The association between seven-day objectively measured habitual physical activity and 24 h ambulatory blood pressure: the SABPA study.

Few studies have examined objective physical activity in relation to 24 h ambulatory blood pressure (BP). We aimed to assess the association of 7-day objectively measured habitual physical activity with ambulatory BP in a sample of African and Caucasian school teachers (n=216, age 49.7 years) from the sympathetic activity and blood pressure in Africans prospective cohort study. Hypertension (ambulatory systolic BP⩾130 and/or diastolic BP⩾80 mm Hg) was prevalent in 53.2% of the sample, particularly in black Africans. The hypertensive group spent significantly more awake time in sedentary activity (51.5% vs 40.8% of waking hours, P=0.001), as well as doing less light- (34.1% vs 38.9%, P=0.043) and moderate-intensity (14.0% vs 19.7%, P=0.032) activities compared with normotensives, respectively. In covariate adjusted models, light-intensity activity time was associated with lower 24 h and daytime ambulatory systolic BP (ß=-0.15, 95% confidence interval (CI): -0.26, -0.05, P=0.004; ß=-0.14, CI: -0.24, -0.03, P=0.011) and diastolic BP (ß=-0.14, CI: -0.25, -0.03, P=0.015; ß=-0.13, CI: -0.24, -0.01, P=0.030), as well as resting systolic BP (ß=-0.13, CI: -0.24, -0.01, P=0.028). Sedentary time was associated only with 24 h systolic BP (ß=0.12; CI: 0.01, 0.22), which was largely driven by night-time recordings. Participants in the upper sedentary tertile were more likely to be 'non-dippers' (odds ratio=2.11, 95% CI: 0.99, 4.46, P=0.052) compared with the lowest sedentary tertile. There were no associations between moderate to vigorous activity and BP. In conclusion, objectively assessed daily light physical activity was associated with ambulatory BP in a mixed ethnic sample.

Profile of the female athlete triad among elite Kenyan endurance athletes and non-athletes

Women participating in endurance sports are at risk of presenting with low energy availability (EA), menstrual dysfunction (MD), and low bone mineral density (BMD), collectively termed the female athlete triad (FAT or TRIAD). Therefore, the purpose of the study was to determine the profile of the TRIAD among elite Kenyan female athletes and among non-athletes. There were 39 participants (athletes: 25, non-athletes:14) who provided the data for this study. Exercise energy expenditure (EEE) was deducted from energy intake (EI), and the remnant energy normalized to fat free mass (FFM) to determine energy availability (EA). Weight of all food and liquid consumed during three consecutive days determined EI. EEE was determined after isolating and deducting energy expended in exercise or physical activity above lifestyle from the total energy expenditure output as measured by Actigraph GT3X+. Dual energy x-ray absorptiometry (DXA) determined both FFM and BMD. Menstrual function was determined from a daily temperature-menstrual log kept by each participant for nine continuous months. Low EA (<45 kcal/kgFFM.d-1) was evident in 61.53% of the participants (athletes: 28.07 ±11.45 kcal/kgFFM.d-1, non-athletes: 56.97 ±21.38 kcal/kgFFM.d-1). The overall 36% MD seen among all participants was distributed as 40% among the athletes, and 29% among non-athletes. None of the athletes was amenorrheic. Low BMD was seen in 79% of the participants (athletes: 76%, non-athletes:86%). Overall, 10% of the participants (athletes: 4, non-athletes: 0) showed simultaneous presence of all three components of the TRIAD. The Independent sample t-test showed significant difference (t=5.860; p< 0.001) in prevalence of the TRIAD between athletes and non-athletes. The hypothesized higher prevalence of the TRIAD among athletes compared to non-athletes was partially accepted. To alleviate conditions arising from low EA, both athletes and their coaches need regular education on how to ensure they adequately meet specific dietary and nutritional requirements for their competition events

Association between energy availability and menstrual function in elite Kenyan runners

