Predictors of A1c among women with a history of gestational diabetes inAboriginal communities of AlbertaRichard T. Oster, ...
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Predictors of A1c among women with a history of gestational diabetes in Aboriginal communities of Alberta


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2012 University of Alberta - Department of Medicine Research Day, poster presentation by Richard Oster

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Predictors of A1c among women with a history of gestational diabetes in Aboriginal communities of Alberta

  1. 1. Predictors of A1c among women with a history of gestational diabetes inAboriginal communities of AlbertaRichard T. Oster, Ellen L. TothDepartment of Medicine, University of AlbertaCanadian Aboriginal IssuesDatabase, Affairs andNorthern DevelopmentCanada, www.ainc-inac.gc.ca1. BackgroundThe prevalence of type 2 diabetes is increasing, seemingly unabated (1). Many CanadianAboriginal populations suffer type 2 diabetes rates that are 2-5 times higher than thenon-Aboriginal population (2, 3), with Aboriginal women being disproportionatelyaffected (4). It is believed that a complex combination of social, cultural, environmentaland genetic factors are at play. In attempts to further understand the causes, the possiblecontribution of gestational diabetes (GD) has received recent attention. In Aboriginalpopulations, it is suggested that GD contributes to a vicious cycle by increasing the risk oftype 2 diabetes in both offspring and mothers (5).Both the American Diabetes Association and Canadian Diabetes Association nowrecommend the use of glycated hemoglobin (A1c) ≥ 6.5% for the diagnosis of diabetes. A1cindicates the average blood glucose concentrations over the previous 2-3 months and hasbeen used for decades as a measure of risk for the development of complications and as ameasure of quality of diabetes care. Among people without diagnosed diabetes, there isincreasing evidence demonstrating the usefulness of A1c in predicting potential risk ofdiabetes (6).Given the growing evidence of the ability of hemoglobin A1c to forecast future diabetes,we sought to examine the predictors of A1c among non-diabetic women (mostlyAboriginal) with a history of GD in the province of Alberta.2. MethodsWe accessed the databases of three separate community-based diabetes and riskscreening projects. Subjects self-referred from Aboriginal and rural communities in Alberta.Subjects were screened with clinical exams and portable lab technology between the years2003-2011. A1c, body mass index (BMI), waist circumference, fasting or random glucose,total cholesterol, high-density lipoprotein (HDL) cholesterol, blood pressure, as well as thepresence of metabolic syndrome and family history of diabetes was assessed.K3. ResultsA total of 184 adult (≥ 20 years) women with previous GD were screened. Of thesewomen, 114 were First Nations, 40 were Métis, and 30 were non-Aboriginal. Ethnicdifferences in age and percent with low HDL cholesterol were observed.In the final adjusted model, significant associations remained only for waistcircumference (beta coefficient 0.018; 95% CI 0.007 - 0.031; p = 0.02) and age (betacoefficient 0.018; 95% CI 0.010 - 0.026; p <0.001). In other words, for a one unitincrease in waist circumference, A1c increases by 0.018 in the model (on average).Likewise, for a one unit increase in age, A1c increases by 0.018 (on average). Aboriginalethnicity was not associated with A1c.Non-Aboriginal(N=30)First Nations(N=114)Métis(N=40)P-value*age 47.8 ± 11.78 37.7 ± 10.03 37.5 ± 9.36 <0.001A1c 5.5 ± 0.49 5.4 ± 0.58 5.6 ± 0.94 0.32% with undiagnoseddiabetes3.3%(0.08-17.22)5.3%(1.96-11.10)12.5%(4.19-26.80)0.21% with hypertension 24.1%(10.30-43.54)18.4%(7.74-34.33)11.1%(3.11-26.06)0.38% overweight or obese 82.1%(63.11-93.94)88.1%(80.47-93.49)82.1%(66.47-92.47)0.53% with high waistcircumference75.9%(56.46-89.70)88.6%(80.89-93.95)79.0%(62.68-90.45)0.13% withhypertriglyceridemia86.7%(69.28-96.24)83.3%(74.94 – 89.81)81.2%(65.67-92.26)0.85% with low HDL 3.6%(0.09-18.35)21.9%(13.08-33.14)17.1%(6.56-33.65)0.04% with high totalcholesterol : HDL ratio3.6%(0.09-18.35)15.2%(7.22-26.99)17.4%(6.56-33.65)0.21% with metabolicsyndrome16.7%(5.64-34.72)25.4%(17.75-34.45)17.5%(7.34-32.78)0.42% with family diabeteshistory71.4%(51.33-86.78)68.9%(59.06-77.69)86.1%(70.50-95.33)0.13% with sibling diabeteshistory26.7%(12.28-45.89)26.3%(18.51-35.39)17.5%(7.34-32.79)0.51Characteristics of women with a history of GD. Values are means ± SD orprevalence (95% CI).* p-values are for overall differences calculated using ANOVA or Chi-square as appropriateBeta coefficient P-valueSystolic blood pressure 0.78 0.44Diastolic blood pressure -0.65 0.52BMI -0.68 0.49Waist circumference 2.12 0.03HDL -0.25 0.80Total cholesterol 0.35 0.73Total cholesterol : HDL ratio 0.29 0.77Age 2.06 0.04Family history of diabetes 0.38 0.71Sibling history of diabetes 0.91 0.36Metabolic syndrome 1.54 0.13First Nations ethnicity -1.00 0.32Métis ethnicity 0.54 0.54Results of simple linear regression analysis (univariate)Beta coefficient p-valueWaist circumference 0.02 0.02Age 0.02 <0.001BMI* -0.01 0.29Results of final regression model* BMI was kept in the model as it was a confounder3. ConclusionsIncreasing waist circumference and age are predictive of A1c among women withprevious GD.Analysis of variance and chi-square tests were used to identify any between group(ethnicity) differences. Statistical modeling using multiple regression analysis wasconducted to quantify the relationships between A1c and measured variables.20-29 30-39 40-49 50-59 > 6044.555.566.577.5Age groupA1c(%)< 84.9 85-99.9 100-114.9 115-129.9 >13044.555.566.577.5Waist circumferencegroupA1c(%)Average A1c by age group and waist circumference group4. References1. Shaw JE et al. Diabetes Res Clin Pract. 2010;87(1):4-14.2. Young TK et al. CMAJ. 2000;163(5):561-6.3. King M et al. Lancet. 2009;374(9683):76-85.4. Dyck R et al. CMAJ. 2010;182(3):249-56.5. Osgood ND et al. Am J Public Health. 2011;101(1):173-9.6. Abdul-Ghani MA et al. J Clin Endocrinol Metab. 2011;96(8):2596-600.h