Elevated blood pressure and hypertension in South Asian children: A mixed-methods analysis exploring associated factors and behavioural influences by Adeleke Fowokan MPH, University of Essex, 2013 BSc, University of Lagos, 2010 Thesis Submitted in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy in the Department of Biomedical Physiology and Kinesiology Faculty of Science © Adeleke Fowokan 2019 SIMON FRASER UNIVERSITY Fall 2019 Copyright in this work rests with the author. Please ensure that any reproduction or re-use is done in accordance with the relevant national copyright legislation. Approval Name: Adeleke Fowokan Degree: Doctor of Philosophy Title: Elevated blood pressure and hypertension in South Asian children: A mixed-methods analysis exploring associated factors and behavioural influences Examining Committee: Chair: Sam Doesburg Associate Professor Scott Lear Senior Supervisor Professor Miriam Rosin Supervisor Professor Charlotte Waddell Supervisor Professor Faculty of Health Sciences Zubin Punthakee Supervisor Associate Professor, McMaster University Scott Venners Internal Examiner Associate Professor Faculty of Health Sciences Namratha Kandula External Examiner Associate Professor Department of Medicine Feinberg School of Medicine, Northwestern University Date Defended/Approved: October 16, 2019 ii Ethics Statement iii Abstract The overarching objective of this PhD thesis was to develop a better understanding of how broad-based (physiological, lifestyle, social and cultural) factors, influence blood pressure (BP) in South Asian children in Canada. This was done using a mixed-methods approach that included: a systematic review which informed the direction of the study; multivariate regression analyses to estimate the correlates of BP and hypertension in South Asian children; receiver operating characteristics curve analysis to estimate the validity of adiposity metrics in estimating adverse risk of hypertension in South Asian children, including the appropriate risk thresholds; and semi-structured qualitative interviews to explore attitudes towards healthy behaviours in South Asian children and their parents. From the systematic review, I identified a range of physiological, social and lifestyle factors that were associated with elevated BP and hypertension in children. These variables were subsequently investigated in a sample of 762 South Asian children in Canada. The results suggested that for these children, physiological variables provided better explanatory capacity regarding the risk of elevated BP and hypertension than social or lifestyle factors. Age, sex, BMI z-score, heart rate and weight accounted for 30% of the variance of sBP z-score, while age, BMI z-score, heart rate and daily fast food intake accounted for 23% of the dBP z-score variance. The prevalence of hypertension was found to be high at 12%. The area under the curve (AUC) values for the adiposity measures for boys and girls ranged from 0.74–0.80, suggesting that the adiposity measures were fair in their ability to estimate hypertension risk. Yet, sex- stratified cut-offs associated with adverse risk of hypertension for South Asian boys and girls suggested that these children might be at high risk of hypertension at levels of adiposity considered normal. Last, my interview findings documented the range of influences on healthy behaviour in South Asian children and their parents including school, peer, social media and cultural dynamics. Taken as a whole, my thesis provides vital information for healthcare practitioners in identifying and treating at-risk South Asian children, and for public health practitioners and policymakers in informing the development of effective intervention strategies aimed at preventing hypertension and CVD risk in this population. Keywords: Hypertension; Blood pressure; South Asians; Children; Adiposity; Mixed- methods. iv Acknowledgements Firstly, I will like express my utmost gratitude to my primary supervisor, Dr. Scott Lear for his mentorship and support throughout the PhD as well as my other committee members, Dr. Charlotte Waddell, Dr. Zubin Punthakee and Dr. Miriam Rosin for their insightful input and comments during every stage of the thesis writing process. I could not have imagined a better constellation of erudites to guide me through the PhD process. Personally, I would like to profoundly thank my family for their love, support and investment throughout my academic journey and life in general. They are the most important people in my cosmos. Lastly, my sincere gratitude goes to the volunteers, research assistants and community members who participated in this research. v Table of Contents Approval ........................................................................................................................ ii Ethics Statement ............................................................................................................ iii Abstract .......................................................................................................................... iv Acknowledgements ......................................................................................................... v Table of Contents ........................................................................................................... vi List of Tables ................................................................................................................. x List of Figures .............................................................................................................. xi List of Acronyms ............................................................................................................ xii Glossary ........................................................................................................................ xiii Chapter 1. Introduction .............................................................................................. 1 1.1. Background ........................................................................................................... 1 1.2. South Asian Ethnicity and Blood Pressure ............................................................. 1 1.3. Definition of Hypertension in Children .................................................................... 2 1.4. Trends in Hypertension in Children ........................................................................ 3 1.5. Multifactorial Etiology of Elevated BP and Hypertension ........................................ 4 1.5.1. Contribution of Physiological Risk Factors to Elevated BP and Hypertension 4 1.5.2. Contribution of Behavioural Risk Factors to Elevated BP and Hypertension .. 5 1.5.3. Contribution of Social Risk Factors to Elevated BP and Hypertension ........... 6 1.6. Assessment of Obesity in Children ........................................................................ 7 1.7. Thesis Rationale .................................................................................................... 9 1.8. Thesis Objectives .................................................................................................. 9 1.8.1. Rationale for Chapter 2 ................................................................................ 10 1.8.2. Rationale for Chapter 3 ................................................................................ 10 1.8.3. Rationale for Chapter 4 ................................................................................ 11 1.8.4. Rationale for Chapter 5 ................................................................................ 11 1.9. References .......................................................................................................... 13 Chapter 2. Correlates of elevated blood pressure in healthy children: a systematic review .............................................................................................. 18 2.1. Introduction .......................................................................................................... 18 2.2. Methods .............................................................................................................. 19 2.2.1. Search strategy and selection ...................................................................... 19 Identification ................................................................................................................ 21 1.1. ................................................................................................................................ 21 Screening for Eligibility .............................................................................................. 21 Included ....................................................................................................................... 21 1.2. ................................................................................................................................ 21 2.2.2. Risk of Bias Assessment ............................................................................. 21 2.2.3. Data Abstraction .......................................................................................... 28 2.2.4. Level of Evidence ........................................................................................ 28 vi 2.2.5. Outcomes .................................................................................................... 28 2.3. Results ...............................................................................................................