University of Alberta Determinants and Consequences of Childhood Overweight in Canada by Stefan Kuhle A thesis submitted to the Faculty of Graduate Studies and Research in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Public Health Department of Public Health Sciences c Stefan Kuhle Fall 2011 Edmonton, Alberta Permission is hereby granted to the University of Alberta Libraries to reproduce single copies of this thesis and to lend or sell such copies for private, scholarly or scientific research purposes only. Where the thesis is converted to, or otherwise made available in digital form, the University of Alberta will advise potential users of the thesis of these terms. The author reserves all other publication and other rights in association with the copyright in the thesis and, except as herein before provided, neither the thesis nor any substantial portion thereof may be printed or otherwise reproduced in any material form whatsoever without the author’s prior written permission. Abstract The prevalence of childhood obesity has increased dramatically over the last three decades in Canada with substantial consequences for the physical, mental, and economic wellbeing of the population. The overarching objective of this thesis was to examine the various aspects of childhood obesity in Canada, from prevalence trends and risk factors to economic and medical consequences. A systematic review (Objective 1) showed that the prevalence of childhood obesity in Canada has tripled since 1980. Using a prediction model (Objective 2), I demonstrated that the prevalence of overweight and obesity will further increase by 10% over the next 15 years if current trends continue unabated. An analysis of a population-based survey data among Grade 5 students in Nova Scotia linked with a perinatal database (Objective 3) showed that perinatal factors (large-for-gestational age, maternal pre-pregnancy weight) play an important role in the development of childhood overweight. Calculating the population attributable risk fractions for these risk factors (Objective 4), I was able to show that excess screen time and maternal pre-pregnancy weight offer the largest potential for prevention. Our analysis of the health care costs associated with childhood obesity (Objective 5) found that the obese children incurred 21% higher costs than normal weight children. Using data from the Canadian Health Measures Survey (Objective 6) I showed that the higher health care use is paralleled by a more frequent use of prescription medications in obese compared to normal weight children. An analysis of the medical reasons for this cost differential (Objective 7) found that obese children had higher health care utilization for internalizing disorders, asthma, other respiratory disorders, obesity, and chronic adenoid/tonsil disorder. I was further able to show, for the first time, that childhood obesity is strongly associated with otitis media (Objective 8), one of the most frequent childhood disorders. In our analysis of the diagnostic properties of an ICD code for obesity for the detection of measured obesity (Objective 9), the sensitivity was 10%. Children correctly identified as obese by an ICD code had a higher BMI and higher health care utilization. Acknowledgement First and foremost, I am indebted to Dr. Paul Veugelers who has been my su- pervisor, mentor, and friend over the past couple of years: Paul, without your encouragement and support, I would be nowhere close to where I am now. I will miss our conversations on research, food, spirits, soccer, life in general, and every- thing! A very special thanks goes out to Dr. Sara Kirk for providing supervisory, logisti- cal, and moral support in and out of Halifax. I would also like to thank Dr. Arto Ohinmaa, whose insightful comments always provided a new perspective to my analyses and results. I wish to express my thanks to the examiners at my candidacy exam and thesis defense, Drs. Noreen Willows, Sentil Senthilselvan, Sangita Sharma, Jennifer Tay- lor, and Don Voaklander, for their time, commitment, and input. I thank wholeheartedly Dr. Alec Allen for his support surrounding the data linkage and perinatal analyses. Thanks are also due to the members of the Population Health Intervention Re- search Unit at the School of Public Health, University of Alberta (in particular Andrea Cliff who was always there to help and make things happen in the back- ground). You are a great team! I am grateful to Irene Wong and Dr. Chuck Humphrey from the Research Data Centre at the University of Alberta for their support with the Markov modeling project. I would also like to acknowledge Charmaine Cooke and Yan Wang from the Pop- ulation Health Research Unit, Dalhousie University, for their assistance with data provision and access, and Brian Hoyt for computer support at Dalhousie. Finally, I would like to extend my gratitude to the children and parents who par- ticipated in the 2003 Children’s Lifestyle and School Performance Study in Nova Scotia. Contents 1 Introduction 1 1.1 The prevalence of childhood overweight and obesity in Canada . .2 1.2 Measurement of overweight and obesity . .2 1.3 Risk Factors for Childhood Overweight and Obesity . .4 1.4 Obesity-Associated Health Problems . .5 1.5 Health Care Utilization and Economic Burden . .6 1.6 Objectives . .6 1.7 References . .9 2 The prevalence of childhood overweight and obesity in Canada between 1980 and 2010 15 2.1 Introduction . 