Mahomed A.K. Omar

The Prevalence of Metabolic Syndrome and Determination of the Optimal Waist Circumference Cutoff Points in a Rural South African Community

OBJECTIVE To determine the prevalence of metabolic syndrome and to define optimal ethnic-specific waist-circumference cutoff points in a rural South African black community. RESEARCH DESIGN AND METHODS This was a cross-sectional survey conducted by random-cluster sampling of adults aged >15 years. Participants had demographic, anthropometric, and biochemical measurements taken, including a 75-g oral glucose tolerance test. Metabolic syndrome was defined using the 2009 Joint Interim Statement (JIS) definition. RESULTS Of 947 subjects (758 women) studied, the age-adjusted prevalence of metabolic syndrome was 22.1%, with a higher prevalence in women (25.0%) than in men (10.5%). Peak prevalence was in the oldest age-group (≥65 years) in women (44.2%) and in the 45- to 54-year age-group in men (25.0%). The optimal waist circumference cutoff point to predict the presence of at least two other components of the metabolic syndrome was 86 cm for men and 92 cm for women. The crude prevalence of metabolic syndrome was higher with the JIS definition (26.5%) than with the International Diabetes Federation (IDF) (23.3%) or the modified Third Report of the National Cholesterol Education Program Adult Treatment Panel (ATPIII) (18.5%) criteria; there was very good agreement with the IDF definition (κ = 0.90 [95% CI 0.87–0.94]) and good concordance with ATPIII criteria (0.77 [0.72–0.82]). CONCLUSIONS There is a high prevalence of metabolic syndrome, especially in women, suggesting that this community, unlike other rural communities in Africa, already has entered the epidemic of metabolic syndrome. Waist circumference cutoff points differ from those currently recommended for Africans.

Diabetes and Other Disorders of Glycemia in a Rural South African Community: Prevalence and associated risk factors

OBJECTIVE—The purpose of this study was to determine the prevalence of diabetes, impaired glucose tolerance (IGT), impaired fasting glycemia (IFG), and associated risk factors in a rural South African black community. RESEARCH DESIGN AND METHODS—This was a cross-sectional survey conducted by random cluster sampling of adults aged >15 years. Participants had a 75-g oral glucose tolerance test using the 1998 World Health Organization criteria for disorders of glycemia. RESULTS—Of 1,300 subjects selected, 1,025 subjects (815 women) participated (response rate 78.9%). The overall age-adjusted prevalence of diabetes was 3.9%, IGT 4.8%, and IFG 1.5%. The prevalence was similar in men and women for diabetes (men 3.5%; women 3.9%) and IGT (men 4.6%; women 4.7%) but higher in men for IFG (men 4.0%; women 0.8%). The prevalence of diabetes and IGT increased with age both in men and women, with peak prevalence in the 55- to 64-year age-group for diabetes and in the ≥65-year age-group for IGT. Of the cases of diabetes, 84.8% were discovered during the survey. In multivariate analysis, the significant independent risk factors associated with diabetes included family history (odds ratio 3.5), alcohol ingestion (2.8), waist circumference (1.1), systolic blood pressure (1.0), serum triglycerides (2.3), and total cholesterol (1.8); hip circumference was protective (0.9). CONCLUSIONS—There is a moderate prevalence of diabetes and a high prevalence of total disorders of glycemia, which suggests that this community, unlike other rural communities in Africa, is well into an epidemic of glucose intolerance. There is a low proportion of known diabetes and a significant association with potentially modifiable risk factors.

Epidemiology of Type 1 and Type 2 Diabetes in Africa

Until recently, there was a paucity of data on the epidemiology of diabetes mellitus in Africa. Over the past decade, information on the prevalence of type 2 diabetes has increased, albeit still limited, but there is still a lack of adequate data on type 1 diabetes in sub-Saharan Africa (SSA). For type 2 diabetes, although the prevalence is low in some rural populations, moderate and even high rates have been reported from other countries. In low diabetes prevalence populations, the moderate to high rates of impaired glucose tolerance is a possible indicator of the early stage of a diabetes epidemic. Diabetes prevalence is higher in urban, migrant and African-origin populations living abroad. There is evidence for a significant association with preventable and modifiable risk factors viz. adiposity, known diabetes, physical activity; but a dearth of data on the impact of dietary and genetic factors. For type 1 diabetes, the limited available data suggest that in SSA the frequency is low and that age of onset occurs later than in the western world. There is evidence for the role of genetic and immunological factors in its pathogenesis. The impact of HIV/AIDS on projected estimates for diabetes prevalence in Africa needs to be established.

