Epidemiological modelling of type 2 diabetes in Saudi Arabia

346 Pages·2013·4.23 MB·English

Epidemiological modelling of type 2
diabetes in Saudi Arabia: predicted
trends and public health implications

Abdulkareem J. Al Quwaidhi

Thesis submitted in partial fulfilment of the
requirements of the degree of Doctor of Philosophy

Institute of Health and Society
Faculty of Medical Sciences
Newcastle University
2013
Abstract
Background: The Kingdom of Saudi Arabia faces one of the highest
prevalence rates of type 2 diabetes mellitus (T2DM) in the world. However,
there are no credible local data on the trends and future projections of the
disease, and the relevant international studies underestimated the true
prevalence rates. This thesis used epidemiological modelling to study the trends
in T2DM prevalence in Saudi Arabia, predicted its future levels, and quantified
the impact of reducing some risk factors on the disease prevalence trends.
Methods: This thesis developed and validated the “Saudi IMPACT Diabetes
Forecast Model”, which integrates data on the population, obesity and smoking
prevalence trends in Saudis aged ≥25 years to estimate the trends in T2DM
prevalence (1992-2022) using a Markov modelling approach. The model
considers different reasonable scenarios of future trends in obesity prevalence,
and incorporates a number of parameters to model the disease epidemiology.
These parameters include the estimated diabetes incidence, case-fatality, total
mortality, relative risk of diabetes if obese, and relative risk of diabetes if a
smoker. The model data inputs and parameters were obtained from different
sources, including local departments, medical literature and assumptions. The
model results were validated against local data from the STEPwise survey in
2005, and against the model of the Global Burden of Disease study, where the
model produced reasonably close results to both of these studies.
Results: The prevalence of T2DM among the Saudi population aged ≥25 years
was estimated to rise substantially during the 30-year period of 1992-2022 from
8.5% to 39.5%, assuming some levelling off of obesity trends (capping), or to
44.1%, assuming uncapped increasing obesity trends. In men, T2DM
prevalence was estimated to increase from 8.7% to 39.2% with capped obesity
trends, or to 41.3% with continuing linear increase in obesity trends. In women,
T2DM prevalence was estimated to increase from 8.2% to 39.8% with capping
of obesity trends, or to 47.7% without such a capping. The model showed that if
the trends in obesity start to decline by 10% in 12 years (2010-2022), a relative
reduction of 13% in diabetes prevalence could be achieved. If the prevalence of
obesity was halted at the 2010 levels, a 10% relative reduction in diabetes
prevalence could be attained by 2022.
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Conclusion: T2DM is currently a major public health challenge in Saudi Arabia,
and this thesis predicted that its burden will increase substantially in the next
decade. Intensive and aggressive preventive measures directed to reduce the
levels of risk factors, particularly obesity and smoking, can result in reasonable
reduction of the disease prevalence, and therefore should be an urgent action.

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Dedication
This piece of work is dedicated to:

my father, my mother,
my wife (Nora), my daughter (Dalia), and my son (Mohammed).

With my sincere thanks for your love, patience and support.
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Acknowledgements
I would never have been able to finish my PhD without the guidance of my
supervisory team, help from colleagues and friends, and support from my family
and wife.
I would like to express my deepest gratitude to my supervisors: Dr Mark Pearce,
Dr Eugene Sobngwi, Professor Julia Critchley, and Dr Martin O’Flaherty. Dr
Pearce kindly provided me with continuous support and guidance through the
frequent regular meetings. He taught me much about the proper ways of
literature review, critical appraisal, and the relevant epidemiological methods. Dr
Sobngwi helped me with understanding various aspects of the diabetes
epidemiology, particularly in developing countries. Professor Critchley
introduced me to the field of epidemiological modelling. She spent much time
training me on the IMPACT model, making comments on my written drafts, and
kindly established my working relationship with the developers of the model in
Liverpool. Dr O’Flaherty generously shared with me his broad knowledge and
skills in modelling through several constructive meetings in Liverpool, and
offered me unlimited teaching and support during all the stages of modelling
work.
I would like to thank Professor Simon Capewell, the principal developer of the
IMPACT model, for his great support and encouraging remarks and
suggestions. Also, many thanks to my assessors: Professor Richard Walker
and Dr Louise Hayes for evaluating my progress and for their valuable
comments.
Thanks to the Saudi Ministry of Health and the Saudi Cultural Bureau in London
for sponsoring/ funding my three-year PhD studies. I would also like to convey
warm thanks to all IHS staff and student colleagues. I will never forget their
invaluable cooperation, which created the lovely and friendly research
atmosphere.