Low energy availability (EA) has been recognized as an instigator of menstrual dysfunction and subsequent hypoestrogenism that leads to deterioration in bone health. Elite Kenyan male athletes have been reported to often function under low energy balance. Therefore, the purpose of this study was to determine EA and menstrual function (MF) among elite Kenyan female athletes; and to explore the association between EA and MF in the athletes. The data were collected from 25 elite Kenyan runners and 14 non-athletes. Energy intake (EI) minus exercise energy expenditure (EEE) normalized to fat free mass (FFM) determined EA. EI was determined through weight of all food and liquid consumed over three consecutive days. EEE was determined after isolating and deducting energy expended in exercise or physical activity above lifestyle level from the total energy expenditure output as measured by Actigraph GT3X+. FFM was assessed using DXA. A daily temperature-menstrual log kept for nine continuous months was used to establish menstrual function. Overall, EA below 45 kcal/kgFFM.d-1 was seen in 61.53% of the participants (athletes: 28.07 ±11.45 kcal/kgFFM.d-1, non-athletes:56.97 ±21.38 kcal/kgFFM.d-1). Results on menstrual dysfunction were as follows: oligomenorrhea (athletes: 40%; non-athletes: 14.3%) and amenorrhea (non-athletes: 14.3%). None of the athletes were amenorrheic. Results did not show any significant association between EA and MF, but the low to sub-optimal EA among elite Kenyan female athletes raises concern for their future menstrual and bone health. . Educating the athletes and coaches will enhance achievement of the specific dietary and nutritional needs appropriate to their competition events

Structural vascular disease in Africans: Performance of ethnic-specific waist circumference cut points using logistic regression and neural network analyses: The SABPA study.

A recently proposed model for waist circumference cut points (RPWC), driven by increased blood pressure, was demonstrated in an African population. We therefore aimed to validate the RPWC by comparing the RPWC and the Joint Statement Consensus (JSC) models via Logistic Regression (LR) and Neural Networks (NN) analyses. Urban African gender groups (N=171) were stratified according to the JSC and RPWC cut point models. Ultrasound carotid intima media thickness (CIMT), blood pressure (BP) and fasting bloods (glucose, high density lipoprotein (HDL) and triglycerides) were obtained in a well-controlled setting. The RPWC male model (LR ROC AUC: 0.71, NN ROC AUC: 0.71) was practically equal to the JSC model (LR ROC AUC: 0.71, NN ROC AUC: 0.69) to predict structural vascular -disease. Similarly, the female RPWC model (LR ROC AUC: 0.84, NN ROC AUC: 0.82) and JSC model (LR ROC AUC: 0.82, NN ROC AUC: 0.81) equally predicted CIMT as surrogate marker for structural vascular disease. Odds ratios supported validity where prediction of CIMT revealed -clinical -significance, well over 1, for both the JSC and RPWC models in African males and females (OR 3.75-13.98). In conclusion, the proposed RPWC model was substantially validated utilizing linear and non-linear analyses. We therefore propose ethnic-specific WC cut points (African males, ≥90 cm; -females, ≥98 cm) to predict a surrogate marker for structural vascular disease.

Determining cut-off values for neck circumference as a measure of the metabolic syndrome amongst a South African cohort: the SABPA study.

The aim was to determine receiver operating characteristic (ROC) neck circumference (NC) cut offs best associated with the metabolic syndrome (MetS) in a South African cohort. We included 409 urban Africans and Caucasians and stratified them into gender and age groups (25-45 years; 45-65 years). Measurements included anthropometric, fasting overnight urine and biological markers for the MetS (systolic and diastolic blood pressure, glucose, triglycerides, and high density lipoprotein). ROC analysis determined pathological (NC) cut-points of 39 and 35 cm for young and older African men; 32 and 35 cm for young and old African women; 40 and 41 cm for Caucasian men; 34 and 33 cm for Caucasian women. Pathological NC cut-points significantly predicted MetS in all ethnic-gender-age groups except in African women (ORs 2.3-5.4; 95% CI 1.36-16.5). Multiple regression analyses revealed that MetS prevalence and ROC cut-points were not associated with renal impairment in any groups. ROC NC cut-points demonstrated that NC may be used as an additional anthropometric marker to predict the MetS in a South African cohort but not in African women.

