Deriving an optimal threshold of waist circumference for detecting cardiometabolic risk in sub-Saharan Africa.

BACKGROUND: Waist circumference (WC) thresholds derived from western populations continue to be used in sub-Saharan Africa (SSA) despite increasing evidence of ethnic variation in the association between adiposity and cardiometabolic disease and availability of data from African populations. We aimed to derive a SSA-specific optimal WC cut-point for identifying individuals at increased cardiometabolic risk. METHODS: We used individual level cross-sectional data on 24 181 participants aged ⩾15 years from 17 studies conducted between 1990 and 2014 in eight countries in SSA. Receiver operating characteristic curves were used to derive optimal WC cut-points for detecting the presence of at least two components of metabolic syndrome (MS), excluding WC. RESULTS: The optimal WC cut-point was 81.2 cm (95% CI 78.5-83.8 cm) and 81.0 cm (95% CI 79.2-82.8 cm) for men and women, respectively, with comparable accuracy in men and women. Sensitivity was higher in women (64%, 95% CI 63-65) than in men (53%, 95% CI 51-55), and increased with the prevalence of obesity. Having WC above the derived cut-point was associated with a twofold probability of having at least two components of MS (age-adjusted odds ratio 2.6, 95% CI 2.4-2.9, for men and 2.2, 95% CI 2.0-2.3, for women). CONCLUSION: The optimal WC cut-point for identifying men at increased cardiometabolic risk is lower (⩾81.2 cm) than current guidelines (⩾94.0 cm) recommend, and similar to that in women in SSA. Prospective studies are needed to confirm these cut-points based on cardiometabolic outcomes.International Journal of Obesity advance online publication, 31 October 2017; doi:10.1038/ijo.2017.240.

Psychosocial factors and obesity in 17 high-, middle- and low-income countries: the Prospective Urban Rural Epidemiologic study.

BACKGROUND/OBJECTIVES: Psychosocial stress has been proposed to contribute to obesity, particularly abdominal, or central obesity, through chronic activation of the neuroendocrine systems. However, these putative relationships are complex and dependent on country and cultural context. We investigated the association between psychosocial factors and general and abdominal obesity in the Prospective Urban Rural Epidemiologic study. SUBJECTS/METHODS: This observational, cross-sectional study enrolled 151 966 individuals aged 35-70 years from 628 urban and rural communities in 17 high-, middle- and low-income countries. Data were collected for 125 290 individuals regarding education, anthropometrics, hypertension/diabetes, tobacco/alcohol use, diet and psychosocial factors (self-perceived stress and depression). RESULTS: After standardization for age, sex, country income and urban/rural location, the proportion with obesity (body mass index ≥30 kg m(-)(2)) increased from 15.7% in 40 831 individuals with no stress to 20.5% in 7720 individuals with permanent stress, with corresponding proportions for ethnicity- and sex-specific central obesity of 48.6% and 53.5%, respectively (P<0.0001 for both). Associations between stress and hypertension/diabetes tended to be inverse. Estimating the total effect of permanent stress with age, sex, physical activity, education and region as confounders, no relationship between stress and obesity persisted (adjusted prevalence ratio (PR) for obesity 1.04 (95% confidence interval: 0.99-1.10)). There was no relationship between ethnicity- and sex-specific central obesity (adjusted PR 1.00 (0.97-1.02)). Stratification by region yielded inconsistent associations. Depression was weakly but independently linked to obesity (PR 1.08 (1.04-1.12)), and very marginally to abdominal obesity (PR 1.01 (1.00-1.03)). CONCLUSIONS: Although individuals with permanent stress tended to be slightly more obese, there was no overall independent effect and no evidence that abdominal obesity or its consequences (hypertension, diabetes) increased with higher levels of stress or depression. This study does not support a causal link between psychosocial factors and abdominal obesity.

Glucose tolerance study in low and normal birth weight young adults.

