Roland Dyck

Epidemiology of diabetes mellitus among First Nations and non-First Nations adults

Background: First Nations people in Canada experience a disproportionate burden of type 2 diabetes mellitus. To increase our understanding of this evolving epidemic, we compared the epidemiology of diabetes between First Nations and non-First Nations adults in Saskatchewan from 1980 to 2005. Methods: We used administrative databases to perform a population-based study of diabetes frequency, incidence and prevalence in adults by ethnic background, year, age and sex. Results: We identified 8275 First Nations and 82 306 non-First Nations people with diabetes from 1980 to 2005. Overall, the incidence and prevalence of diabetes were more than 4 times higher among First Nations women than among non-First Nations women and more than 2.5 times higher among First Nations men than among non-First Nations men. The number of incident cases of diabetes was highest among First Nations people aged 40–49, while the number among non-First Nations people was greatest in those aged 70 or more years. The prevalence of diabetes increased over the study period from 9.5% to 20.3% among First Nations women and from 4.9% to 16.0% among First Nations men. Among non-First Nations people, the prevalence increased from 2.0% to 5.5% among women and from 2.0% to 6.2% among men. By 2005, almost 50% of First Nations women and more than 40% of First Nations men aged 60 or older had diabetes, compared with less than 25% of non-First Nations men and less than 20% of non-First Nations women aged 80 or older. Interpretation: First Nations adults are experiencing a diabetes epidemic that disproportionately affects women during their reproductive years. This ethnicity-based pattern suggests diverse underlying mechanisms that may include differences in the diabetogenic impact of gestational diabetes.

The Inter- and Intragenerational Impact of Gestational Diabetes on the Epidemic of Type 2 Diabetes

OBJECTIVES We investigated the contribution of gestational diabetes mellitus (GDM) to the historic epidemic of type 2 diabetes mellitus (T2DM) in Saskatchewan. METHODS We constructed a population-level simulation model of the inter- and intragenerational interaction of GDM and T2DM for the period 1956 to 2006. The model was stratified by gender, ethnicity, and age; parameterized with primary and secondary data; and calibrated to match historic time series. Risk of diabetes was sigmoidally trended to capture exogenous factors. RESULTS Best-fit calibrations suggested GDM may be responsible for 19% to 30% of the cases of T2DM among Saskatchewan First Nations people, but only for approximately 6% of cases among other persons living in Saskatchewan. The estimated contribution of GDM to the growth in T2DM was highly sensitive to assumptions concerning the post-GDM risk of developing T2DM. CONCLUSIONS GDM may be an important driver for the T2DM epidemic in many subpopulations. Because GDM is a readily identifiable, preventable, and treatable condition, investments in prevention, rapid diagnosis, and evidence-based treatment of GDM in at-risk populations may offer substantial benefit in lowering the T2DM burden over many generations. Model-informed data collection can aid in assessing intervention tradeoffs.

Mechanisms of renal disease in indigenous populations: influences at work in Canadian indigenous peoples

Canadian aboriginal people experience end‐stage renal disease at rates 2.5–4 times higher than those found in the general population. Up to 60% of cases are due to diabetic end‐stage renal disease, while most of the remainder are caused by a variety of types of glomerulonephritis. The greatest increase in cases of end‐stage renal disease among aboriginal people since 1981 has been observed in those with diabetes. There appear to be three major contributing influences to the increase in diabetic end‐stage renal disease among Canadian aboriginal people. First, the rates of type 2 diabetes mellitus have increased from virtually zero to several times those seen in the general population in less than 60 years. Second, aboriginal people with diabetes have seven times the rate of diabetic end‐stage renal disease compared with their non‐aboriginal counterparts. Finally, birth rates among aboriginal people are higher than in any other segment of the population. An epidemic of diabetic end‐stage renal disease is the most important nephrological issue facing Canadian aboriginal people and threatens to overwhelm health care resources in many parts of the country unless effective early recognition and prevention programmes are established.

