The Alberta’s Caring for Diabetes (ABCD) Study: Rationale, Design and Baseline Characteristics of a Prospective Cohort of Adults with Type 2 Diabetes

Can J Diabetes xxx (2015) 1e7

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Canadian Journal of Diabetes journal homepage: www.canadianjournalofdiabetes.com

Original Research

The Alberta’s Caring for Diabetes (ABCD) Study: Rationale, Design and Baseline Characteristics of a Prospective Cohort of Adults with Type 2 Diabetes Fatima Al Sayah PhD a, Sumit R. Majumdar MD b, Allison Soprovich MPH a, Lisa Wozniak MA a, Steven T. Johnson PhD c, Weiyu Qiu MSc a, Sandra Rees BScPharm a, Jeffrey A. Johnson PhD a, * a

Alliance for Canadian Health Outcomes Research in Diabetes, School of Public Health, University of Alberta, Alberta, Canada Faculty of Medicine, University of Alberta, Alberta, Canada c Centre for Nursing and Health Studies, Athabasca University, Alberta, Canada b

a r t i c l e i n f o

a b s t r a c t

Article history: Received 2 October 2014 Received in revised form 20 April 2015 Accepted 1 May 2015 Available online xxx

Objective: To better understand the factors that affect care and outcomes in patients with type 2 diabetes, we developed the prospective Alberta’s Caring for Diabetes (ABCD) cohort to collect, monitor and analyze data concerning several sociodemographic, behavioural, psychosocial, clinical and physiological factors that might influence diabetes care and outcomes. Methods: We recruited 2040 individuals with type 2 diabetes through primary care networks, diabetes clinics and public advertisements. Data are being collected through self-administered surveys, including standardized measures of health status and self-care behaviours, and will eventually be linked to laboratory and administrative healthcare data and other novel databases. Results: The average age of respondents was 64.4 years (SD¼10.7); 45% were female, and 91% were white, with average duration of diabetes of 12 years (SD¼10.0). The majority (76%) were physically inactive, and 10% were smokers. Most (88%) reported 2 or more chronic conditions in addition to diabetes, and 18% screened positively for depressive symptoms. The majority (92%) consented to future linkage with administrative data. Based on the literature and comparison with other surveys, the cohort appeared to fairly represent the general Alberta population with diabetes. Conclusions: The ABCD cohort will serve as the basis for explorations of the multidimensional and dynamic nature of diabetes care and complications. These data will contribute to broader scientific literature and will also help to identify local benchmarks and targets for intervention strategies, helping to guide policies and resource allocation related to the care and management of patients with type 2 diabetes in Alberta, Canada. Ó 2015 Canadian Diabetes Association

Keywords: complications health outcomes prospective cohort surveillance type 2 diabetes

r é s u m é Mots clés : complications résultats cliniques cohorte prospective surveillance diabète de type 2

Objectif : Pour mieux comprendre les facteurs qui influent sur les soins et les résultats cliniques des patients souffrant du diabète de type 2, nous avons créé la cohorte prospective Alberta’s Caring for Diabetes (ABCD), surveiller et analyser les données de plusieurs facteurs sociodémographiques, comportementaux, psychosociaux, cliniques et physiologiques qui influenceraient les soins aux diabétiques et les résultats cliniques. Méthodes : Nous avons recruté 2040 individus souffrant du diabète de type 2 par le biais des réseaux de soins primaires, les cliniques de diabète et les annonces publiques. Les données sont actuellement recueillies au moyen d’enquêtes autoadministrées, dont les mesures standardisées de l’état de santé et des comportements de prise en charge personnelle des soins, et seront par la suite liées aux données sur les soins de santé administratives et de laboratoire, et aux autres nouvelles bases de données. Résultats : Chez les répondants dont l’âge moyen était de 64,4 ans (ÉT 10,7), 45 % étaient de sexe féminin et 91% étaient blancs, et ils avaient le diabète en moyenne depuis 12 ans (ÉT 10,0). La majorité (76 %) était inactive physiquement, puis 10 % étaient des fumeurs. La plupart (88 %) rapportaient 2 maladies

* Address for correspondence: Jeffrey A. Johnson, PhD, Department of Public Health Sciences, 2-040 Li KaShing Centre for Health Research Innovation, University of Alberta, Edmonton, Alberta T6G 2E1, Canada. E-mail address: [email protected] 1499-2671/$ e see front matter Ó 2015 Canadian Diabetes Association http://dx.doi.org/10.1016/j.jcjd.2015.05.005