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Many thanks and warm gratitude to my beloved parents, who constantly
supported me with sincere prayers and best wishes. I am also very grateful to
the continuous encouragement from my sisters, brothers, nephews, nieces and
friends.
Finally, I owe very exceptional thanks and gratitude to my wife (Nora), my
daughter (Dalia), and my son (Mohammed) for their love, patience, and endless
support for me to accomplish my studies successfully.
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Table of contents

Abstract ............................................................................................................ ii
Dedication ....................................................................................................... iv
Acknowledgements ......................................................................................... v
Table of contents ........................................................................................... vii
List of tables ................................................................................................. xiii
List of figures ................................................................................................. xx
List of abbreviations ................................................................................... xxvi
Chapter 1. Introduction ................................................................................... 1
1.1. Background ............................................................................................. 1
1.2. What is this thesis about? ........................................................................ 2
1.3. Why is this thesis important? ................................................................... 3
1.4. Why does this thesis use modelling? ....................................................... 4
1.5. Why does this thesis use only obesity and smoking as risk factors
for T2DM? ...................................................................................................... 6
1.6. The overall aim of this thesis ................................................................... 7
1.7. Specific objectives ................................................................................... 7
1.8. Overview of the chapters ......................................................................... 8
Chapter 2. Type 2 diabetes: diagnosis and risk factors.............................. 10
2.1. Diagnosis of type 2 diabetes (brief overview) ........................................ 10
2.1.1. Relevant definitions......................................................................... 10
2.1.2. Diagnostic criteria ........................................................................... 11
2.2. Risk factors for type 2 diabetes ............................................................. 15
2.2.1. Demographic risk factors ................................................................ 16
2.2.2. Genetic risk factors ......................................................................... 22
2.2.3. Behavioural and environmental risk factors ..................................... 24
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2.2.4. Role of modifying the behavioural/ environmental risk factors in
prevention of type 2 diabetes .................................................................... 43
Chapter 3. Size of the problem of type 2 diabetes in the world, developing
countries, and Saudi Arabia ......................................................................... 48
3.1. Global epidemiology of type 2 diabetes ................................................. 48
3.1.1. Background .................................................................................... 48
3.1.2. Global estimates and projections of type 2 diabetes prevalence ..... 49
3.2. Diabetes burden in developing countries ............................................... 55
3.3. Diabetes burden in the Eastern Mediterranean Region ......................... 56
3.4. Prevalence of diabetes, obesity and smoking in the countries of Gulf
Cooperation Council ..................................................................................... 58
3.4.1. Overview ......................................................................................... 58
3.4.2. Published studies on the prevalence of diabetes, obesity, and
smoking in the GCC countries .................................................................. 60
3.5. Prevalence of diabetes, obesity and smoking in Saudi Arabia ............... 65
3.5.1. Introduction ..................................................................................... 65
3.5.2. Demography ................................................................................... 66
3.5.3. Overview of the Saudi health care system ...................................... 69
3.5.4. Non-communicable diseases in Saudi Arabia ................................. 71
3.5.5. Diabetes health care in Saudi Arabia .............................................. 72
3.5.6. Published studies on the prevalence of type 2 diabetes, obesity and
smoking in Saudi Arabia ........................................................................... 75
Chapter 4. Epidemiological Modelling ......................................................... 83
4.1. What is a model?................................................................................... 83
4.2. What are the uses of models in epidemiology and public health? .......... 83
4.3. Why model type 2 diabetes? ................................................................. 84
4.4. Overview of Markov models .................................................................. 85
4.4.1. Background .................................................................................... 85