Objective: To determine blood glucose levels by conducting an oral glucose tolerance test in low and normal birth weight young black adults. Design: Acase control study was done. Seventy students in the College of Health Sciences who had neonatal clinic cards as proof of birth weight were recruited into the study. Blood glucose levels were measured before, during and after the oral glucose tolerance test. Setting: Department of Physiology, University of Zimbabwe, College of Health Sciences, Harare, Zimbabwe. Main Outcome Measures and Results: A total of 70 young adult participants, 47(67%) females and 23(33%)males with mean age 20.28±0.19 years were recruited. 30 had Low Birth Weight (LBW, 21 females and 9 males) and 40 had Normal Birth Weight (NBW,26 females and 14 males).LBW individuals had significantly elevated (p<0.05) mean blood glucose levels at 30minutes(9.41±0.91 for LBW and 7.24±0.28 for NBW, p=0.029) and 60 minutes (9.22±0.75 for LBW and 7.57±0.36 for NBW, p=0.035) after the oral glucose tolerance test. Oral glucose tolerance testing detected 1case of type II diabetes (LBW individual), 13cases of impaired glucose tolerance (9 LBW and 4 NBW individuals)and 1 case of impaired fasting glucose (LBW individual).LBW was associated with an odds ratio of 3.1 for impaired glucose tolerance and it was statistically significant, p<0.05 (p=0.027). Conclusion: Low birth weight was associated with glucose intolerance and significantly higher mean blood glucose levels at 30 and 60 minutes after glucose loading in young adults.

Aspects of insulin resistance in urbanisation-related hypertension in Zimbabwe: a preliminary report.

Insulin resistance has been associated with essential hypertension, obesity and old age. Likewise high blood pressure has been observed to develop in some rural people who migrate to urban areas in developing countries like Zimbabwe. The pathogenesis of this urbanisation-related hypertension is still unknown. We therefore investigated aspects of insulin resistance in urbanisation-related hypertension in Zimbabwean blacks using oral glucose tolerance tests. Thirty normotensive subjects and 30 newly diagnosed hypertensive patients participated in this study. All subjects had blood pressures measured by random zero sphygmomanometry. Fasting blood samples were taken before a 75 g oral glucose load was given. Four other blood samples were subsequently collected at 30 minute intervals and determination of blood glucose and insulin levels was made. Fasting glucose (mmol/l) and fasting insulin (in microU/ml) levels were, respectively, 4.8 +/- 0.2 and 19 +/- 2 in hypertensive patients which were significantly higher than 4.0 +/- 0.2 and 13 +/- 1.6 in normotensive patients (P < 0.05). In addition the area under the insulin curve was significantly higher in hypertensive than in normotensive patients (P < 0.05). These findings suggest that insulin resistance may play a role in urbanisation-related hypertension.

Correlates of blood pressure in an urban Zimbabwean population and comparison to other populations of African origin.

We have evaluated the relationship between systolic blood pressure (SBP) and age, body mass index (BMI), waist circumference, sodium to potassium ratio (Na/K), and tobacco use in an urban African population. We conducted a random, population-based, cross-sectional survey of people 25 years and older in Marondera, Zimbabwe, with over-sampling in older age groups (n = 775), using a method comparable to that used in International Collaborative Study on Hypertension in Blacks (ICSHIB). The age-adjusted prevalences of hypertension in Marondera (SBP >/=140/DBP >/=90/antihypertensive medication) were 30% for women and 21% for men. The average BMI was 26.3 kg/m2 for women and 21.4 kg/m2 for men. The prevalence of hypertension had a steep association with age and in women ranged from 15% (25-34 years) to 63% (55 years and over) and in men from 9% to 47%. No tobacco use in women and greater Na/K ratio in spot urines in men were significantly associated with an increased SBP. In both men and women the levels of hypertension and SBP were strongly positively associated with BMI, although the relationship appeared to plateau in women with a BMI greater than >/=25 kg/m2. At a given BMI, men and women had similar SBPs and prevalences of hypertension. There is a very high prevalence of hypertension among urban Zimbabweans, particularly among women. Under the assumption the studies are comparable, the prevalence of hypertension in Zimbabwean women (41%) and men (26%) after age adjustment to the ICSHIB populations, appeared higher than almost all of the ICSHIB populations, including those with higher average body mass indexes. Journal of Human Hypertension (2000) 14, 65-73.

