Do current guidelines for waist circumference apply to black Africans? Prediction of insulin resistance by waist circumference among Africans living in America

Waist circumference and cardiometabolic parameters in people of African/Caribbean ancestry with HIV in South London (CKD-AFRICA study)

BACKGROUND

There are no validated waist circumference (WC) cut-offs to define metabolic syndrome in Black people with HIV.

METHODS

Cross-sectional analyses within the CKD-AFRICA study. We used Pearson correlation coefficients and receiver operating characteristic (ROC) curves to describe the relationship between WC and cardiometabolic parameters including triglycerides, cholesterol, glucose, glycated haemoglobin (HbA1c), and homeostatic model assessment for insulin resistance (HOMA-IR), and to identify optimal WC cut-offs for each of these outcomes.

RESULTS

We included 383 participants (55% female, median age 52 years) with generally well controlled HIV. Female and male participants had similar WC (median 98 vs. 97 cm, p = .16). Generally weak correlations (r2 < 0.2) between WC and other cardiometabolic parameters were observed, with low (<0.7) areas under the ROC curves. The optimal WC cut-offs for constituents of the metabolic syndrome, HbA1c and HOMA-IR ranged from 92 to 101 cm in women and 89-98 cm in men, respectively; these cut-offs had variable sensitivity (52%-100%) and generally poor specificity (28%-72%).

CONCLUSIONS

In this cohort of Black people with HIV, WC cut-offs for cardiometabolic risk factors in male participants were in line with the recommended value of 94 cm while in female participants they vastly exceeded the recommended 80 cm for white women.

Waist circumference and glycaemia are strong predictors of progression to diabetes in individuals with prediabetes in sub-Saharan Africa: 4-year prospective cohort study in Malawi

Sub-Saharan Africa is projected to have the highest increase in the number of people with diabetes worldwide. However, the drivers of diabetes in this region have not been clearly elucidated. The aim of this study was to evaluate the incidence of diabetes and the predictors of progression in a population-based cohort with impaired fasting glucose (IFG) in Malawi. We used data from an extensive rural and urban non-communicable disease survey. One hundred seventy-five, of 389 individuals with impaired fasting glucose (IFG) at baseline, age 48 ±15 years and body mass index 27.5 ±5.9 kg/m2 were followed up for a median of 4.2 years (714 person-years). Incidence rates were calculated, and predictors of progression to diabetes were analysed using multivariable logistic regression models, with overall performance determined using receiver operator characteristics (ROC) curves. The median follow-up was 4.2 (IQR 3.4-4.7) years. Forty-five out of 175 (26%) progressed to diabetes. Incidence rates of diabetes were 62.9 per 1000 person-years 95% CI, 47.0-84.3. The predictors of progression were higher; age (odds ratio [OR] 1.48, P = 0.046), BMI (OR 1.98, P = 0.001), waist circumference (OR 2.50,P<0.001), waist-hip ratio (OR 1.40, P = 0.03), systolic blood pressure (OR 1.56, P = 0.01), fasting plasma glucose (OR 1.53, P = 0.01), cholesterol (OR 1.44, P = 0.05) and low-density lipoprotein cholesterol (OR 1.80, P = 0.002). A simple model combining fasting plasma glucose and waist circumference was predictive of progression to diabetes (ROC area under the curve = 0.79). The incidence of diabetes in people with IFG is high in Malawi and predictors of progression are like those seen in other populations. Our data also suggests that a simple chart with probabilities of progression to diabetes based on waist circumference and fasting plasma glucose could be used to identify those at risk of progression in clinical settings in sub-Saharan Africa.

Fructosamine is Not a Reliable Test for the Detection of Hyperglycemia: Insight from the Africans in America Study

Objective

To improve detection of abnormal glucose tolerance (Abnl-GT), attention has moved beyond the oral glucose tolerance test (OGTT), to non-fasting markers of glycemia, specifically, HbA1c, fructosamine (FA) and glycated albumin (GA). Emerging data suggest that in African descent populations, the combination of HbA1c and GA is superior to the combination of HbA1c and FA. However, the diagnosis of Abnl-GT is usually based on tests which are performed only once. As reproducibility of Abnl-GT diagnosis by HbA1c, fructosamine (FA) and glycated albumin (GA) is unknown, reproducibility of Abnl-GT diagnosis by HbA1c, FA and GA were assessed in 209 African-born Blacks living in America.

Methods

At Visits 1 and 2 (9 ± 4 days apart), samples were obtained for HbA1c, FA and GA levels. Glucose tolerance status was determined at Visit 1 by OGTT. Reproducibility was based on the К-statistic and paired t-tests. Thresholds for the diagnosis of Abnl-GT by FA and GA which corresponded to an HbA1c of 5.7% were 235umol/L and 14.6%, respectively.

Results

Abnl-GT occurred in 38% (80/209). Diagnostic reproducibility was excellent for HbA1c (К≥0.86) and GA (К≥0.89), but only moderate for FA (К=0.59). Neither HbA1c nor GA levels varied between visits (both P≥0.3). In contrast, FA was significantly lower at Visit 2 than Visit 1(P<0.01).