Methods of competing risks analysis of end-stage renal disease and mortality among people with diabetes

BackgroundWhen a patient experiences an event other than the one of interest in the study, usually the probability of experiencing the event of interest is altered. By contrast, disease-free survival time analysis by standard methods, such as the Kaplan-Meier method and the standard Cox model, does not distinguish different causes in the presence of competing risks. Alternative approaches use the cumulative incidence estimator by the Cox models on cause-specific and on subdistribution hazards models. We applied cause-specific and subdistribution hazards models to a diabetes dataset with two competing risks (end-stage renal disease (ESRD) or death without ESRD) to measure the relative effects of covariates and cumulative incidence functions.ResultsIn this study, the cumulative incidence curve of the risk of ESRD by the cause-specific hazards model was revealed to be higher than the curves generated by the subdistribution hazards model. However, the cumulative incidence curves of risk of death without ESRD based on those three models were very similar.ConclusionsIn analysis of competing risk data, it is important to present both the results of the event of interest and the results of competing risks. We recommend using either the cause-specific hazards model or the subdistribution hazards model for a dominant risk. However, for a minor risk, we do not recommend the subdistribution hazards model and a cause-specific hazards model is more appropriate. Focusing the interpretation on one or a few causes and ignoring the other causes is always associated with a risk of overlooking important features which may influence our interpretation.

Differential mortality and the excess burden of end-stage renal disease among First Nations people with diabetes mellitus: a competing-risks analysis

Background: Diabetes-related end-stage renal disease disproportionately affects indigenous peoples. We explored the role of differential mortality in this disparity. Methods: In this retrospective cohort study, we examined the competing risks of end-stage renal disease and death without end-stage renal disease among Saskatchewan adults with diabetes mellitus, both First Nations and non–First Nations, from 1980 to 2005. Using administrative databases of the Saskatchewan Ministry of Health, we developed Fine and Gray subdistribution hazards models and cumulative incidence functions. Results: Of the 90 429 incident cases of diabetes, 8254 (8.9%) occurred among First Nations adults and 82 175 (90.9%) among non–First Nations adults. Mean age at the time that diabetes was diagnosed was 47.2 and 61.6 years, respectively (p < 0.001). After adjustment for sex and age at the time of diabetes diagnosis, the risk of end-stage renal disease was 2.66 times higher for First Nations than non–First Nations adults (95% confidence interval [CI] 2.24–3.16). Multivariable analysis with adjustment for sex showed a higher risk of death among First Nations adults, which declined with increasing age at the time of diabetes diagnosis. Cumulative incidence function curves stratified by age at the time of diabetes diagnosis showed greatest risk for end-stage renal disease among those with onset of diabetes at younger ages and greatest risk of death among those with onset of diabetes at older ages. Interpretation: Because they are typically younger when diabetes is diagnosed, First Nations adults with this condition are more likely than their non–First Nations counterparts to survive long enough for end-stage renal disease to develop. Differential mortality contributes substantially to ethnicity-based disparities in diabetes-related end-stage renal disease and possibly to chronic diabetes complications. Understanding the mechanisms underlying these disparities is vital in developing more effective prevention and management initiatives.

Prevalence, risk factors and co-morbidities of diabetes among adults in rural Saskatchewan: the influence of farm residence and agriculture-related exposures