4.4.2. General structure of a Markov model .............................................. 86
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4.4.3. Limitations of Markov models .......................................................... 87
4.5. What are the steps of developing a model? ........................................... 88
4.6. Existing diabetes models in the literature .............................................. 93
4.6.1. Background .................................................................................... 93
4.6.2. Published diabetes models ............................................................. 93
Chapter 5. The Saudi IMPACT Diabetes Forecast Model: data inputs, data
sources, and methods ................................................................................. 107
5.1. Introduction ......................................................................................... 107
5.2. Structure of the Saudi IMPACT Diabetes Forecast Model software ..... 112
5.3. Data inputs into the Saudi IMPACT Diabetes Forecast Model:
description, sources and assumptions ........................................................ 117
5.3.1. Introduction ................................................................................... 117
5.3.2. Description of data inputs and their sources ................................. 118
5.4. Sensitivity analyses ............................................................................. 164
5.4.1. Analysis of extremes ..................................................................... 164
5.4.2. Modelling scenarios with capped versus uncapped projections in the
obesity trends ......................................................................................... 165
5.4.3. Modelling scenarios with inclusion versus exclusion of the two oldest
age groups of population ........................................................................ 166
Chapter 6. Past and current trends in the estimated prevalence of type 2
diabetes in Saudi Arabia ............................................................................. 167
6.1. Trends in the prevalence of type 2 diabetes in Saudi Arabia during
1992 - 2013 ................................................................................................ 167
6.1.1. The overall and sex-specific prevalence of diabetes and numbers of
diabetic individuals in the Saudi population ............................................. 168
6.1.2. Age- and sex-specific prevalence of diabetes and numbers of
diabetic individuals ................................................................................. 179
6.1.3. Quantified effects of the assumed capping of obesity on the
modelling results for 2013 ....................................................................... 192
6.2. Validation of the Saudi IMPACT Diabetes Forecast Model .................. 195
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6.2.1. Validation against local observed data .......................................... 195
6.2.2. Validation against another model .................................................. 198
Chapter 7. Using the Saudi IMPACT Diabetes Forecast Model to predict
the future trends in diabetes prevalence in Saudi Arabia ......................... 201
7.1. Trends in the prevalence of type 2 diabetes in Saudi Arabia during
2014–2022 ................................................................................................. 201
7.1.1. The overall and sex-specific prevalence of diabetes and numbers of
diabetic individuals in the Saudi population ............................................. 201
7.1.2. Age- and sex-specific prevalence of diabetes and numbers of
diabetic individuals ................................................................................. 211
7.1.3. Quantified effects of the assumed capping of obesity on the
modelling results for 2022 ....................................................................... 220
7.2. Overview of the main results for the whole modelling period
(1992-2022) ............................................................................................... 222
7.2.1. Comparison of the main results based on scenario 1 and
scenario 2 ............................................................................................... 222
7.2.2. Comparison of the main results based on scenario 3 and
scenario 4 ............................................................................................... 227
7.3. Impact of adjusting the modelling results of diabetes prevalence to the
more recent diagnostic criteria ................................................................... 231
7.3.1. Background .................................................................................. 231
7.3.2. Results of adjustment ................................................................... 233
Chapter 8. Using the Saudi IMPACT Diabetes Forecast Model for “What if”
analyses: quantifying the impact of the targeted reduction of obesity and
smoking prevalence in Saudi Arabia .......................................................... 236
8.1. Background ......................................................................................... 236
8.2. Local and international policy targets for adult obesity and smoking
prevalence ................................................................................................. 236
8.3. Impact of reducing the prevalence of obesity and smoking on the burden
of type 2 diabetes in Saudi Arabia .............................................................. 239
8.3.1. Methods ........................................................................................ 239
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