South African Indians Show a High Prevalence of NIDDM and Bimodality in Plasma Glucose Distribution Patterns

OBJECTIVE To determine the prevalence of diabetes mellitus and impaired glucose tolerance (IGT) and to test for bimodality in the plasma glucose distribution in South African Indians. RESEARCH DESIGN AND METHODS Subjects were selected by systematic cluster sampling in various areas of Durban. They underwent a modified glucose tolerance test whereby fasting and 2-h postglucose (75 g) plasma glucose levels were measured. The program MIX was used to test for bimodality in the plasma glucose distribution. RESULTS We tested 2,479 subjects (1,441 women and 1,038 men). Based on the revised World Health Organization criteria, the crude prevalence of diabetes mellitus was 9.8%, and the crude prevalence of IGT was 5.8%; the age- and sex-adjusted prevalence was 13.0 and 6.9%, respectively. IGT was significantly more common in men (7.6%) than in women (4.4%). Obesity was a feature of both diabetes mellitus and IGT, particularly in women. Both fasting and 2-h plasma glucose values did not conform to a single normal distribution pattern in any age-group, whereas unequivocal evidence of bimodality was seen in the 55- to 74-year age-group of both sexes for fasting and 2-h glucose and also in the 2-h levels of men in the 25- to 34-year age-group. CONCLUSIONS This study has highlighted a high prevalence of non-insulindependent diabetes mellitus in South African Indians and bimodality in the plasma glucose distribution.

High incidence of Type 2 diabetes mellitus in South African Indians: a 10-year follow-up study

Aims Previous cross‐sectional studies have established that South African Indians have a high prevalence of Type 2 diabetes mellitus. A prospective community study was undertaken to determine the incidence of Type 2 diabetes and the risk factors associated with its development in a cohort of South African Indians who had been studied 10 years previously.

Effect of Insulin Therapy on Blood Pressure in NIDDM Patients With Secondary Failure

OBJECTIVE To assess the effect of insulin therapy on blood pressure in NIDDM patients with secondary failure. RESEARCH DESIGN AND METHODS The influence of insulin treatment on blood pressure was assessed retrospectively in a group of 80 NIDDM patients with secondary failure to diet and maximum doses of oral hypoglycemic agents. Weight, blood glucose, and blood pressure were recorded over a 3-mo period before and after the initiation of insulin therapy. RESULTS There was a significant rise in systolic (131.8 ± 1.7 to 148 ± 1.9 mmHg, P < 0.05) and diastolic (80.9 ± 0.9 to 89.2 ± 1.0 mmHg, P < 0.02) blood pressures with insulin treatment. Insulin treatment was associated with a significant decrease in blood glucose (18.36 ± 0.28 to 10.4 ± 0.34 mM, P < 0.01) and an increase in weight (72.1 ± 1.6 to 78 ± 1.7 kg, P = 0.01). A control group of 80 NIDDM patients matched for age, weight, BMI, and duration of diabetes demonstrated no significant change in blood pressure over a matched period of follow-up. CONCLUSIONS This study has shown that insulin therapy is associated with significant elevation of both systolic and diastolic blood pressures.