Conclusion

As HbA1c and GA provided similar diagnostic results on different days and FA did not, HbA1C and GA are superior to FA in both clinical care settings and epidemiologic studies.

Prevalence and characteristics of metabolic syndrome and its components among adults living with and without HIV in Nigeria: a single-center study

BACKGROUND

Persons living with HIV (PLHIV) now live longer due to effective combination antiretroviral therapy. However, emerging evidence indicates that they may be at increased risk for some cardiometabolic disorders. We compared the prevalence of metabolic syndrome (MetS) and its component disorders between persons living with and without HIV in Nigeria.

METHODS

This was a cross-sectional analysis of baseline data from a prospective cohort study of non-communicable diseases among PLHIV along with age- and sex-matched persons without HIV (PWoH) at the University of Abuja Teaching Hospital Nigeria. We collected sociodemographic and clinical data, including anthropometric measures and results of relevant laboratory tests. MetS was defined using a modification of the third report of the National Cholesterol Education Program Adult Treatment Panel (NCEP ATP III) criteria.

RESULTS

Of the 440 PLHIV and 232 PWoH, women constituted 50.5% and 51.3% respectively. The median age of the PLHIV was 45 years while that of the PWoH was 40 years. The prevalence of MetS was 30.7% (95% CI: 26.4%, 35.2%) and 22.8% (95% CI: 17.6%, 28.8%) among the PLHIV and PWoH respectively (P = 0.026). Independent associations were found for older age (P < 0.001), female sex (P < 0.001), family history of diabetes (P < 0.001), family history of hypertension (P = 0.013) and alcohol use (P = 0.015). The prevalence of component disorders for PLHIV versus PWoH were as follows: high blood pressure (22.3% vs 20.3%), prediabetes (33.8% vs 21.1%), diabetes (20.5% vs 8.2%), high triglycerides (24.5% vs 17.2%), low HDL-Cholesterol (51.1% vs 41.4%), and abdominal obesity (38.4% vs 37.1%). Adjusting for age and sex, prediabetes, diabetes, and low HDL-Cholesterol were significantly associated with HIV status. Duration on antiretroviral therapy, protease inhibitor-based regimen, CD4 count, and viral load were associated with some of the disorders mostly in unadjusted analyses.

CONCLUSION

We found a high burden of MetS and its component disorders, with significantly higher prevalence of dysglycemia and dyslipidemia among PLHIV as compared to PWoH. Integration of strategies for the prevention and management of MetS disorders is needed in HIV treatment settings.

The Africans in America study demonstrates that subclinical cardiovascular risk differs by etiology of abnormal glucose tolerance

Abnormal-glucose tolerance (Abnl-GT) is due to an imbalance between β-cell function and insulin resistance (IR) and is a major risk factor in cardiovascular disease (CVD). In sub-Saharan Africa, β-cell failure is emerging as an important cause of Abnl-GT (Abnl-GT-β-cell-failure). Visceral adipose tissue (VAT) volume and hyperlipidemia are major contributors to CVD risk when Abnl-GT is due to IR (Abnl-GT-IR). Yet, the CVD profile associated with Abnl-GT-β-cell failure is unknown. Therefore, our goals in 450 African-born Blacks (Male: 65%; Age: 39 ± 10 years; BMI 28 ± 5 kg/m²), living in America were to: (1) determine Abnl-GT prevalence and etiology; (2) assess by Abnl-GT etiology, associations between four understudied subclinical CVD risk factors in Africans: (a) subclinical myocardial damage (high-sensitivity troponin T (hs-cTnT)); (b) neurohormonal regulation (N-terminal pro-Brain-natriuretic peptide (NT-proBNP)); (c) coagulability (fibrinogen); (d) inflammation (high-sensitivity C-reactive protein (hsCRP)), as well as HbA_1c, Cholesterol/HDL ratio and VAT. Glucose tolerance status was determined by the OGTT. IR was defined by the threshold at the lowest quartile for the Matsuda Index (≤ 2.97). Abnl-GT-IR required both Abnl-GT and IR. Abnl-GT-β-cell-failure was defined as Abnl-GT without IR. VAT was assessed by CT-scan. For both the Abnl-GT-β-cell-failure and Abnl-GT-IR groups, four multiple regression models were performed for hs-cTnT; NT-proBNP; fibrinogen and hsCRP, as dependent variables, with the remaining three biomarkers and HbA_1c, Cholesterol/HDL and VAT as independent variables. Abnl-GT occurred in 38% (170/450). In the Abnl-GT group, β-cell failure occurred in 58% (98/170) and IR in 42% (72/170). VAT and Cholesterol/HDL were significantly lower in Abnl-GT-β-cell-failure group vs the Abnl-GT-IR group (both P < 0.001). In the Abnl-GT-β-cell-failure group: significant associations existed between hscTnT, fibrinogen, hs-CRP, and HbA_1c (all P < 0.05), and none with Cholesterol/HDL or VAT. In Abnl-GT-IR: hs-cTnT, fibrinogen and hsCRP significantly associated with Cholesterol/HDL (all P < 0.05) and NT-proBNP inversely related to fibrinogen, hsCRP, HbA_1c, Cholesterol/HDL, and VAT (all P < 0.05). The subclinical CVD risk profile differed between Abnl-GT-β-cell failure and Abnl-GT-IR. In Abnl-GT-β-cell failure subclinical CVD risk involved subclinical-myocardial damage, hypercoagulability and increased inflammation, but not hyperlipidemia or visceral adiposity. For Abnl-GT-IR, subclinical CVD risk related to subclinical myocardial damage, neurohormonal dysregulation, inflammation associated with hyperlipidemia and visceral adiposity. ClinicalTrials.gov Identifier: NCT00001853.