Microalbuminuria in urban Zimbabwean women.

The prevalence of microalbuminuria (MAU) in African populations has not been reported, nor has the relationship between MAU and hypertension been reported for these populations. We collected spot urine samples from 370 women, 25 years and older as a part of a population-based, cross-sectional blood pressure survey in an urban community in Zimbabwe and analysed the samples for albumin and beta2-microglobulin. The age-adjusted prevalence of hypertension was 30% for women 25 years and older in this community. After excluding the samples with hematuria (11%), the prevalence of MAU (3.0 < or = albumin-to-creatinine ratio (ACR, mg/mmol) <25.0) in the study population was 9%. When age-adjusted to the population in the community, the prevalence was 8% among women 25 years and older. The prevalence of MAU was substantially higher in hypertensive (HT) than in normotensive (NT) women (16% vs 4%, P<0.001). A significantly higher level of log ACR in HT was found in each age group except the youngest age group (age 25-34). In age-adjusted multiple regression, percent fat mass was negatively associated with log ACR (beta = -1. 18, 95% CI (-0.23, -2.21), P = 0.02). In a similar regression analysis, higher log beta8-microglobulin-to-creatinine ratio was very strongly associated with higher log ACR (beta = 0.34, 95% CI (0.25, 0.43), P<0.0001) and significantly associated with lower percent fat mass (beta = -1.02, 95% CI (-0.25, -1.8), P = 0.01). These results suggest that MAU is frequently caused by hypertension, but that other diseases may contribute to its presence.

Effect of variation in environmental temperature on blood pressure: is it important?

OBJECTIVES: To study the effect of variation in environmental temperature on blood pressure and pulse. DESIGN: Repeated blood pressure and pulse measurements in volunteers on two days when environmental temperatures differed by 10 degrees C. SETTING: Part of an ongoing community based study. SUBJECTS: 25 Black subjects (23 males and two females) volunteered from a population cohort participating in an ongoing longitudinal study examining cardiovascular risk factors in an urban African Black environment. MAIN OUTCOME MEASURE: Mean systolic and diastolic blood pressures and pulse rates. RESULTS: The systolic and diastolic blood pressures were significantly higher when recorded at 15 degrees C than at 25 degrees C, mean difference 32.2 +/- 4.2, p < 0.001 and 19.5 +/- 3.0 p < 0.001) for systolic and diastolic blood pressures respectively. The pulse rate per minute at 15 degrees C was significantly lower than at 25 degrees C (mean difference 11.1 +/- 3.2 p = 0.002). CONCLUSIONS: A decrease in environmental temperature by 10 degrees C appears to increase blood pressure. Awareness of this phenomenon is important, especially when surprisingly high blood pressures are observed during low ambient temperatures, to avoid over diagnosis of hypertension. This phenomenon, together with that already established of the white coat hypertension, may lead to the erroneous diagnosis of hypertension.

Comparison of the Omron HEM-713C automated blood pressure monitor with a standard ausculatory method using a mercury manometer.

OBJECTIVES: To compare the Omron HEM-713C automated blood pressure machine with the standard ausculatory method using a mercury manometer. DESIGN: Blood pressures of randomly selected subjects were measured using both the Omron HEM-713C and the mercury manometer. SETTING: Dombotombo surburb in Marondera, Zimbabwe. SUBJECTS: One hundred and sixteen subjects 25 years and above (47 males and 69 females) randomly selected in Marondera. MAIN OUTCOME MEASURE: Systolic blood pressure and diastolic blood pressure. RESULTS: The Omron HEM-713C passed with a grade B for both systolic and diastolic blood pressures when using the British Hypertension Society protocol. It also passed both systolic and diastolic criteria for Association of the Advancement of Medical Instrumentation. CONCLUSION: The Omron HEM-713C compares well with the standard mercury manometer, we therefore recommend its use in both research and clinical applications which require blood pressure measurements.

The nutritional intake of undergraduates at the University of Zimbabwe College of Health Sciences.