Determining the waist circumference cut off which best predicts the metabolic syndrome components in urban Africans: the SABPA study.

Various studies have shown that the relationship between waist circumference (WC) and abdominal obesity is age, gender as well as ethnicity-dependent. WC criteria for Sub Saharan Africans have not been defined by the International Diabetes Federation (IDF). The aim was to determine which WC cut off best predicted Metabolic Syndrome (MetS) in a group of urban African teachers (80 males and 93 females). We determined sphygmomanometer blood pressure, WC, glucose, high density lipoprotein cholesterol (HdL) and triglyceride (TRIG) values. The males' MetS profile was less favourable as their glucose, TRIG and blood pressure levels were higher than the proposed cut off for MetS. The females could be classified as obese, based on their mean BMI (32.78±6.36) and WC (93.48±15.68). Receiver operating characteristic (ROC) WC cut offs of 90, 91, 94 and 96 cm for the respective MetS components in males (blood pressure, HdL, glucose and TRIG) were suggested. In the females, cut offs of 92, 98, 94 and 94 cm for TRIG, blood pressure, HdL and glucose respectively, were put forward. Odds ratios revealed that increased blood pressure best predicted ROC WC in both males (OR 9.59; 95% CI 3.14-29.32) and females (OR 3.11; 95% CI 1.30-7.42) irrespective of age. We suggest that the optimal cut off point for the males be set at 90 cm, as opposed to the current 94 cm; whilst the female cut off be set at 98 cm as opposed to the existing cut off of 80 cm. Larger sample groups are recommended to justify our data.

The sensitivity of waist-to-height ratio in identifying children with high blood pressure.

We determined the sensitivity of waist-to-height ratio (WHtR) as a marker for high blood pressure in children aged nine to 15 years (n = 1 131), from schools in the North West province, South Africa. Anthropometric and blood pressure measurements were taken. The sensitivity and specificity of the WHtR to identify children with high blood pressure were evaluated. At a cut-off value of 0.5, 7.9% of the girls and 3.4% of the boys had central adiposity. Thirteen per cent of the children were hypertensive. The optimal WHtR cut-off value to identify children with hypertension was 0.41 in both boys and girls. Positive correlations were observed between anthropometric indices. Using linear regression analyses, age and body mass index were significant predictors of high blood pressure in boys, while for girls it was height and weight. Results suggest that adopting a WHtR cut-off value < 0.5 could enhance the use of WHtR as a marker for high blood pressure in children.

The association between anthropometric parameters, the metabolic syndrome and microalbuminuria in black Africans: the SABPA study.

We aimed to determine which surface anthropometric and metabolic syndrome (MS) markers could be associated with the development of microalbuminuria (MA), and assessed 200 urban Africans (25-60 years) stratified into low (< or = 0.90 and < or = 0.85) and high ( > 0.90 and > 0.85) waist-tohip ratio (WHR) groups from the North-West province. Anthropometric and fasting MS markers, such as systolic and diastolic blood pressure (BP), and glucose, triglyceride (TG) and high-density lipoprotein (HDL) levels, as well as MA markers were measured. Males revealed higher lifestyle risk factors (body mass index, smoking, alcohol consumption, low physical activity), anthropometric and MS markers compared to the females. The same overall trend was seen for high-WHR males but not for high-WHR females compared to their low-WHR counterparts. Both high-WHR groups revealed increased glucose values (males, 6.34 mmol/l; females, 6.13 mmol/l). Multiple linear regression analysis, independent of confounders, showed positive associations between diastolic blood pressure (DBP) (high WHR and all males), TG, waist circumference (WC) and development of MA in all males. In high-WHR females, positive associations existed only between WC and the development of MA, while neck circumference (NC) was associated with MA development in all females. To conclude, vascular BP, TG and WC were associated with risk of renal impairment in males, while in females, NC and WC circumferences were associated with this risk.

Should obesity be blamed for the high prevalence rates of hypertension in black South African women?