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chroniques ou plus en plus du diabète, puis 18 % obtenaient un résultat positif au dépistage des symptômes de dépression. La majorité (92 %) consentait à l’appariement futur aux données administratives. Selon la littérature et la comparaison à d’autres enquêtes, la cohorte semblait assez bien représenter la population générale de l’Alberta souffrant de diabète. Conclusions : La cohorte ABCD servira de base aux explorations de nature multidimensionnelle et dynamique des soins aux diabétiques et des complications. Ces données contribueront à enrichir la littérature scientifique et aideront également à déterminer les cibles et les repères locaux des stratégies d’intervention, qui faciliteront l’orientation des politiques et l’allocation des ressources liées aux soins et à la prise en charge des patients souffrant du diabète de type 2 de l’Alberta, au Canada. Ó 2015 Canadian Diabetes Association

Introduction Diabetes currently affects approximately 1.9 million Canadians (1) and is the seventh leading cause of death in Canada (2), shortening life expectancy by up to 15 years (3). The debilitating nature of diabetes results from its association with many comorbidities and increased risk for complications. People with diabetes are twice as likely to suffer heart attacks and stroke, 2.5 times more likely to develop heart failure, 10 to 15 times more likely to develop end stage renal disease, and 15 times more likely to have lower-limb amputation than people without diabetes (2). In addition to these complications, mental health disorders are common in people with diabetes. Depression, for example, is present in 20% of those with diabetes in community settings and in 32% of patients with diabetes in clinical settings, (4) and is significantly associated with other diabetes-related complications and higher mortality risk (5,6). The accumulation of comorbidities and complications in people with diabetes is associated with significant reductions in functional health status (7,8) and health-related quality of life (9,10), with the largest deficits being observed in the cases of stroke and depression (11). In addition to the morbidity and mortality, diabetes takes a major economic toll. Total healthcare costs for diabetes in Canada were estimated to be $4.66 billion in 2000 and are projected to increase to more than $8.14 billion by 2016 (12); the management of long-term complications and hospitalizations are the biggest drivers of these costs (13). The medical management of diabetes is complex and multifaceted, requiring a substantial degree of patient self-care and management in concert with quality healthcare (14). A key component of improving the management of the health of people with diabetes is the continuous assessment of their healthcare and outcomes. In Canada, the National Diabetes Surveillance System uses administrative claims data and aims to document the burden of diabetes in Canada through ongoing observation. In Alberta, such analysis has been done by the Alberta Diabetes Surveillance System (ADSS), which also uses administrative data. These types of data, in Canada and elsewhere, are, by nature, limited in terms of quality and completeness of scope and comprehensiveness of measurements. For that, several cohort studies of the natural history of people with type 2 diabetes have been undertaken in a few countries, including the United States (15,16) and Australia (17,18), and have collected data over years concerning sociodemographic, behavioural, psychosocial and clinical factors, which have yielded important and novel information about improving diabetes care and management. We are unaware, however, of any similar longitudinal studies of people with diabetes in Canada, where epidemiologic studies have typically used population-level data available through administrative health records (19e21). We, therefore, established the prospective Alberta’s Caring for Diabetes (ABCD) cohort to comprehensively measure and study many aspects of diabetes management and health outcomes in the Canadian context. The overarching purpose of the ABCD cohort study is to better

understand the factors that affect health outcomes in patients with type 2 diabetes; the specific objectives are: 1. To characterize and monitor the health status, clinical management and self-care behaviours of the population with type 2 diabetes in Alberta 2. To examine and monitor several aspects of diabetes care and management and their effects on a wide range of health outcomes in patients with type 2 diabetes 3. To provide a sampling frame for multiple controlled trials of quality-improvement interventions.