Non-invasive type 2 diabetes risk scores do not identify diabetes when the cause is β-cell failure: The Africans in America study

Background

Emerging data suggests that in sub-Saharan Africa β-cell-failure in the absence of obesity is a frequent cause of type 2 diabetes (diabetes). Traditional diabetes risk scores assume that obesity-linked insulin resistance is the primary cause of diabetes. Hence, it is unknown whether diabetes risk scores detect undiagnosed diabetes when the cause is β-cell-failure.

Aims

In 528 African-born Blacks living in the United States [age 38 ± 10 (Mean ± SE); 64% male; BMI 28 ± 5 kg/m²] we determined the: (1) prevalence of previously undiagnosed diabetes, (2) prevalence of diabetes due to β-cell-failure vs. insulin resistance; and (3) the ability of six diabetes risk scores [Cambridge, Finnish Diabetes Risk Score (FINDRISC), Kuwaiti, Omani, Rotterdam, and SUNSET] to detect previously undiagnosed diabetes due to either β-cell-failure or insulin resistance.

Methods

Diabetes was diagnosed by glucose criteria of the OGTT and/or HbA1c ≥ 6.5%. Insulin resistance was defined by the lowest quartile of the Matsuda index (≤ 2.04). Diabetes due to β-cell-failure required diagnosis of diabetes in the absence of insulin resistance. Demographics, body mass index (BMI), waist circumference, visceral adipose tissue (VAT), family medical history, smoking status, blood pressure, antihypertensive medication, and blood lipid profiles were obtained. Area under the Receiver Operator Characteristics Curve (AROC) estimated sensitivity and specificity of each continuous score. AROC criteria were: Outstanding: >0.90; Excellent: 0.80-0.89; Acceptable: 0.70-0.79; Poor: 0.50-0.69; and No Discrimination: 0.50.

Results

Prevalence of diabetes was 9% (46/528). Of the diabetes cases, β-cell-failure occurred in 43% (20/46) and insulin resistance in 57% (26/46). The β-cell-failure group had lower BMI (27 ± 4 vs. 31 ± 5 kg/m² P < 0.001), lower waist circumference (91 ± 10 vs. 101 ± 10cm P < 0.001) and lower VAT (119 ± 65 vs. 183 ± 63 cm³, P < 0.001). Scores had indiscriminate or poor detection of diabetes due to β-cell-failure (FINDRISC AROC = 0.49 to Cambridge AROC = 0.62). Scores showed poor to excellent detection of diabetes due to insulin resistance, (Cambridge AROC = 0.69, to Kuwaiti AROC = 0.81).

Conclusions

At a prevalence of 43%, β-cell-failure accounted for nearly half of the cases of diabetes. All six diabetes risk scores failed to detect previously undiagnosed diabetes due to β-cell-failure while effectively identifying diabetes when the etiology was insulin resistance. Diabetes risk scores which correctly classify diabetes due to β-cell-failure are urgently needed.

Black New Yorkers with Type 2 Diabetes: Afro-Caribbean Immigrants Have Lower BMI and Lower Waist Circumference than African Americans

OBJECTIVE

Using the 2013/2014 New York City (NYC) Health and Nutrition Examination Survey (NYCHANES) data, this exploratory study examined whether (a) type 2 diabetes (diabetes) prevalence differed between NYC Afro-Caribbeans and African Americans; (b) anthropometric, biochemical, and sociodemographic diabetes profiles differed between and within groups; and (c) diabetes odds differed between and within groups.

METHODS

Diabetes was defined as prior diagnosis, HbA1c ≥ 6.5% (7.8 mmol/L), or fasting glucose ≥ 126 mg/dL. Weighted logistic regression estimated diabetes odds by nativity and either waist circumference (WC) (cm) or BMI (kg/m²). All regression models controlled for age, hypertension, gender, education, income, marital status, physical activity, and smoking.