Hypertension is highly prevalent in South Africa, resulting in high stroke mortality rates. Since obesity is very common among South African women, it is likely that obesity contributes to the hypertension prevalence. The aims were to determine whether black African women have higher blood pressures (BPs) than Caucasian women, and whether obesity is related to their cardiovascular risk. African (N=102) and Caucasian (N=115) women, matched for age and body mass index, were included. Correlations between obesity (total body fat, abdominal obesity and peripheral fat) and cardiovascular risk markers (haemodynamic parameters, lipids, inflammatory markers, prothrombotic factors, adipokines, HOMA-IR (homoeostasis model assessment insulin resistance)) were compared between the ethnic groups (adjusted for age, smoking, alcohol and physical activity). Comparisons between low- and high-BP groups were also made for each ethnic group. Results showed that African women had higher BP (P<0.01) with increased peripheral vascular resistance. Surprisingly, African women showed significantly weaker correlations between obesity measures and cardiovascular risk markers when compared to Caucasian women (specifically systolic BP, arterial resistance, cardiac output, fibrinogen, plasminogen activator inhibitor-1, leptin and resistin). Interestingly, the latter risk markers were also not significantly different between low- and high-BP African groups. African women, however, presented significant correlations of obesity with triglycerides, C-reactive protein and HOMA that were comparable to the Caucasian women. Although urban African women have higher BP than Caucasians, their obesity levels are weakly related to traditional cardiovascular risk factors compared to Caucasian women. The results, however, suggest a link with the development of insulin resistance.

Dietary markers of hypertension associated with pulse pressure and arterial compliance in black South African children: the THUSA Bana Study.

AIM: The aim of the study was to determine which dietary factors contribute to the impairment of arterial compliance, stroke volume, total peripheral resistance and pulse pressure, and could thereby be identified as risk markers in the development of hypertension in black children. METHODS: Children aged 10 to 15 years were recruited from 30 schools in the North West Province over two years (2000 to 2001). These children comprised 321 black males and 373 females from rural to urbanised communities and 40 male and 79 females subjects with identified high-normal to hypertensive blood pressure. Blood pressure was measured by means of a Finapres apparatus. Through analysis with the Fast Modelflo software program, systemic arterial compliance, pulse pressure, total peripheral resistance and stroke volume were obtained. A 24-hour dietary recall questionnaire and weight and height measurements were taken. RESULTS: In a stepwise regression analysis the following nutrient were significantly associated (p < or = 0.05) with cardiovascular parmeters of hypertensive subjects: protein, carbohydrates, total fat, polyunsaturated fat, mono-unsaturated fat, saturated fat, fibre, vitamin A, nicotinic acid, biotin, vitamin B(12), ascorbic acid, vitamin E, magnesium, manganese, phoshorus and iron. No significant dietary markers were indicated for the normotensive groups. Dietary intakes of most of these nutrients were below the dietary reference intakes for all groups. CONCLUSIONS: The results indicate strong associations of protein, polyunsaturated fats, fibre, vitamin A, vitamin C, vitamin E, nicotinic acid, vitamin B(12), biotin and phosphorus with the rate of hypertension in black South African children.

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.

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 < or = 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.

Impact of urbanisation on serum lipid profiles--the THUSA survey.

