Constipation and Laxative Use in the Community Barry L. Werth Bachelor of Pharmacy (Honours) (University of Queensland) Master of Business Administration (Deakin University) A thesis submitted in fulfilment of the requirements for the degree of Doctor of Philosophy Susan Wakil School of Nursing and Midwifery Faculty of Medicine and Health The University of Sydney 2019 Dedication To the memory of Helen “Trean” Werth RN (1954 - 2013) who would have preferred the thesis title: “Constipation and Aperient Use in the Community” ii Table of Contents Statement of originality viii Publications and conference presentations arising from this research ix Authorship attribution statement x Acknowledgements xii Abstract xiv List of abbreviations xvii List of tables xviii List of figures xx List of appendices xxi Glossary of terms xxii Chapter 1: Introduction 1 1.1 Background 2 1.1.1 Constipation: Definition and classification 4 1.1.2 Prevalence of constipation in the community 6 1.1.3 Factors associated with constipation in population-based studies 6 1.1.4 Laxative use: Definition and classification 8 1.1.5 Prevalence of laxative use in the community 10 1.1.6 Characterisation of laxative use 10 1.2 Research aims and objectives 12 1.3 Thesis outline 12 1.4 Significance of this research 16 1.5 References 17 Chapter 2: Epidemiology of constipation in adults: why estimates of prevalence differ 25 2.1 Abstract 26 2.2 Introduction 27 2.3 Methods 29 2.4 Search results 30 2.5 Prevalence of constipation 31 iii 2.5.1 Prevalence estimates in general adult populations 31 2.5.2 Prevalence estimates in older adult populations 40 2.6 Why prevalence estimates differ 43 2.6.1 Country/region 43 2.6.2 Definition of constipation 43 2.6.3 Data collection method 45 2.6.4 Sample characteristics 46 2.7 Conclusion 47 2.8 References 49 Chapter 3: Defining constipation to estimate its prevalence in the community: results from a national survey 57 3.1 Abstract 58 3.2 Introduction 59 3.3 Methods 60 3.3.1 Study population 60 3.3.2 Constipation definitions 61 3.3.3 Sample size 63 3.3.4 Analysis 63 3.3.5 Ethics approval 64 3.4 Results 65 3.4.1 Study population 65 3.4.2 Prevalence 67 3.4.3 Performance of simple definitions 69 3.5 Discussion 71 3.6 Conclusion 74 3.7 References 75 Chapter 4: Chronic constipation in the community: a national survey of Australian adults 78 4.1 Abstract 79 4.2 Introduction 80 iv 4.3 Methods 81 4.3.1 Study design and population 81 4.3.2 Questionnaire design 81 4.3.3 Sample size 82 4.3.4 Analysis 82 4.3.5 Ethics approval 83 4.4 Results 83 4.4.1 Study population and prevalence of chronic constipation 83 4.4.2 Factors associated with chronic constipation 85 4.5 Discussion 89 4.5.1 Prevalence of chronic constipation 89 4.5.2 Factors associated with chronic constipation 89 4.5.3 Strengths and limitations 91 4.6 Conclusion 92 4.7 References 93 Chapter 5: Use of over-the-counter laxatives by community-dwelling adults to treat and prevent constipation: a national cross-sectional study 97 5.1 Abstract 98 5.2 Introduction 99 5.3 Methods 100 5.3.1 Study population and recruitment 100 5.3.2 Survey questionnaire 101 5.3.3 Sample size 102 5.3.4 Analysis 102 5.3.5 Ethics approval 102 5.4 Results 103 5.5 Discussion 110 5.5.1 Utilisation of laxatives 110 5.5.2 Healthcare professional recommendation of laxatives 112 5.5.3 Effectiveness of laxatives 113 v 5.5.4 Strengths and limitations 114 5.6 Conclusion 114 5.7 References 115 Chapter 6: Laxative use and self-reported constipation in a community-dwelling elderly population 119 6.1 Abstract 120 6.2 Introduction 121 6.3 Methods 122 6.3.1 Data source 122 6.3.2 Study population and inclusion criteria 122 6.3.3 Constipation 123 6.3.4 Medications and laxative use 123 6.3.5 Potential risk factors for constipation 123 6.3.6 Statistical analyses 124 6.3.7 Ethics approval 124 6.4 Results 124 6.4.1 Study population characteristics 124 6.4.2 Laxative use 126 6.4.3 Constipation prevalence and risk factors 128 6.5 Discussion 132 6.6 Conclusion 135 6.7 References 136 Chapter 7: A longitudinal study of constipation and laxative use in a community-dwelling elderly population 139 7.1 Abstract 140 7.2 Introduction 141 7.3 Methods 143 7.3.1 Data source 143 7.3.2 Study population 143 7.3.3 Self-reported constipation 144 vi 7.3.4 Medication use 144 7.3.5 Potential risk factors for constipation 144 7.3.6 Analysis 145 7.4 Results 145 7.4.1 Study population 145 7.4.2 Constipation 147 7.4.3 Laxative use 150 7.4.4 Constipation and laxative use 151 7.5 Discussion 151 7.5.1 Constipation 151 7.5.2 Laxative use 153 7.5.3 Limitations 154 7.6 Conclusion 156 7.7 References 157 Chapter 8: Discussion, conclusion & future research directions 161 8.1 