RESULTS

Among Afro-Caribbeans (n = 81, 65% female, age (mean ± SE) 49 ± 2 years, BMI 29.2 ± 0.7 kg/m²) and African Americans (n = 118, 50% female, age 47 ± 2 years, BMI 30.3 ± 0.9 kg/m²), Afro-Caribbeans with diabetes had lower BMI (29.9 ± 0.8 kg/m² vs. 34.6 ± 1.7 kg/m², P = 0.01) and lower WC (102 ± 2 cm vs. 114 ± 3 cm, P = 0.002) than African Americans with diabetes. Afro-Caribbeans with diabetes had lower prevalence of obesity (33.2% vs. 74.7%) and higher prevalence of overweight (57.2% vs. 13.5%) (P = 0.02) than African Americans with diabetes. Odds of diabetes did not differ between Afro-Caribbeans and African Americans. In models predicting the effect of WC, diabetes odds increased with WC (OR = 1.07 (95% CI 1.02, 1.11), P = 0.003) and age (OR = 1.09 (95% CI 1.03-1.15), P = 0.003) for African Americans only. In models predicting the effect of BMI, diabetes odds increased for Afro-Caribbeans with age (OR = 1.06 (1.01, 1.11)*, P = 0.04) and hypertension (OR = 5.62 (95% CI 1.04, 30.42), P = 0.045), whereas for African Americans, only age predicted higher diabetes odds (OR = 1.08 (95% CI 1.03, 1.14), P = 0.003).

CONCLUSIONS

In NYC, Afro-Caribbeans with diabetes have lower BMI and lower WC than African Americans with diabetes, but odds of diabetes do not differ. Combining African-descent populations into one group obscures clinical differences and generalizes diabetes risk.

Waist circumference thresholds predicting incident dysglycaemia and type 2 diabetes in Black African men and women

AIMS

To determine the waist circumference (WC) thresholds for the prediction of incident dysglycaemia and type 2 diabetes (T2D) in Black South African (SA) men and women and to compare these to the advocated International Diabetes Federation (IDF) Europid thresholds.

MATERIALS AND METHODS

In this prospective study, Black SA men (n = 502) and women (n = 527) from the Middle-aged Sowetan Cohort study who had normal or impaired fasting glucose at baseline (2011-2015) were followed up until 2017 to 2018. Baseline measurements included anthropometry, blood pressure and fasting glucose, HDL cholesterol and triglyceride concentrations. At follow-up, glucose tolerance was assessed using an oral glucose tolerance test. The Youden index was used to determine the optimal threshold of WC to predict incident dysglycaemia and T2D.

RESULTS

In men, the optimal WC threshold was 96.8 cm for both dysglycaemia and T2D (sensitivity: 56% and 70%; specificity: 74% and 70%, respectively), and had higher specificity (P < 0.001) than the IDF threshold of 94 cm. In women, the optimal WC threshold for incident dysglycaemia was 91.8 cm (sensitivity 86%, specificity 37%) and for T2D it was 95.8 cm (sensitivity 85%, specificity 45%), which had lower sensitivity, but higher specificity to predict incident dysglycaemia and T2D than the IDF threshold of 80 cm (sensitivity: 97% and 100%; specificity: 12% and 11%, respectively)).

CONCLUSIONS

We show for the first time using prospective cohort data from Africa that the IDF Europid WC thresholds are not appropriate for an African population, and show that African-specific WC thresholds perform better than the IDF Europid thresholds to predict incident dysglycaemia and T2D.

Obesity and the Bidirectional Risk of Cancer and Cardiovascular Diseases in African Americans: Disparity vs. Ancestry

Cardiovascular disease (CVD) and cancer often occur in the same individuals, in part due to the shared risk factors such as obesity. Obesity promotes adipose inflammation, which is pathogenically linked to both cardiovascular disease and cancer. Compared with Caucasians, the prevalence of obesity is significantly higher in African Americans (AA), who exhibit more pronounced inflammation and, in turn, suffer from a higher burden of CVD and cancer-related mortality. The mechanisms that underlie this association among obesity, inflammation, and the bidirectional risk of CVD and cancer, particularly in AA, remain to be determined. Socio-economic disparities such as lack of access to healthy and affordable food may promote obesity and exacerbate hypertension and other CVD risk factors in AA. In turn, the resulting pro-inflammatory milieu contributes to the higher burden of CVD and cancer in AA. Additionally, biological factors that regulate systemic inflammation may be contributory. Mutations in atypical chemokine receptor 1 (ACKR1), otherwise known as the Duffy antigen receptor for chemokines (DARC), confer protection against malaria. Many AAs carry a mutation in the gene encoding this receptor, resulting in loss of its expression. ACKR1 functions as a decoy chemokine receptor, thus dampening chemokine receptor activation and inflammation. Published and preliminary data in humans and mice genetically deficient in ACKR1 suggest that this common gene mutation may contribute to ethnic susceptibility to obesity-related disease, CVD, and cancer. In this narrative review, we present the evidence regarding obesity-related disparities in the bidirectional risk of CVD and cancer and also discuss the potential association of gene polymorphisms in AAs with emphasis on ACKR1.