High Risk of Progression to NIDDM in South-African Indians with Impaired Glucose Tolerance

A four-yr prospective study was undertaken to examine the natural history of IGT in 128 South-African Indians classified as such at year 0 of the study, based on WHO criteria. Subjects were reexamined at year 1 and year 4. Of the 113 subjects who completed the study, 50.4% progressed to NIDDM (rate of progression 12.6%/yr), 24.8% persisted with IGT, and 24.8%, reverted to NGT. The majority (72%) who progressed to NIDDM did so in year 1. At year 1, 47 subjects were still classified as IGT; of the 40 subjects completing the study, 16 subjects (40%) progressed to NIDDM, 17 subjects (42.5%) persisted with IGT, and 7 subjects (17.5%) reverted to NGT. Examination of risk factors predictive of subsequent progression to NIDDM was undertaken by analysis of baseline variables in two ways: When year 0 was used as baseline (in 113 IGT0 subjects), significant predictive risk factors were the FPG and 2-h plasma glucose concentrations. All subjects who at year 0 had 2-h plasma glucose ≥ 10.2 and < 11.1 mM or FPG ≥ 7.3 but < 7.8 mM, subsequently progressed to NIDDM. When year 1 was used as baseline (40 IGT1 subjects), 90-min plasma glucose concentration (midtest level) was found to be a significant risk factor for development of NIDDM. In conclusion, this study has demonstrated that in South-African Indians with IGT, the majority (50.4%) progress to NIDDM within 4 yr; significant predictors of subsequent diabetes are the baseline fasting and 2-h plasma glucose concentration. The midtest plasma glucose also may be a useful predictor of clinical outcome. Moreover, the study highlighted the rapid decompensation to NIDDM in the first year and the demonstration of cut-off levels of plasma glucose above which the risk of development of NIDDM is total.

Application of the new ADA criteria for the diagnosis of diabetes to population studies in sub‐Saharan Africa

Aimsu2003To examine the implications for epidemiological studies of the American Diabetes Association (ADA) recommendation that the fasting blood glucose at a lowered level becomes the main diagnostic test for diabetes on cross‐sectional‐based data from sub‐Saharan Africa.

Evaluation of WHO and NDDG criteria for impaired glucose tolerance

A 4-year prospective study on the natural history of IGT in South African Indians has allowed for the evaluation of the WHO and NDDG criteria for IGT, using the five groups for non-diabetic glucose tolerance recently recommended and relating these to the risk of diabetes development. Using WHO criteria, 128 subjects were classed IGT in a baseline survey (Year 0). The five recommended categories were applied to the OGTTs done between Year 1 and Year 4 of the study, when mid-test plasma (MPG) samples were also obtained. These categories included N-N (Normal by WHO and NDDG); N-ND1 (Normal by WHO, non-diagnostic level 1 by NDDG); N-ND2 (Normal by WHO, non-diagnostic level 2 by NDDG); I-ND3 (IGT by WHO, non-diagnostic level 3 by NDDG) and I-I (IGT by WHO and NDDG). The risk of diabetes development and the significance of the non-diagnostic category were evaluated by comparing the glucose tolerance status at Year 4 with the status at Year 1. In the cross-sectional evaluation at Year 1, of the 87 non-diabetic OGTTs analysed, 31% (n = 27) were classified I-I, 34.5% (n = 30) were classed N-N and 34.5% (n = 30) were classified non-diagnostic [I-ND3 (23.1%); N-ND2 (8%); N-ND1 (3.4%)]. In the prospective analysis, of the 72 subjects who completed the study, 16 subjects developed NIDDM by Year 4; of these 13 subjects were classed I-I and 3 subjects I-ND3 at Year 1.(ABSTRACT TRUNCATED AT 250 WORDS)

HLA-A, B, C and DR antigens in young South African blacks with Type 1 (insulin-dependent) diabetes mellitus

SummaryThe HLA status of South African black Type 1 (insulin-dependent) diabetic patients with age of onset under 35 years was compared with that of healthy black control subjects. HLA-A, B and C antigens were determined in 94 patients and 995 control subjects, while DR typing was carried out on 56 patients and 195 control subjects. There was a significant increase in the frequency of DR4 in patients as compared with control subjects (P < 0.01; relative risk 3.4). DR3/DR4 heterozygosity was associated with a greater relative risk for developing Type 1 diabetes mellitus (3.7) than the presence of DR3 alone (relative risk 1.6). A significant negative association was observed between the presence of BW42 and Type 1 diabetes in this population sample (P < 0.04; relative risk 0.3). A similar trend was observed with regard to DR2, the corrected p value just attaining statistical significance (p < 0.05; relative risk 0.1).