HIV free Africans. METHODS Blood samples were obtained for biochemical analysis and blood pressure, pulse wave velocity (PWV) and carotid intima-media thickness (IMT) measurements were performed. RESULTS The HIV infection duration was at least five years and the treatment 2.86±0.13 years. The intracellular adhesion molecule (ICAM) and vascular cell adhesion molecule (VCAM) levels were elevated in the HIV infected groups compared to the controls. The odds of higher adhesion molecule levels were increased when HIV infected (especially in the no-ART group); OR no-ART vs. no-HIV: ICAM 3.92 (2.2-7.0); VCAM 16.2 (7.5-35). ICAM and VCAM associated with HIV status and interleukin-6 (IL-6) in the total group (all p<0.01). In both HIV infected groups VCAM associated inversely with CD4 counts (no-ART: β=-0.28, p=0.01; ART: β=-0.22, p=0.07) and TC (no-ART: β=-0.36, p<0.01; ART: β=-0.27, p=0.03). The ART group had an unfavourable lipid profile compared to the no-ART group. The inflammatory markers (C-reactive protein (CRP) and IL-6), PWV and IMT did not differ between the three groups. CONCLUSION HIV infected Africans showed endothelial activation when compared to HIV free controls. The endothelial activation was not accompanied by increased inflammation (as measured with CRP and IL-6), arterial stiffness or sub-clinical atherosclerosis.