Methods Study design, eligibility and recruitment We established a prospective cohort of patients with type 2 diabetes in Alberta. Data are being collected initially via mailed, self-administered questionnaires, with follow-up measurements on an annual basis for the first 3 years and biannually thereafter. Patients with type 2 diabetes older than 18 years of age and able to communicate in English were eligible to participate. Patients who have type 1 or gestational diabetes were excluded. Our goal was to recruit approximately 1% of the population with type 2 diabetes in the province (22). Patients with type 2 diabetes residing within the 5 health zones (North, Edmonton, Central, Calgary and South) that make up the entire Alberta population were targeted for recruitment. Participants were recruited over a 2-year period (December 2011 to December 2013) using several approaches and strategies. Posters and brochures were displayed at family physicians’ and endocrinologists’ offices, diabetes clinics and community pharmacies throughout the province. Potential participants were also actively recruited through newspaper, radio and television advertisements. Additionally, patients in diabetes registries at primary care networks and other diabetes clinics were identified and invited to participate in the study. Eligible participants who expressed interest in participating were mailed self-administered surveys. Reminder postcards were mailed approximately 4 weeks after the initial mail-out for participants who had not returned the survey. No further follow-up was planned for nonrespondents after this reminder. All participants provided written consent for the survey and were asked to provide their personal health number (PHN) and separate consent for data-linkage. The study was approved by the health research ethics board at the University of Alberta (reference # Pro00016667). Self-reported (survey) measures We developed this cohort study to measure and examine a wide range of medical, behavioural and psychosocial factors known or hypothesized to be confounding, modifying or mediating factors associated with the development of

F. Al Sayah et al. / Can J Diabetes xxx (2015) 1e7

complications and other outcomes in patients with type 2 diabetes. The survey included a variety of items, measures and standardized scales that had been developed previously, validated and applied in diabetes population surveys. After data collection for year 1 was completed, we identified additional variables that were considered important to characterize in this population and, accordingly, modifications were made to the survey of year 3 assessments (Appendices 1 and 2 include both versions of the survey). The following items and measures were included in the surveys (Table 1):  Diabetes-related variables, including diabetes duration, family history, comorbidities, complications and hypoglycemic episodes  Disease management, including self-care, medication use, general and cost-related medication adherence, and readiness to change dietary behaviours and physical activity  Health and lifestyle variables, including smoking status, alcohol consumption, substance use, influenza and pneumococcal vaccinations, self-reported height and weight, physical activity, sitting time and sleep patterns and problems

 Health-related quality of life, including functional health and preference-based health status  Emotional and psychosocial well-being, including depressive symptoms, diabetes-related distress, anxiety, and chronic pain  Self-confidence and abilities, including self-efficacy, health literacy and numeracy  Quality of care, including clinical monitoring (A1C, cholesterol, eye exam, blood pressure, kidney function, foot care, waist circumference, weight), and satisfaction with general healthcare services, with personal doctor and specialist care, and with general medical care  Sociodemographics, including age, sex, marital status, educational level, employment status, ethnicity, and total household income. Linkage to laboratory and administrative data Survey data will be linked to data from Alberta Health to assess past and future healthcare utilization and clinical outcomes, using PHNs provided by participants. Administrative data will include the number of visits to general practitioners and

Table 1 Summary of main variables collected Section

Examples of variables

Measures and standardized scales

Disease-related variables

Diabetes duration Family history of diabetes Comorbidities Diabetes complications Hypoglycemic episodes Self-care management (diet, self-monitoring of blood glucose, foot care, medications) Medication use General medication non-adherencey Cost-related medication non-adherencey

Derived from the PHAC-SLCDC survey (25)

Disease management

Health and lifestyle variables

Quality of life Emotional and psychosocial well-being

Self-confidence and abilities

Quality of care

Sociodemographics Healthcare utilization

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Readiness to change: diety Readiness to change: physical activityy Smoking status Alcohol consumption Substance use Height, weighty Physical activity Sitting timey Sleep patterns and problemsy Vaccination status (influenza, pneumococcal) Functional health status Health-related quality of life Depressive symptoms Diabetes-specific stress* Anxietyy Chronic painy Self-efficacy Health literacy* Numeracyy Clinical monitoring by healthcare professional (A1C, cholesterol levels, eye exam, blood pressure, kidney function, feet, waist circumference, weight) Satisfaction with general healthcare services* Satisfaction with personal doctor care* Satisfaction with specialist care* Satisfaction with medical care Age, sex, marital status, educational level, employment status, ethnicity, total household income Number of general practitioner visits Number of specialist visits Number of ER visits Number of hospitalizations