BackgroundAlthough rural Canadians are reported to have higher rates of diabetes than others, little is known about the relative influence of known versus agriculture-related risk factors. The purpose of this research was to carry out a comprehensive study of prevalence, risk factors and co-morbidities of diabetes among adults in rural Saskatchewan and to determine possible differences between those living on and off farms.MethodsIn 2010, we conducted a baseline mail-out survey (Saskatchewan Rural Health Study) of 11,982 households located in the province′s four agricultural quadrants. In addition to self-reported physician-diagnosed diabetes, the questionnaire collected information from farm and small town cohorts on possible diabetes determinants including lifestyle, family history, early life factors and environmental/agricultural-related exposures. Clustering effect within households was adjusted using Generalized Estimating Equations approach.ResultsResponses were obtained from 4624 (42%) households comprising 8208 males and females aged 18 years or older and 7847 self-described Caucasian participants (7708 with complete information). The overall age-standardized diabetes prevalence for the latter was 6.35% but people whose primary residence was on farms had significantly lower diabetes prevalence than those living in non-farm locations (5.11% versus 7.33% respectively; p<0.0001). Diabetes risk increased with age and affected almost 17% of those older than 65 (OR 2.57; CI′ 1.63, 4.04 compared to those aged 18–45). Other known independent risk factors included family history of diabetes (OR 2.50 [CI′s 1.94, 3.23] if father; OR 3.11 [CI′s 2.44, 3.98] if mother), obesity (OR 2.66; CI′s 1.86, 3.78), as well as lower socioeconomic status, minimal/no alcohol intake and smoking. The most original finding was that exposure to insecticides conferred an increased risk for diabetes among males (OR 1.83; CI′s 1.15, 2.91). Finally, the co-morbidities with the strongest independent association with diabetes were heart disease and hypertension.ConclusionsWhile known diabetes risk factors are important determinants of diabetes in the agricultural zones of Saskatchewan, on-farm residence is protective and appears related to increased outdoor activities. In contrast, we have now shown for the first time that exposure to insecticides is an independent risk factor for diabetes among men in rural Canada.

Prevalence, determinants and co-morbidities of chronic kidney disease among First Nations adults with diabetes: results from the CIRCLE study

BackgroundIndigenous peoples worldwide are experiencing elevated rates of type 2 diabetes and its complications. To better understand the disproportionate burden of diabetic end stage renal disease (ESRD) among Canadian First Nations people (FN), we examined prevalence, determinants, and co-morbidities of chronic kidney disease (CKD) within this population.MethodsThe 2007 Canadian FN Diabetes Clinical Management and Epidemiologic (CIRCLE) study conducted a cross-sectional national medical chart audit of 885 FN adults with type 2 diabetes to assess quality of diabetes care. In this sub-study, participants were divided by estimated glomerular filtration rate (eGFR in ml/min/1.73 m2), as well as by albuminuria level in those with eGFRs = > 60. Those with eGFRs = > 60 and negative albuminuria were considered to have normal/near normal kidney function (non-CKD). Using univariate and logistic regression analysis, they were compared with participants having eGFRs = > 60 plus albuminuria (CKD-alb) and with participants having eGFRs <60 (CKD-eGFR <60).ResultsWhile 84.5% of total CIRCLE participants had eGFRs = > 60, almost 60% of the latter had CKD-alb. Of the 15.5% of total participants with CKD-eGFR <60, 80% had eGFRs 30–60 (Stage 3 CKD) but over 10% (1.6% of total participants) had ESRD. Independent determinants of CKD-alb were male gender and increasing diabetes duration, systolic BP, A1C and total cholesterol. These plus smoking rates also discriminated between FN with micro- and macro-albuminuria. Independent determinants of CKD-eGFR <60 were increasing age at diabetes diagnosis, diabetes duration, total cholesterol and systolic BP. However, participants with CKD-eGFR <60 also displayed a decreasing mean age of diabetes diagnosis as eGFR declined. Micro-vascular co-morbidities were significantly associated with CKD-alb but both micro- and macro-vascular co-morbidities were associated with CKD-eGFR <60. Only 35-40% of participants with CKD used insulin.ConclusionsHigh prevalences of CKD-alb and early CKD-eGFR <60 among diabetic FN were largely related to modifiable and treatable risk factors. However, an earlier age of diabetes diagnosis and longer duration of diabetes characterized those with ESRD. These findings suggest that a failure to meet current standards of diabetes care interacting with an age-related survival benefit contribute to the disproportionate burden of ESRD among FN and possibly other Indigenous peoples.