15 2.2 Methods . 15 2.3 Results . 17 2.4 Discussion . 18 2.5 References . 21 2.6 Tables . 25 3 Forecasting the prevalence of overweight and obesity in Canada 29 3.1 Introduction . 29 3.2 Methods . 29 3.3 Results . 32 3.4 Discussion . 32 3.5 References . 36 3.6 Table . 39 3.7 Figures . 40 4 Perinatal and childhood risk factors for overweight in a provincial sample of Canadian Grade 5 students 44 4.1 Introduction . 44 4.2 Methods . 45 4.3 Results . 48 4.4 Discussion . 49 4.5 Conclusion . 52 4.6 References . 53 4.7 Tables . 58 5 Prevention potential of risk factors for childhood overweight 61 5.1 Introduction . 61 5.2 Methods . 61 5.3 Results . 64 5.4 Discussion . 64 5.5 Conclusion . 65 5.6 References . 66 5.7 Table . 69 6 Use and cost of health services among overweight and obese Cana- dian children 70 6.1 Introduction . 70 6.2 Methods . 71 6.3 Results . 74 6.4 Discussion . 74 6.5 References . 77 6.6 Tables . 80 6.7 Figures . 83 7 Medication use in normal weight and overweight children in a na- tionally representative sample of Canadian children 84 7.1 Introduction . 84 7.2 Methods . 85 7.3 Results . 87 7.4 Discussion . 87 7.5 References . 90 7.6 Tables . 93 8 Health care utilization from prevalent medical conditions in normal weight, overweight and obese children 97 8.1 Introduction . 97 8.2 Methods . 98 8.3 Results . 100 8.4 Discussion . 101 8.5 Conclusion . 102 8.6 References . 104 8.7 Tables . 106 9 The association between childhood obesity and otitis media 110 9.1 Introduction . 110 9.2 Methods . 110 9.3 Results . 113 9.4 Discussion . 113 9.5 References . 116 9.6 Tables . 119 10 Comparison of ICD code-based diagnosis of obesity with measured obesity in children and the implications for health care cost esti- mates 122 10.1 Introduction . 122 10.2 Methods . 123 10.3 Results . 125 10.4 Discussion . 125 10.5 References . 128 10.6 Table . 130 11 Discussion 131 11.1 References . 136 List of Tables 2.1 Characteristics of studies assessing the prevalence of overweight and obesity in Canadian children between 1980 and 2010. 26 2.2 Study characteristics and reported prevalences of overweight (incl. obesity) and obesity in Canadian children (2 to 5 years and 6 to 11 years) between 1980 and 2010. 27 2.3 Study characteristics and reported prevalence of overweight (incl. obesity) and obesity in Canadian children (12 to 17 years) between 1980 and 2010. 28 3.1 Modeled prevalences of weight status categories in Canada from 2006 to 2026 by age group. 39 4.1 Prevalences and associations of child, family/environment, and perinatal factors with overweight in Grade 5 students in the 2003 Children’s Lifestyle and School Performance Study. 59 4.2 Associations of child, family/environment, and perinatal factors with obesity in Grade 5 students in the 2003 Children’s Lifestyle and School Performance Study. 60 5.1 Prevalences, multivariable adjusted population attributable risk fractions and odds ratios for preventable risk factors of childhood overweight. 69 6.1 Health care cost and utilization in grade five students from the Canadian province of Nova Scotia by weight status and sociode- mographic factors. 81 6.2 Exponentiated linear regression coefficients and incidence rate ra- tios and their 95% confidence intervals for the association between weight status, gender, household income, household education, ge- ographic region with health service utilization. 82 7.1 Demographics and medication use by weight status. 93 7.2 Prescription drug use by sociodemographic factors. 94 7.3 Incidence rate ratios for taking medications in the last month. 95 7.4 The most commonly used medication types within each ATC do- main in normal weight and overweight/obese children. 96 8.1 Diagnosis groups used in the analysis and the corresponding ICD-9 codes and descriptions. 106 8.2 Physician visits between 2001 and 2006 for selected conditions in a cohort of Nova Scotia elementary school children. 107 8.3 Physician costs between 2001 and 2006 for selected conditions in a cohort of Nova Scotia elementary school children. 108 8.4 Odds Ratios and 95% confidence intervals for having one.