Summary of Diabetes Self-Care Activities (SDSCA) (34) Derived from the PHAC-SLCDC survey (25) Self-rating single-item general medication adherence scale (35) Self-rating single-item cost-related medication adherence scale (35) Transtheoretical Model Stage’s Measure (36) Derived from the PHAC-SLCDC survey (25) 3 questions to detect hazardous drinking (37) Derived from the PHAC-SLCDC survey (25) Derived from the PHAC-SLCDC survey (25) Godin-Shephard Leisure-Time Physical Activity Questionnaire (38) International physical activity questionnaire (IPAQ) (39) Derived from the NHANES survey (40) Derived from the PHAC-SLCDC survey (25) SF-12 version 2 (41) Euroqol EQ-5D-5L (42) Patient Health Questionnaire 8-items (PHQ-8) (24) Problem Areas in Diabetes-5 items (PAID-5) (43) Generalized Anxiety Disorder 2-item scale (GAD-2) (44) Chronic Pain Scale (45) Self-Efficacy for Managing Chronic Disease 6-items (SEMCD-6) (46) 3-brief screening questions of inadequate health literacy (47) Subjective Numeracy Scale 4-items (SNS-4) (48) Derived from the PHAC-SLCDC survey (25)

Consumer Assessment of Healthcare Providers and Systems Health Plan Survey (CAHPS) (49) Patient Satisfaction Questionnaire: 2 items (PSQ-2) (50) Derived from the PHAC-SLCDC survey (25) Linkage to administrative data

NHANES, National Health and Nutrition Examination Survey; PHAC-SLCDC, Public Health Agency of Canada: Survey of Living with Chronic Diseases in Canada. * Years 1 and 2 only. y Added in year 3.

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specialists, the number of emergency room visits, and the number of hospitalizations and lengths of stay (Table 1). Similarly, PHNs will be used to link with laboratory data through the Data Integration, Measurement and Reporting unit within Alberta Health Services, and all data linkages will be de-identified. In the future, it may also be possible to link individuals with electronic medical records as well as with the provincial pharmacy databases. Data management and analysis Each survey was entered by 2 individuals into the online database; then the double-entered data were exported and checked using a statistical software package, and discrepancies were manually verified and corrected against original paper-based surveys, if necessary. Hard copies of surveys are kept in locked cabinets in the study office. Scoring standardized scales within the survey and dealing with missing data on items of these scales are done according to developer instructions. Descriptive statistics are calculated for all variables, and the final methods of data analyses will be project based. Minimum adjustment will include age, sex, region and recruitment method. Weights to adjust for over- and under-sampling will also be applied when appropriate. The data analysis for this paper was generated using SAS software v 9.4 (SAS Institute, Cary, North Carolina) (23).

Results Our recruitment strategies yielded a sample of 2040 participants, with over 95% providing their PHNs and consent for linkage with administrative data. The majority of participants (67%) were recruited through diabetes clinics and primary care networks, and the remaining (33%) through advertising. The cohort distribution across the provincial health zones was similar to the prevalence of diabetes reported in the ADSS (22), with 37% from the Edmonton zone, 32% from the Calgary zone, 21% from the Central zone, 7% from the North zone and 3% from the South zone. Sociodemographic and lifestyle characteristics The average age of respondents was 64.4 years (SD 10.7), 45% were female, 91% were white, 14% had less than high school education, 57% were unemployed/retired, 29% were in the lowest income category (<$40,000), and 63% reported a family history of diabetes (Table 2). The majority (76%) of participants were considered physically inactive, and 10% were current smokers. The average diabetes duration was 12 years, with over one-third of participants reporting having had diabetes for 10 years or more. Of the participants, 63% reported to have received the influenza vaccination in the past year, and 53% had received the pneumococcal vaccine in their lifetimes. Medical characteristics The average number of comorbidities, based on 16 potential conditions (heart disease; cerebrovascular disease; hypertension; hyperlipidemia; obesity; respiratory disorders; thyroid problems; cancer; mental, psychological or behavioral disorders; chronic pain; sleep disorders; neurologic disorders; musculoskeletal or rheumatic disorders; gastrointestinal disorders; eye diseases and renal diseases) reported was 4 (SD¼2.3), ranging from 0 to 13 conditions. Of the participants, 88% reported having 2 or more chronic conditions in addition to diabetes (Table 3). Hyperlipidemia (68%), obesity (54%) and musculoskeletal or rheumatic

Table 2 Baseline sociodemographic and lifestyle characteristics of cohort participants (year 1) and SLCDC participants with diabetes Characteristic