Discussion 162 8.1.1 The prevalence of constipation and laxative use 162 8.1.2 Factors associated with constipation in the community 165 8.1.3 Characterisation of laxative use in the community 167 8.2 Strengths and limitations 170 8.3 Conclusion 171 8.4 Recommendations for future research 172 8.5 References 173 Appendices Appendix 1: Survey questionnaire 177 Appendix 2: Ethics approval letter 192 Appendix 3: Participant information statement 195 vii viii Publications and Conference Presentations Arising from this Research Publications: Publication 1: Werth, B.L., Williams, K.A., & Pont, L.G. (2015). A longitudinal study of constipation and laxative use in a community-dwelling elderly population. Archives of Gerontology & Geriatrics 60,418- 424. Publication 2: Werth, B.L., Williams, K.A., & Pont, L.G. (2017). Laxative use and self-reported constipation in a community-dwelling elderly population. Gastroenterology Nursing 40 (2), 134-141. Publication 3: Werth, B.L. (2019). Epidemiology of constipation in adults: Why estimates of prevalence differ. Journal of Epidemiological Research 5(1),37-49. Publication 4: Werth, B.L., Williams, K.A., Fisher, M.J. & Pont, L.G. (2019). Defining constipation to estimate its prevalence in the community: results from a national survey. BMC Gastroenterology 19, 75. Conference Presentations: Oral presentations: Werth, B. (2013): Constipation and laxative use in a community-based elderly population, The 12th National Conference of Emerging Researchers in Ageing, Sydney, 25-26th Nov, 2013. Poster presentations: Werth, B. (2012): A longitudinal study of constipation and laxative use in a community-dwelling elderly population, ASCEPT-APSA Joint Conference, Sydney, 2-5th Dec, 2012. Werth, B. (2015): Laxative use and constipation in community-dwelling adults in Australia, ASCEPT- APSA Joint Scientific Meeting, Hobart, 29th Nov – 2nd Dec, 2015. ix x xi Acknowledgements This thesis would not have been possible without the assistance of many people and I wish to acknowledge the contributions of each. Firstly, my supervisory team must be acknowledged for their patience, support and generous amounts of time. I thank Professor Kylie Williams, my original primary supervisor, for taking me on in 2010 and finding the funds for the survey. Kylie’s academic experience and knowledge were invaluable in assisting me every step of the way. I appreciated being challenged with my writing and thinking, and will forever remember to ask the “so what?” question. I thank Associate Professor Murray Fisher, a latecomer to the team, for his expert guidance, professional judgement and encouragement to continue over the past few years. Murray was always available when needed and always provided sage advice. I am indebted to Associate Professor Lisa Pont, my primary supervisor for the bulk of my candidature. Lisa stuck with me even though she moved faculties and universities three times during my candidature. Lisa provided expert advice and tuition in the academic world. I have learned so much from Lisa whose intelligence and knowledge were inspirational. Throughout my lengthy candidature some adversities were encountered in the form of family tragedies, and personal illness and injury. The understanding and support provided by all supervisors at these difficult times was very much appreciated. Beyond the supervisory team, I also acknowledge the contributions of several others. At the School of Nursing and Midwifery, the support and encouragement provided by Associate Professor Tom Buckley, Associate Professor Jenny Fraser and especially Sybèle Christopher were instrumental in getting me through to the end. The expert statistical assistance provided by Judith Fethney, Sydney Nursing School Biostatistician, was invaluable in the analysis of data. I am very grateful for the generous amounts of time, helpful advice and patience provided by Judith. Also, I acknowledge the assistance provided by Associate Professors Terry Bolin (UNSW), Danny Stiel (USyd) and Philip Dinning (UNSW and now Flinders University) in reviewing the survey questionnaire. xii I must acknowledge and thank two special people who supported me along the way. At the beginning of my candidature, my late wife Trean encouraged me to pursue my ambition and assisted with some early work based on her nursing experience. Over the past few years, my partner Jennifer has helped me by understanding the time commitment required, encouraging me to continue whenever I contemplated giving it away and generally supporting me in my PhD endeavours. Finally, as a candidate of mature age, I thank the University of Sydney for approving my candidature and allowing me to pursue this research.