A Novel System Dynamics Model of Female Obesity and Fertility

OBJECTIVES Our objective was to create a system dynamics model specific to weight gain and obesity in women of reproductive age that could inform future health policies and have the potential for use in preconception interventions targeting obese women. METHODS We used our system dynamics model of obesity in women to test various strategies for family building, including ovulation induction versus weight loss to improve ovulation. Outcomes included relative fecundability, postpartum body mass index, and mortality. RESULTS Our system dynamics model demonstrated that obese women who become pregnant exhibit increasing obesity levels over time with elevated morbidity and mortality. Alternatively, obese women who lose weight prior to pregnancy have improved reproductive outcomes but may risk an age-related decline in fertility, which can affect overall family size. CONCLUSIONS Our model highlights important public health issues regarding obesity in women of reproductive age. The model may be useful in preconception counseling of obese women who are attempting to balance the competing risks associated with age-related declines in fertility and clinically meaningful weight loss.

An association of maternal age and birth weight with end-stage renal disease in Saskatchewan: Sub-analysis of registered Indians and those with diabetes

Aims: To determine links between birth related factors and end-stage renal disease (ESRD). Methods: This 1:3 age, sex, and source population (registered Indians [SkRI] and other Saskatchewan people [OSkP]) matched case-control study, compared maternal age and parity, gestational age, low birth weight (LBW), and high birth weight (HBW), between subjects with and without ESRD. Results: Of 1,162 subjects, 277 cases (48 SkRI and 229 OSkP) and 601 controls (112 SkRI and 489 OSkP) had birth weight information. A trend for increased LBW rates occurred among SkRI and OSkP cases compared to controls (10.4 vs. 5.3% and 6.6 vs. 4.3%), and was significant for OSkP female cases (OR 3.66; 95% confidence interval [CI] 1.05, 12.73). Higher HBW rates occurred in SkRI cases (14.6% compared to 11.6% controls; N/S), and 3/5 female SkRI diabetic ESRD (DESRD) cases were over 3,750 g compared to 1/14 controls (p < 0.05). Only maternal age ≧30 years was an independent predictor for ESRD, particularly for OSkP non-DESRD cases (OR 2.45; 95% CI 1.03, 5.8). Cases with older mothers had lower mean birth weights than controls (3,236 vs. 3,434 g; p = 0.005). Conclusions: Older maternal age may predispose offspring to ESRD through mechanisms that differ for DESRD versus non-DESRD, and that may relate to ethnicity.

End Stage Renal Disease Among People with Diabetes: A Comparison of First Nations People and Other Saskatchewan Residents from 1981 to 2005

ABSTRACT OBJECTIVE: Since First Nations people (FN) with diabetes experience higher rates of end-stage renal disease (ESRD) than others, we aimed to better understand these disparities by comparing the epidemiology of ESRD between FN and other Saskatchewan residents (OSK) with diabetes over a prolonged period. METHODS: We used healthcare system administrative databases to determine ESRD rates, distribution and mortality by ethnicity, age and sex among total diabetes populations in Saskatchewan from 1981 to 2005. RESULTS: Although similar initially, ESRD incidence among FN with diabetes peaked at levels 3 to 4 times higher than OSK with diabetes by 1991 to 1996. Differences in ESRD prevalence between diabetes populations were less pronounced. OSK men with diabetes experienced higher ESRD rates than OSK women with diabetes, while sex differences among FN were variable. FN with diabetes and ESRD were younger than OSK at diabetes diagnosis and experienced a longer time from diabetes to ESRD diagnosis. However, survival of FN adults with diabetes after ESRD diagnosis was reduced compared to others. CONCLUSIONS: Ethnicity-based disparities in ESRD incidence among people with diabetes remain pronounced, particularly among women. Differential mortality pre-ESRD may contribute to these differences, because FN are younger at diabetes diagnosis. This favours longer survival and increased exposure to the metabolic consequences of diabetes.