ABCD cohort (n¼2040) mean  SD or n (%y)

SLCDC* (26) (n¼2682) mean  SD or n (%y)

Age, years 20 to 44 45 to 64 65 Female sex Education Less than high school Completed high school Higher than high school Unemployed/retired Ethnicity White Aboriginal Others Annual household income <$40,000 $40,000 to $80,000 $80,000 Positive family history of diabetes Smoking: current Alcohol consumption: current Physical inactivityz Diabetes duration <2 years 3 to 5 years 6 to 9 years 10 Flu vaccine: yes Pneumococcal vaccine: yes

64.4  10.7 81 (4.0) 958 (47.0) 949 (46.5) 917 (45.0)

63.4  20.7 118 (6.6) 1003 (45.7) 1561 (47.6) 1338 (41.9)

276 (13.5) 813 (39.9)

613 (14.6) 371 (12.3)

939 (46.0)

1635 (73.2)

1167 (57.2)

d

1852 (90.8) 48 (2.4) 109 (5.3)

2428 (81.0) 101 (3.3) 142 (15.7)

583 596 485 1280

(28.6) (29.2) (23.8) (62.8)

d d d d

213 (10.4) 1418 (69.5)

d d

1557 (76.3) 12.3  10.0 223 (10.3) 256 (12.5) 290 (14.2) 797 (39.1) 1287 (63.1) 1090 (53.4)

d d 396 549 460 1258 d d

(15.4) (21.9) (17.9) (44.9)

ABCD, Alberta’s Caring for Diabetes study; SLCDC, Survey of Living with Chronic Diseases in Canada. * Data on some of the demographic variables were not available for the SLCDC sample. y Percentages do not add up to 100% due to missing data. z <150 minutes/week of moderate and vigorous physical activity.

disorders (50%) were the most common comorbidities in this cohort at baseline. Psychosocial characteristics and health status The mean depressive symptoms score was 5.2 (SD¼5.4), with 18% of participants reporting moderate to severe symptoms (24) (Table 3). Participants generally reported low diabetes-related distress, with a mean score of 0.85 (SD¼0.87), and 13.4% reported current distress. The mean self-efficacy score was 7.5 (SD¼2.3), with 64% reporting high levels, and the mean health literacy score was 5.3 (SD¼2.7), with 83% having adequate skills. Participants generally reported high scores on all health-related quality of life measures, with a mean EQ-5D-5L index score of 0.8 (SD¼0.15), a mean Physical Component Summary (PCS) score of 44.4 (SD¼10.8), and a mean Mental Component Summary (MCS) score of 48.1 (SD¼9.9). Diabetes management In general, self-care management was low for all skills except for medications (6.3 days/week); of all of the self-care activities, the least frequently performed was foot care (3.9 days/week) (Table 3). Clinical monitoring by care providers was generally high for almost all tasks, except for diabetic foot check and waist circumference measurement.

F. Al Sayah et al. / Can J Diabetes xxx (2015) 1e7 Table 3 Baseline medical, behavioural, psychosocial and health characteristics of cohort participants (year 1) Characteristic Comorbidities (self-reported) Heart disease Cerebrovascular disease Hypertension Hyperlipidemia Obesity Respiratory diseases Thyroid disorders Cancer Mental, psychological or behavioural disorders Chronic pain Sleep disorders Neurologic disorders Musculoskeletal and rheumatic disorders Gastrointestinal disorders Eye diseases Renal diseases Number of comorbidities reported 0 1 2 Depressive symptoms score (0-24) Level No (0 to 5) Mild (6 to 9) Moderate (10 to 14) Moderate-severe (15 to 19) Severe (20) Diabetes distress score (0 to 4) Level: present Self-efficacy score (0 to 10) Level Low (0 to 3) Medium (4 to 6) High (7 to 10) Health literacy score (3 to 15) Level ; adequate (<9) Quality of life EQ-5D-5L index score SF-12 PCS SF-12 MCS Self-care management General diet (0 to 7 days) Specific diet (0 to 7 days) Self-monitoring of blood glucose (0-7 days) Foot care (0 to 7 days) Medications (0 to 7 days) Clinical monitoring by healthcare professional (past year) Checked blood pressure at most diabetes appointments Checked feet for sores or irritations Checked feeling in the feet Tested urine to check kidney function Tested blood to check kidney function Measured waist circumference Measured weight