In developing countries the cost of treating disease is much more than prevention and so there is now a lot of interest in understanding nutrition. In this pilot study we selected a cohort of pre-clinical students studying at the College of Health Sciences in the University of Zimbabwe. This study was carried to investigate the gender-based weekly consumption of different food categories amongst University of Zimbabwe students. Semi-structured questionnaires distributed to 100 undergraduate students (male= 47; female= 52). The proportion of male and female respondents, age and body weight did not differ significantly. Principal foods consumed by males included sadza and cerevita; naartjies, bananas and avocado pears; tomatoes, onions, covo and spinach; beef; and condensed milk and powdered milk occupied the larger proportions. Females frequently ate a lot of bread, cerevita, sadza and cereal; lemons and avocado pears; onions, tomatoes, rape and covo; beef and soya meat; creamer, powdered milk and milk. This study suggests that females consumed a greater variety of food, including the infrequent types by comparison with men.

Pathophysiological mechanisms of urbanisation-related hypertension and the sodium pressor response in black Zimbabweans.

This study examined the role of endothelin (ET), the thromboxane A2 (TXA2)-prostacyclin (PGI2) ratio (TXA2/PGI2), plasma renin activity (PRA) and urinary aldosterone excretion (ALDO) in urban hypertensive patients and in the sodium pressor response in normotensives. Twenty-seven urban hypertensive patients and the same number of normotensive controls were studied on baseline diet, after 5 days of sodium restriction and after 5 days of sodium loading. Mean arterial blood pressure, plasma and ET values, PRA, TXA2/PGI2 and ALDO were assessed on each diet. The results showed that baseline PRA was suppressed in the hypertensive patients; this indicates that urbanisation-related hypertension is of the low renin type. ET levels and TXA2/PGI2 were higher in hypertensive than in normotensive subjects, suggesting an association between high blood pressure and these factors. Although the baseline PRA in hypertensives was suppressed, urinary ALDO was no different from that in the normotensive controls where PRA was normal. In addition, sodium restriction did not increase PRA in hypertensive subjects while it more than doubled it in the controls. However, ALDO in hypertensive patients increased to levels that were no different from those in the normotensive subjects. Sodium loading increased blood pressure, ET values and TXA2/PGI2 indicating an association between the latter two factors and the sodium pressor response in those with hypertension. ALDO decreased to similar levels on sodium loading in the two groups. This decrease in ALDO was accompanied by suppression of PRA only in normotensive subjects. In conclusion, the low-renin-activity urban hypertensives we studied had increased baseline ET levels and TXA2/PGI2.(ABSTRACT TRUNCATED AT 250 WORDS)

Salt sensitivity is not associated with hyperinsulinaemia in a sample of rural black Zimbabweans.

OBJECTIVES: To investigate the relationship between salt sensitivity and hyperinsulinaemia in rural black African subjects. DESIGN: An intervention study where 27 subjects were divided into two groups; group 1 was initially salt loaded (300 mmol Na+/day), while group 2 was salt restricted (25 mmol Na+/day), each for 4 days, after which a cross-over study was done. SETTING: Chidamoyo, a rural area 383 km north of Harare, Zimbabwe. SUBJECTS: Twenty-seven rural volunteers (16 women, 11 men). OUTCOME MEASURES: Systolic and diastolic blood pressures, salt sensitivity, insulin and glucose levels, body mass index and mean arterial pressure. RESULTS: Mean arterial pressure, which was 91 +/- 2 mmHg on a low-salt diet, increased significantly (P < 0.01) to 105 +/- 3 mmHg on high-salt diet in the salt-sensitive subjects. In the same salt-sensitive subjects, the fasting insulin level was 8.4 +/- 0.8 microU/ml on a low-salt and 6.1 +/- 1.0 microU/ml on a high-salt diet. The difference was not statistically significant. CONCLUSIONS: Although salt pressor sensitivity was demonstrated in the subjects, there was no accompanying increase but rather a decrease in fasting insulin levels, suggesting that in the short term, salt sensitivity and hyperinsulinaemia are not linked in raising blood pressure in this sample of rural Zimbabwean subjects.