OBJECTIVE: To examine the impact of urbanisation on lipid profiles of black South Africans, stratified for HIV status. DESIGN: Cross-sectional population-based survey. SETTING: North West province of South Africa. SUBJECTS: A representative sample of 1,854 apparently healthy volunteers aged > or = 15 years, was recruited from 37 randomly selected sites throughout the province. Subjects were stratified into five urbanisation strata (S): S1 rural villages, S2 farms, S3 informal housing or 'squatter camps' S4 urban townships, and S5 surburban housing. OUTCOME MEASURES: Demographic, physical activity and dietary intake information was collected using validated and culture-sensitive questionnaires. Anthropometric measurements and lipid analyses were determined using standardised methodology. RESULTS: The results revealed significantly lower mean (95% confidence interval) total serum cholesterol (TC) levels in HIV-negative men in S1-S4 compared with S5 (S1 3.91 (3.77-4.05) v. S5 4.79 (4.54-5.04) mmol/l). In HIV-negative women, TC levels were significantly lower in S1-S3 than in S4 and S5 (S1 4.05 (3.94-4.17) v. S5 4.79 (4.59-5.00) mmol/l). The same trends were seen for serum low-density lipoprotein cholesterol (LDLC) and triglycerides and in HIV-positive subjects. Binary logistical analysis indicated that the main factor responsible for the increased TC levels seemed to be increased body mass index (BMI) due to decreased physical activity. CONCLUSIONS: Serum lipid levels increased with urbanisation although they remained within levels recommended for other populations. This may, however, become an important health problem in future if preventive strategies are not implemented. Culturally sensitive physical activity programmes to decrease BMI, targeted at professional men and women, and women in urban townships, seem to constitute the most appropriate intervention.

Stability of somatotypes in 4 to 10 year-old rural South African girls.

In 1996, a mixed Ellisras longitudinal study (ELS) was initiated to assess the stability of somatotypes in 408 girls who comprised 99 pre-school and 309 primary school children in Ellisras rural area in the Northern Province of South Africa. The children's somatotype was assessed using the Heath-Carter anthropometric method. Anthropometric dimensions were taken according to the protocol of the International Society for the Advancement of Kinanthropometry (ISAK). The most stable pre-school and primary school girl had migratory distances (MDs) of 2.6 and 3.4, respectively, while the least stable pre-school and primary school girl had MDs of 17.9 and 24.4, respectively. The mean somatotype of the pre-school children was mesomorph-ectomorph throughout the complete age range, while the mean somatotype of primary school girls was mesomorph-ectomorph for all the age groups except for the 9.5 years group at which it was in the balanced ectomorph. The inter-age partial correlations for endomorphy and ectomorphy were high and significant, but insignificant with regard to mesomorphy.

Soluble-fibre concentrate lowers plasminogen activator inhibitor-1 in baboons (Papio ursinus).

The effects of a soluble NSP (fibre) concentrate (SFC) on plasma fibrinogen and plasminogen activator inhibitor-1 (PAI-1), serum and liver lipids and lipoproteins and glucose tolerance were compared with those of bezafibrate (BF), a lipid-lowering drug, in obese baboons (Papio ursinus). The basal diet was a high-fat (37% of total energy), low-NSP (12.4 g/d) Westernized diet, supplemented for 8 weeks with either 20 SFCg/baboon per d or 6.7 mg BF/kg body weight per baboon per d. SFC supplementation significantly lowered PAI-1, total serum cholesterol, HDL-cholesterol and circulating free fatty acid levels. BF significantly lowered total serum cholesterol, but unexpectedly raised serum triacylglycerol levels. Although not statistically significant, the mean liver triacylglycerol concentration of baboons fed on BP was lower than that of baboons fed on SFC supplements. These results suggest that: (1) the mechanism of action of the two cholesterol-lowering treatments differ, with BF having a liver triacylglycerol-lowering effect and (2) the SFC ahd additional beneficial effect on fibrinolysis by lowering PAI-1 levels.

Preliminary clinical trial with a new hypotensive, guanabenz, in a group of hypertensive patients.

In a small preliminary clinical trial of guanabenz in 16 hypertensives also under treatment with diuretics (hydrochlorothiazide and amiloride), blood pressure was safely and completely controlled in 10 (64%), the criterion for "control" being a reduction to the strict level specified by the Society of Actuaries (130/85 m lambda Hg). The dosage of guanabenz was adjusted upward from 16 mg/day until blood pressure normalized or side effects intervened. The 16 patients accumulated 97 months of guanabenz treatment. The 6 unsuccessful cases included only 2 outright therapeutic failures; the other 4 patients discontinued treatment for various reasons: dry mouth and nausea (with good blood pressure reduction); aggravation of existing depression; or generalized urticaria. The fourth patient discontinued for reasons unknown.