n¼2040 mean  SD or n (%*) 387 (19.0) 641 (31.4) 861 (42.2) 1392 (68.2) 1099 (53.9) 375 (18.4) 432 (21.2) 275 (13.5) 247 (12.1) 33 (1.6) 38 (1.9) 394 (19.3) 1011 (49.6) 60 (2.9) 709 (34.8) 374 (18.3) 4.1  2.3 64 (3.1) 173 (8.5) 1803 (88.4) 5.2  5.4 1162 (57.0) 458 (22.5) 204 (10.0) 113 (5.5) 55 (2.7) 0.85  0.87 269 (13.4) 7.5  2.3 184 (9.0) 431 (21.1) 1312 (64.3) 5.3  2.7 1686 (82.7) 0.80  0.17 44.4  10.8 48.1  9.9 4.7 4.2 4.1 3.9 6.3

    

2.0 1.6 2.6 1.7 1.8

1738 (90.1) 844 699 1542 1427 471 1503

(41.4) (34.3) (75.6) (70.0) (23.1) (73.7)

EQ-5D-5L, A 5-level European Quality of life questionnaire-5 dimensions; MCS, mental composite summary score; PCS, physical composite summary score. * Percentages do not add up to 100% due to missing data.

Cohort representativeness and generalizability In order to examine the representativeness of the ABCD cohort, we compared participants in this study to a sample of 2682 patients with type 2 diabetes from the 2011 Survey for Living with Chronic Diseases in Canada (SLCDC) (25,26). ABCD cohort participants were of similar age, sex and diabetes duration but were more likely to be white and less educated compared to the SLCDC sample (Table 2). We also compared the ABCD cohort participants to a sample of 380

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patients with diabetes in Alberta from the 2012 Health Quality Council of Alberta (HQCA) survey (27). ABCD cohort participants were slightly older, more likely to be white, had distribution similar to that of the HQCA sample across income categories but better representative distribution across education levels (Table 4). Further, in terms of age and sex distribution, the ABCD cohort is comparable to that of the 2011 Alberta Diabetes Atlas, which reported that most cases of diabetes in Alberta occur in people between the ages of 60 and 64, with cases in males being the most prevalent (22). Further, the findings of several analyses that would emerge from this study may be transferable to other primary care settings in Canada, given their similarities in terms of organizational structure, multidisciplinary teams and focus on chronic conditions, among other characteristics (28), as well as to other primary care models in other countries such as the medical home in the United States (29). Discussion This article discusses the study rationale and procedures for the ABCD cohort and reports the baseline characteristics of 2040 people with type 2 diabetes in the province of Alberta. In establishing this cohort, we have created the foundation for a surveillance system for patient-reported outcome measures, lifestyle and selfcare behaviours, as well as quality of healthcare from the patients’ perspectives, for the province of Alberta. In terms of diabetes characteristics, the sample is reasonably representative of the population with type 2 diabetes and is consistent with estimates by the ADSS (22). With this preliminary description, we have also made several observations that warrant further research, including low self-care management in all areas, low clinical monitoring rates for diabetic foot problems, vaccination rates higher than those of the general population, high prevalence of comorbidities and diabetes-related complications, including depressive symptoms and health-related quality-of-life measurements. A key advantage of this cohort is the potential to link selfreported data to provincial administrative and laboratory data to help infer trends in diabetes care and health-seeking behaviours over time and link them with healthcare utilization and clinical outcomes. The longitudinal nature of the data will allow us to examine the temporal relationships among several factors and outcomes measured in this population, particularly the Table 4 Comparison between ABCD cohort participants and patients with diabetes from the HQCA survey Characteristic Sociodemographics Age, years 18 to 24 25 to 44 45 to 64 65 Female sex Educational level No formal schooling Completed grade school Completed high school or more Annual household income <$60,000 $60,000 to $100,000 $100,000 Ethnicity White Nonwhite

ABCD cohort (n¼2040) mean  SD or n (%)

HQCA study (n¼380) mean  SD or n (%)

64.4  10.7 2 (0.1) 79 (3.9) 958 (47.0) 949 (46.5) 917 (45.0)

60.0  13.9 6 (1.6) 47 (12.4) 188 (49.5) 139 (36.6) 175 (46.1)

276 (13.5) 813 (39.9) 939 (46.0)

80 (21.1) 82 (21.6) 218 (57.4)

925 (45.3) 432 (21.2) 307 (15.1)

188 (49.5) 81 (21.3) 63 (16.6)

1852 (90.8) 147 (7.2)

324 (85.3) 56 (14.7)

ABCD, Alberta’s Caring for Diabetes study; HQCA, Health Quality Council of Alberta.