Intergenerational differences in dietary acculturation among Ghanaian immigrants living in New York City: a qualitative study

Dietary acculturation may explain the increasing risk of diet-related diseases among African immigrants in the United States (US). We interviewed twenty-five Ghanaian immigrants (Youth n 13, Age (Mean ± sd) 20 y ± 5⋅4, Parents (n 6) and Grandparents (n 6) age 58⋅7 ± 9⋅7) living in New York City (NYC) to (a) understand how cultural practices and the acculturation experience influence dietary patterns of Ghanaian immigrants and (b) identify intergenerational differences in dietary acculturation among Ghanaian youth, parents and grandparents. Dietary acculturation began in Ghana, continued in NYC and was perceived as a positive process. At the interpersonal level, parents encouraged youth to embrace school lunch and foods outside the home. In contrast, parents preferred home-cooked Ghanaian meals, yet busy schedules limited time for cooking and shared meals. At the community level, greater purchasing power in NYC led to increased calories, and youth welcomed individual choice as schools and fast food exposed them to new foods. Global forces facilitated nutrition transition in Ghana as fast and packaged foods became omnipresent in urban settings. Adults sought to maintain cultural foodways while facilitating dietary acculturation for youth. Both traditional and global diets evolved as youth and adults adopted new food and healthy social norms in the US.

Anthropometric indices and their cut-off points in relation to type 2 diabetes among Ghanaian migrants and non-migrants: The RODAM study

AIMS

To compare body mass index (BMI), waist circumference (WC) and waist-to-hip ratio (WHR) as determinants of type 2 diabetes (T2DM) and determine optimal cut-offs in a sub-Saharan African population.

METHODS

Data from the RODAM study including Ghanaians aged 25-70 living in rural Ghana, urban Ghana and Europe were used. Logistic regression was used to assess associations between BMI, WC, WHR and T2DM status, by sex and site. Area under the curve (AUC) were constructed to discriminate between indices and establish performance and cut-off values.

RESULTS

WHR had the strongest association with T2DM in men and women across sites, except for rural men. The highest adjusted odds ratio (aOR) and AUC were in rural women for WHR (aOR = 2.09, 95%CI = 1.47-2.99; AUC = 0.71). Among migrants, WHR had higher AUCs compared with BMI (p < 0.01) and WC (p < 0.05). Cut-offs for BMI and WC in men were lower compared with the WHO reference across sites (WC: 85.4-93.7 vs 102 cm, BMI: 23.1-28.2 vs 30.0 kg/m²).

CONCLUSIONS

WHR outperformed BMI and WC as anthropometric indices in relation to T2DM among Ghanaian migrants. The lower BMI and WC cut-offs for T2DM than WHO established standards, highlights the need for African specific cut-offs to avoid missing high risk populations.

Africans Who Arrive in the United States before 20 Years of Age Maintain Both Cardiometabolic Health and Cultural Identity: Insight from the Africans in America Study

The overall consensus is that foreign-born adults who come to America age < 20 y achieve economic success but develop adverse behaviors (smoking and drinking) that lead to worse cardiometabolic health than immigrants who arrive age ≥ 20 y. Whether age of immigration affects the health of African-born Blacks living in America is unknown. Our goals were to examine cultural identity, behavior, and socioeconomic factors and determine if differences exist in the cardiometabolic health of Africans who immigrated to America before and after age 20 y. Of the 482 enrollees (age: 38 ± 1 (mean ± SE), range: 20–65 y) in the Africans in America cohort, 23% (111/482) arrived age < 20 y, and 77% (371/482) arrived age ≥ 20 y. Independent of francophone status or African region of origin, Africans who immigrated age < 20 y had similar or better cardiometabolic health than Africans who immigrated age ≥ 20 y. The majority of Africans who immigrated age < 20 y identified as African, had African-born spouses, exercised, did not adopt adverse health behaviors, and actualized early life migration advantages, such as an American university education. Due to maintenance of cultural identity and actualization of opportunities in America, cardiometabolic health may be protected in Africans who immigrate before age 20. In short, immigrant health research must be cognizant of the diversity within the foreign-born community and age of immigration.

The OGTT is highly reproducible in Africans for the diagnosis of diabetes: Implications for treatment and protocol design

Whether an OGTT reproducibly detects either type 2 diabetes (T2D) or prediabetes in Africans in unknown. Therefore, 131 Africans had two OGTT. Diagnostic reproducibility for T2D was excellent (κ = 0.84), but only moderate for prediabetes (κ = 0.51). A single OGTT positive for T2D may be sufficient to guide clinical care and inform epidemiologic study design. ClinicalTrials.gov Identifier: NCT00001853.

Identifying Africans with undiagnosed diabetes: Fasting plasma glucose is similar to the hemoglobin A1C updated Atherosclerosis Risk in Communities diabetes prediction equation

AIMS

Seventy percent of Africans living with diabetes are undiagnosed. Identifying who should be referred for testing is critical. Therefore we evaluated the ability of the Atherosclerosis Risk in Communities (ARIC) diabetes prediction equation with A1C added (ARIC + A1C) to identify diabetes in 451 African-born blacks living in America (66% male; age 38 ± 10y (mean ± SD); BMI 27.5 ± 4.4 kg/m²).

