Risk Factors for Diabetes Mellitus: a Comparative Analysis of Subpopulation Differences in a Large Canadian Sample
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RISK FACTORS FOR DIABETES MELLITUS: A COMPARATIVE ANALYSIS OF SUBPOPULATION DIFFERENCES IN A LARGE CANADIAN SAMPLE (Thesis format: Monograph) by Michael James Taylor Graduate Program in Epidemiology and Biostatistics A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science The School of Graduate and Postdoctoral Studies The University of Western Ontario London, Ontario, Canada © Michael James Taylor 2013 Abstract Objectives: Certain Canadian subpopulations observe numerous modifiable and non- modifiable risk factors for diabetes. This study compares immigrants and Aboriginals (First Nations, Inuit, and Métis) with Canada-born individuals at higher risks for diabetes, and deciphers the determinant differences between them. Methods: Pooled Canadian Community Health Survey data (2001-2010) were used. Time trends for diabetes within each subsample were calculated using individual survey year prevalence rates; diabetes diagnoses were self-reported (N=33,565). Various risk factors were also examined using logistic regression. Results: Diabetes prevalence rates significantly increased from 2001 to 2010 for each subpopulation, as well as the total sample: Canada-Born individuals (3.9% to 5.7%), Immigrants (5.0% to 8.5%), Aboriginals (5.4% to 7.4%), and Canadians overall (4.1% to 6.4%). Conclusions: All Canadians, regardless of risk, experienced and will continue to experience a rise in diabetes. Future diabetes research involving the impact of race, culture, and ethnicity in Canadian immigrants should be holistically explored. Keywords diabetes mellitus, type 2 diabetes, risk factor, ethnicity, race, culture, immigrant, healthy immigrant effect, acculturation, Aboriginal, First Nations, Inuit, Métis, Canadian Community Health Survey (CCHS), pooling ii Acknowledgments I would first like to thank Dr. Amardeep Thind for his unwavering encouragement and support throughout my time at the University of Western Ontario. From the very beginning, he has offered consistently helpful advice, reassurance, and enthusiasm. Dr. Thind has honed my research interests and changed my academic perspective for the better. He has taught me that skepticism is not the primary tenet of the academic; rather, that it is an effective tool to judge the methodological and experimental frameworks I will encounter throughout my future career. I would also like to thank Dr. Stewart Harris for his optimistic and supportive contributions to my research process. Dr. Harris has dependably posed new and exciting ways of examining pertinent literature, certain subpopulations, and has helped a great deal by ensuring that my current work will lead to a fruitful career in research. His clinical experience, diabetes research mastery, and overall wealth of knowledge has provided me with an invaluable perspective throughout the thesis process. In addition to my supervisory committee, I would like to thank Dr. Kathy Speechley for her support throughout my entire time in the Epidemiology and Biostatistics program. As Graduate Chair, and as a mentor, she has been an incredible source of encouragement, reason, and understanding. Lastly, I would like to thank my family for their continuing support of my academic and professional interests; especially my mother, who has inspired my passion for diabetes research. iii Table of Contents Abstract ............................................................................................................................... ii Acknowledgments .............................................................................................................. iii List of Tables ................................................................................................................... viii List of Figures ................................................................................................................... iix List of Appendices ............................................................................................................... x List of Abbreviations .......................................................................................................... xi Chapter 1 .............................................................................................................................. 1 1 Introduction .................................................................................................................... 1 1.1 Diabetes Mellitus .................................................................................................... 1 1.1.1 Impact as a Chronic Disease ............................................................................ 3 1.2 Immigrant Health .................................................................................................... 4 1.3 Aboriginal Health ................................................................................................... 5 1.4 Aim of the Present Study ........................................................................................ 7 Chapter 2 .............................................................................................................................. 9 2 Literature Review .......................................................................................................... 9 2.1 Modifiable Risk Factors for T2DM and Diabetes Related Complications ........... 10 2.2 Non-Modifiable Risk Factors for T2DM and Diabetes Related Complications... 16 2.2.1 The Definition of Ethnicity in Epidemiological Research ............................. 18 2.2.2 Ethnic Origin and Obesity ............................................................................. 19 2.2.3 Ethnic Origin and Insulin Resistance ............................................................. 20 2.2.4 Findings from Canada: Ethnic Origin and T2DM ......................................... 20 2.2.5 Findings from the United Kingdom: Ethnic Origin and T2DM .................... 21 2.2.6 Findings from the United States: Ethnic Origin and T2DM .......................... 22 2.2.7 The Thrifty Gene Effect ................................................................................. 23 2.3 Migration, Health, and Birth Origin ..................................................................... 25 2.3.1 The Healthy Immigrant Effect and Acculturation in North America ............ 26 iv 2.3.2 Potential Barriers to Immigrant Health, Diabetes Management, and Healthcare Utilization ................................................................................................ 29 2.4 T2DM in Immigrants and Migration in Canada ................................................... 31 2.5 Canadian Aboriginals: Unique Characteristics ..................................................... 33 2.5.1 Modifiable Risk Factors for T2DM in Canadian Aboriginals ....................... 34 2.5.2 Non-Modifiable Risk Factors for T2DM in Canadian Aboriginals ............... 36 2.5.3 Canadian Aboriginals: Diabetes Burden and Diabetes Related Complications ............................................................................................................ 37 2.6 Summary ............................................................................................................... 38 Chapter 3 ............................................................................................................................ 41 3 Objectives .................................................................................................................... 41 Chapter 4 ............................................................................................................................ 43 4 Methodology ................................................................................................................ 43 4.1 Data Source and Sampling Design ....................................................................... 43 4.2 Data Collection ..................................................................................................... 48 4.2.1 Nonresponse and Data Quality ...................................................................... 49 4.2.2 Self-Reporting Bias and Interview Mode Effects .......................................... 49 4.3 Weighting .............................................................................................................. 51 4.3.1 Area Frame Weight ........................................................................................ 51 4.3.2 Telephone Frame Weight ............................................................................... 52 4.3.3 Final Weight Integration ................................................................................ 52 4.4 Combining CCHS Cycles ..................................................................................... 53 4.5 CCHS Data Access ............................................................................................... 55 4.6 Outcome Variable and Total Sample .................................................................... 55 4.7 Conceptual Framework ......................................................................................... 56 4.8 Statistical Analyses ............................................................................................... 61 4.8.1 Objective One ................................................................................................ 62 4.8.2 Objective Two ................................................................................................ 63 Chapter 5 ...........................................................................................................................