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development and progression of diabetes-related complications. In addition, with more than 95% of participants’ providing consent for the linkage, we will retain the representativeness of the sample and considerable power in subsequent evaluations of use and outcomes. Additionally, this cohort has served (and will continue to serve) as a sampling scheme for quality-improvement trials, 2 of which have already been completed: 1) TeamCare, a collaborative primary care intervention for patients with type 2 diabetes and comorbid depression (30), and 2) Healthy Eating and Active Living for Diabetes (HEALD), an exercise specialist-led, walking-based lifestyle intervention for patients with type 2 diabetes (31). These 2 trials have yielded promising results that will improve diabetes care in Alberta. For example, the TeamCare trial showed that in patients with type 2 diabetes who screened positive for depressive symptoms, collaborative care improved depressive symptoms, but physician notification and follow up were also a clinically effective initial strategy compared with true usual care for these patients in Alberta (i.e. patients enrolled in this ABCD cohort) (32). These results, in addition to an evaluation of the implementation of these interventions (33), as well as their cost-effectiveness, have been shared and discussed with the local health authorities to inform decision making, particularly around potential policies concerning screening for depression in people with diabetes. We see great potential for ongoing and future substudies that might entail additional survey information (e.g. food-frequency questionnaires), physical activity measures (e.g. accelerometers) and even laboratory measurements (e.g. point-of-care glycated hemoglobin levels). Despite several strengths, including its size and novelty, this cohort has important limitations. First, although we use standardized scales and questionnaires that provide reliable measurements of the assessed variables in this cohort, there are inherent limitations in self-report surveys, and they vary by outcome measured. Nonetheless, we reviewed the psychometric properties of the available measurement tools of each of the measured variables and selected those previously reported as valid and reliable. As noted above, we revised the survey in subsequent years, allowing us to capture other key variables not included in the initial measurements. Second, although the use of a variety of recruitment approaches seems to have yielded a representative sample of people with type 2 diabetes from differing age, sex and sociodemographic groups, there may be an over-representation of those from the Central health zone and an under-representation of those from the South and North health zones. Further, these smaller numbers may limit our ability to compare results across all of the health zones. Third, this cohort under-represents non-white minorities, particularly immigrant and Aboriginal populations. This is unfortunate because these groups have high rates of diabetes and a greater burden of complications. Finally, because we intended to focus on the adult population with type 2 diabetes, which represents over 95% of the population with diabetes, we will not have any data with respect to children or to those with gestational or type 1 diabetes. Conclusion We conclude that, given the increasing prevalence of diabetes, its impact on morbidity and mortality and its high human and economic toll, it is crucial to study various aspects of diabetes and its management and to identify key targets for intervention strategies. For this reason, we recruited a cohort of more than 2000 patients with type 2 diabetes, who will be followed on an ongoing basis through self-administered surveys and linked administrative data. The data collected will be the basis for several explorations of the multidimensional nature of diabetes and its management and,

in turn, this information will provide both generalizable knowledge that will contribute to the scientific literature and will help to guide and inform health policies and resource allocation relating to the care and management of patients with type 2 diabetes in Alberta.

Acknowledgments JAJ is a Senior Scholar with Alberta Innovates-Health Solutions (AIHS) and a Centennial Professor at the University of Alberta. SRM is a Health Scholar funded by AIHS and holds the Endowed Chair in Patient Health Management funded by the Faculties of Medicine and Dentistry and Pharmacy and Pharmaceutical Sciences of the University of Alberta. This work was supported in part by grant from Alberta Health, and a CIHR Team Grant to the Alliance for Canadian Health Outcomes Research in Diabetes (#OTG- 88588), sponsored by the CIHR Institute of Nutrition, Metabolism and Diabetes (INMD).The authors thank Ana Mladenovic for reviewing and editing an earlier draft of this manuscript.

Author Contributions JAJ and SRM conceived the study, and all authors contributed to the design and implementation of the study. FAS drafted the manuscript, and all authors provided critical comments and revisions.

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