METHODS

All participants denied a history of diabetes. OGTTs were performed. Diabetes diagnosis required 2-h glucose ≥200 mg/dL. The five non-invasive (Age, parent history of diabetes, waist circumference, height, systolic blood pressure) and four invasive variables (Fasting glucose (FPG), A1C, triglycerides (TG), HDL) were obtained. Four models were tested: Model-1: Full ARIC + A1C equation; Model-2: All five non-invasive variables with one invasive variable excluded at a time; Model-3: All five non-invasive variables with one invasive variable included at a time; Model-4: Each invasive variable singly. Area under the receiver operator characteristic curve (AROC) predicted diabetes. Youden Index identified optimal cut-points.

RESULTS

Diabetes occurred in 7% (30/451). Model-1, the full ARIC + A1C equation, AROC = 0.83. Model-2: With FPG excluded, AROC = 0.77 (P = 0.038), but when A1C, HDL or TG were excluded AROC remained unchanged. Model-3 with all non-invasive variables and FPG alone, AROC=0.87; but with A1C, TG or HDL included AROC declined to ≤0.76. Model-4: FPG as a single predictor, AROC = 0.87. A1C, TG, or HDL as single predictors all had AROC ≤ 0.74. Optimal cut-point for FPG was 100 mg/dL.

CONCLUSIONS

To detect diabetes, FPG performed as well as the nine-variable updated ARIC + A1C equation.

Improved Detection of Abnormal Glucose Tolerance in Africans: The Value of Combining Hemoglobin A1c With Glycated Albumin

OBJECTIVE

In African-born Blacks living in America, we determined by BMI category 1) prevalence of abnormal glucose tolerance (Abnl-GT) and 2) diagnostic value and reproducibility of hemoglobin A_1c (HbA_1c), fructosamine, and glycated albumin (GA).

RESEARCH DESIGN AND METHODS

Participants (n = 416; male, 66%; BMI 27.7 ± 4.5 kg/m² [mean ± SD]) had an oral glucose tolerance test with HbA_1c, GA, and fructosamine assayed. These glycemic markers were repeated 11 ± 7 days later. Abnl-GT diagnosis required 0 h ≥5.6 mmol/L (≥100 mg/dL) and/or 2 h ≥7.8 mmol/L (≥140 mg/dL). Thresholds for HbA_1c, GA, and fructosamine were the values at the 75th percentile for the population (39 mmol/mol [5.7%], 14.2%, and 234 μmol/L, respectively).

RESULTS

Abnl-GT prevalence in the nonobese was 34% versus 42% in the obese (P = 0.124). Reproducibility was excellent for HbA_1c and GA (both κ ≥ 0.8), but moderate for fructosamine (κ = 0.6). Focusing on HbA_1c and GA in the nonobese, we found as single tests the sensitivities of HbA_1c and GA were 36% versus 37% (P = 0.529). Combining HbA_1c and GA, sensitivity increased to 58% because GA identified 37% of Africans with Abnl-GT not detected by HbA_1c (P value for both tests vs. HbA_1c alone was <0.001). For the obese, sensitivities for HbA_1c, GA, and the combined tests were 60%, 27%, and 67%, respectively. Combined test sensitivity did not differ from HbA_1c alone (P = 0.25) because GA detected only 10% of obese Africans with Abnl-GT not detected by HbA_1c.

CONCLUSIONS

Adding GA to HbA_1c improves detection of Abnl-GT in nonobese Africans.

Stress Measured by Allostatic Load Varies by Reason for Immigration, Age at Immigration, and Number of Children: The Africans in America Study

Stress leads to physiologic dysfunction and cardiometabolic disease. Allostatic load score (ALS) measures stress-induced cardiovascular, metabolic, and inflammatory biomarkers. We estimated the odds of high ALS by reason for and age at immigration, duration of American residence, number of children, and socioeconomic status in 193 African immigrants (male: 65%, age 41 ± 10 y (mean ± Standard Deviation (SD)), range 22–65 y). ALS was calculated with High-ALS defined as ALS ≥ 3.0 and Low-ALS defined as ALS < 3.0. Oral glucose tolerance tests (OGTT) were performed, the cardiovascular disease (CVD) risk estimated, and TNF-α, an inflammatory cytokine, measured. Logistic regression was used to estimate odds of High-ALS. In the High- and Low-ALS groups, ALS were 4.0 ± 1.2 vs. 1.3 ± 0.7, diabetes prevalence: 14% vs. 4%, CVD risk: 23% vs. 8%, TNF-α levels: 15 ± 9 vs. 11 ± 6 pg/mL, respectively (all p ≤ 0.01). Immigrants were more likely to be in the High-ALS group if their reason for immigration was work or asylum/refugee (OR 2.18, p = 0.013), their age at immigration was ≥30 y (OR 3.28, p < 0.001), their duration of residence in United States was ≥10 y (OR 3.16, p = 0.001), or their number of children was ≥3 (OR 2.67, p = 0.019). Education, income, health insurance, marital status, and gender did not affect High-ALS odds. Factors adversely influencing allostatic load and cardiometabolic health in African immigrants were age at and reason for immigration, duration of residence in America, and number of children.

Body adiposity measured by bioelectrical impedance is an alternative to dual-energy x-ray absorptiometry in black Africans: The Africans in America Study

OBJECTIVES

The prevalence of cardiometabolic disease has risen in Africa and parallels the obesity epidemic. To assess cardiometabolic risk, body composition measurements by dual-energy X-ray absorptiometry (DXA) are ideal. In communities with limited resources, alternative measures may be useful but have not been compared extensively in black Africans. Therefore, the aim of this study was to identify alternative methods of body composition assessment, such as body adiposity index (BAI) and bioelectrical impedance analysis (BIA), for use in African-born blacks.

METHODS

This was a cross-sectional study with African-born blacks. BAI and five BIA predictive equations (using variations of height, weight, age, sex, and impedance) were compared with DXA to estimate percent fat. Participants were 266 African-born blacks (39 ± 10 y, body mass index 28 ± 4 kg/m², and 68% men) living in metropolitan Washington DC. Equivalence (90% confidence interval, -3 to 3), concordance, and Bland-Altman analyses (bias <2%, R² closest to zero) compared BAI or BIA predictive equations to DXA as the criterion method.

RESULTS

DXA percent fat was 27.2% ± 5.5% and 40.3% ± 6.9% in men and women, respectively. BAI underestimated percent fat in men (bias: 1.88 ± 4.71, R² = 0.25, P < 0.001) and women (bias: 6.47 ± 4.94, R² = 0.08, P = 0.01). Of the five BIA predictive equations, the equation reported by Sun et al. had the best agreement with DXA percent fat for men (bias: -0.91 ± 3.67, R² = 0.02, P = 0.05) and women (bias: -0.92 ± 4.02, R² = 0.003, P = 0.58). Percent fat from the Sun et al. equation best agreed with DXA percent fat.

CONCLUSION

BIA with the Sun et al. predictive equation was the best alternative to DXA for body fat assessment in African-born blacks.

Metabolic characteristics of Africans with normal glucose tolerance and elevated 1-hour glucose: insight from the Africans in America study

INTRODUCTION

Risk of insulin resistance, dyslipidemia, diabetes and cardiac death is increased in Asians and Europeans with normal glucose tolerance (NGT) and 1-hour glucose ≥8.6 mmol/L. As African descent populations often have insulin resistance but a normal lipid profile, the implications for Africans with NGT and glucose ≥8.6 mmol/L (NGT-1-hour-high) are unknown.

OBJECTIVE

We performed oral glucose tolerance tests (OGTTs) in 434 African born-blacks living in Washington, DC (male: 66%, age 38±10 years (mean±SD)) and determined in the NGT group if either glucometabolic or lipid profiles varied according to a 1-hour-glucose threshold of 8.6 mmol/L.

METHODS

Glucose tolerance category was defined by OGTT criteria. NGT was subdivided into NGT-1-hour-high (glucose ≥8.6 mmol/L) and NGT-1-hour-normal (glucose <8.6 mmol/L). Second OGTT were performed in 27% (119/434) of participants 10±7 days after the first. Matsuda Index and Oral Disposition Index measured insulin resistance and beta-cell function, respectively. Lipid profiles were obtained. Comparisons were by one-way analysis of variance with Bonferonni corrections for multiple comparisons. Duplicate tests were assessed by к-statistic.

RESULTS

One-hour-glucose ≥8.6 mmol/L occurred in 17% (47/272) with NGT, 72% (97/134) with pre-diabetes and in 96% (27/28) with diabetes. Both insulin resistance and beta-cell function were worse in NGT-1-hour-high than in NGT-1-hour-normal. Dyslipidemia occurred in both the diabetes and pre-diabetes groups but not in either NGT group. One-hour glucose concentration ≥8.6 mmol/L showed substantial agreement for the two OGTTs (к=0.628).

CONCLUSIONS

Although dyslipidemia did not occur in either NGT group, insulin resistance and beta-cell compromise were worse in NGT-1 hour-high. Subdividing the NGT group at a 1-hour glucose threshold of 8.6 mmol/L may stratify risk for diabetes in Africans.

The trend in blood pressure and hypertension prevalence in the general population of South Kivu between 2012 and 2016: Results from two representative cross-sectional surveys-The Bukavu observational study

Objective

Data on blood pressure trends are scarce or unavailable in Sub-Saharan Africa in general and especially in the Democratic Republic of the Congo. This work addresses this gap by analyzing the dynamics in the prevalence and control of hypertension in a cohort of Congolese adults in South Kivu.

Methods

Two phases of data collection were conducted including a baseline at the beginning in 2012 and a follow up in 2016. The subjects were ≥ 18 years old living in urban (n = 4413) or rural areas (n = 6453). Hypertension was defined as a blood pressure ≥ 140/90 mmHg and/or taking antihypertensive medications. The crude prevalence of hypertension was age-adjusted to the WHO population.

Results

Between 2012 and 2016, there was a significant increase in blood pressure (+2.5/+1.4 mmHg; p = 0.001), age standardized prevalence of hypertension [19.0% vs. 18.0%; OR = 1.05 (1.02–1.08); p<0.0001], and obesity (7.9% to 9.8%; p<0.0001) as well as the proportion of subjects > 60 years old (8.8% to 11.3%; p<0.0001) and those with tachycardia (10.5% to 14.4%; p<0.0001). The number of subjects under treatment of hypertension were statistically non-significant [16.1% vs. 14.3%; p = 0.29), but the level of control of hypertension was significantly reduced by 32.4% in 2016 compared in 2012 (43.5% vs. 64.4%; p = 0.0008).

Conclusion

There was an increase in the prevalence of hypertension as well as cardiovascular-associated risk factors in the population. However, this trend did not increase for treated subjects with no improvements in the level of AHT control. Therefore, improved strategies for the prevention and management of non-communicable diseases are very important in Sub-Saharan Africa.

A Review of Diabetes Prediction Equations in African Descent Populations

Background: Predicting undiagnosed diabetes is a critical step toward addressing the diabetes epidemic in populations of African descent worldwide. Objective: To review characteristics of equations developed, tested, or modified to predict diabetes in African descent populations. Methods: Using PubMed, Scopus, and Embase databases, a scoping review yielded 585 research articles. After removal of duplicates (n = 205), 380 articles were reviewed. After title and abstract review 328 articles did not meet inclusion criteria and were excluded. Fifty-two articles were retained. However, full text review revealed that 44 of the 52 articles did not report findings by AROC or C-statistic in African descent populations. Therefore, eight articles remained. Results: The 8 articles reported on a total of 15 prediction equation studies. The prediction equations were of two types. Prevalence prediction equations (n = 9) detected undiagnosed diabetes and were based on non-invasive variables only. Non-invasive variables included demographics, blood pressure and measures of body size. Incidence prediction equations (n = 6) predicted risk of developing diabetes and used either non-invasive variables or both non-invasive and invasive. Invasive variables required blood tests and included fasting glucose, high density lipoprotein-cholesterol (HDL), triglycerides (TG), and A1C. Prevalence prediction studies were conducted in the United States, Africa and Europe. Incidence prediction studies were conducted only in the United States. In all these studies, the performance of diabetes prediction equations was assessed by area under the receiver operator characteristics curve (AROC) or the C-statistic. Therefore, we evaluated the efficacy of these equations based on standard criteria, specifically discrimination by either AROC or C-statistic were defined as: Poor (0.50 - 0.69); Acceptable (0.70 - 0.79); Excellent (0.80 - 0.89); or Outstanding (0.90 - 1.00). Prediction equations based only on non-invasive variables reported to have poor to acceptable detection of diabetes with AROC or C-statistic 0.64 - 0.79. In contrast, prediction equations which were based on both non-invasive and invasive variables had excellent diabetes detection with AROC or C-statistic 0.80 - 0.82. Conclusion: Equations which use a combination of non-invasive and invasive variables appear to be superior in the prediction of diabetes in African descent populations than equations that rely on non-invasive variables alone.

A1C Underperforms as a Diagnostic Test in Africans Even in the Absence of Nutritional Deficiencies, Anemia and Hemoglobinopathies: Insight From the Africans in America Study

Introduction: To improve detection of undiagnosed diabetes in Africa, there is movement to replace the OGTT with A1C. The performance of A1C in the absence of hemoglobin-related micronutrient deficiencies, anemia and heterozygous hemoglobinopathies is unknown. Therefore, we determined in 441 African-born blacks living in America [male: 65% (281/441), age: 38 ± 10 y (mean ± SD), BMI: 27.5 ± 4.4 kg/m²] (1) nutritional and hematologic profiles and (2) glucose tolerance categorization by OGTT and A1C. Methods: Hematologic and nutritional status were assessed. Hemoglobin <11 g/dL occurred in 3% (11/441) of patients and led to exclusion. A1C and OGTT were performed in the remaining 430 participants. ADA thresholds for A1C and OGTT were used. Diagnosis by A1C required meeting either A1C-alone or A1C&OGTT criteria. Diagnosis by OGTT-alone required detection by OGTT and not A1C. Results: Hemoglobin, mean corpuscular volume and red blood cell distribution width were 14.0 ± 1.3 g/dL, 85.5 ± 5.3 fL, and 13.2 ± 1.2% respectively. B12, folate, and iron deficiency occurred in 1% (5/430), 0% (0/430), and 4% (12/310), respectively. Heterozygous hemoglobinopathy prevalence was 18% (78/430). Overall, diabetes prevalence was 7% (32/430). A1C detected diabetes in 32% (10/32) but OGTT-alone detected 68% (22/32). Overall prediabetes prevalence was 41% (178/430). A1C detected 57% (102/178) but OGTT-alone identified 43% (76/178). After excluding individuals with heterozygous hemoglobinopathies, the rate of missed diagnosis by A1C of abnormal glucose tolerance did not change (OR: 0.99, 95% CI: 0.61, 1.62). Conclusions: In nutritionally replete Africans without anemia or heterozygous hemoglobinopathy, if only A1C is used, ~60% with diabetes and ~40% with prediabetes would be undiagnosed. Clinical Trial Registration:: www.ClinicalTrials.gov, Identifier: NCT00001853.