3.3. Potential risk factors for the increased prevalence of diabetes in Saudi Arabia

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A Thesis Submitted for the Degree of PhD at the University of Warwick

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Dietary Factors and Type 2 Diabetes
Mellitus in Urban Saudi Adults

by

Lena Al Khudairy

A thesis submitted in partial fulfilment of the requirements for the degree
of Doctor of Philosophy in Health Sciences

University of Warwick, Warwick Medical School
May 2014
i
I dedicate this thesis to my beloved parents, Ghassan Al Khudairy and Rajaa Al Sayed
for their unconditional love and for their selfless and invaluable support throughout my
course of study

ii
Table of contents
List of tables viii
List of figures x
Acknowledgements xi
Declaration xiii
Abbreviations xiv
Abstract xvi
Introduction 1
1.1. Introduction 1
1.2. Overview of the thesis structure 2
Background 5
2.1. Country profile 5
2.2. The health care system in Saudi Arabia 7
Literature review 9
3.1. Overview on the prevalence of Type 2 diabetes in Saudi Arabia 9
3.2. Complications and co-morbidities 12
3.3. Potential risk factors for the increased prevalence of diabetes in Saudi
Arabia 14
Aims and objectives 33
4.1. Aims and objectives of this project 33
Dietary factors and T2DM in the Middle East: what is the evidence for an
association? – A systematic review 35
5.1. 35
Background
5.2. 37
Materials and Methods
5.3. 39
Results
5.4. 55
Methodological Quality of Included Studies
5.5. 62
Discussion
5.6. 67
Conclusion
The biomarkers screening in Riyadh (2009) survey methods 68
6.1. Biomarkers Research Program 68
6.2. 69
Collaboration
6.3. 70
The Biomarkers Screening in Riyadh Survey (2009) study design
6.4. 70
The Biomarkers Screening in Riyadh Survey (2009) study setting
6.5. 70
Ethical approval for the Biomarkers Screening in Riyadh Survey (2009)
6.6.
Participant selection of the Biomarkers Screening in Riyadh Survey
70
(2009)
6.7. 71
Data collection of the Biomarkers Screening in Riyadh Survey (2009)
6.8. Socio-demographic measurements and medical history 71
6.9. Anthropometric measurements 71
6.10. Dietary measurements 72
6.11. Biochemical and physiological measurements 73
6.12. Clinical diagnosis of chronic conditions 74
6.13. Variables included in the dataset provided by the Saudi collaborators 74
6.14. Data storage, preparation and cleaning 75
6.15. Dietary measurements preparation and cleaning 76
6.16. Dietary data entry 77
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6.17. Field work activities 77
Descriptive characteristics of the 2631 participants of this project 82
7.1. Materials and methods 82
7.2. Statistical analysis 83
7.3. Results 84
A) Socio-demographic characteristics 86
B) Anthropometric and lifestyle behaviour characteristics 88
C) Blood pressure and lipid parameters 91
D) Cardiovascular profile 91
E) Diabetes-related profile 92
F) Reproductive profile and the prevalence gestational diabetes history in
females 96
7.4. Discussion 97
Dietary factors and T2DM: the role of anthropometric measures 109
8.1. Methods 109
8.2. Statistical analysis 111
8.3. Results 112
A) Correlations between anthropometric measurements for the overall
sample 112
B) Odds ratio of T2DM prevalence by anthropometric measurements in the
overall sample 114
C) Odds ratio of T2DM prevalence by anthropometric measurements - sex-
stratified analyses 116
8.4. Discussion 120
Dietary factors and T2DM: calibration study and association of selected
food items with T2DM 126
Section 1 Calibration of the food frequency questionnaire against two
24-hour dietary recalls 127
9.1.1. 127
Methods
A) Study setting 127
B) Ethical approval 128
C) Dietary assessment methods 128
D) Rationale behind the choice of the reference tool (24-hour dietary
recall) 128
E) Food frequency questionnaire structure 130
F) 24-hour dietary recall structure 130
G) Number of recalls and which days 131
H) Sample size calculation 132
I) Selection of potential participants 133
J) Invitation of potential participants 134
K) Incentives 134
L) Mode of administration 136
M) Sequence of questionnaire administration 136
N) The FFQ interview 136
O) 24-hour dietary recall interview 137
9.1.2. Analysis 139
A) Nutritional analysis 139
B) Statistical analysis 141
9.1.3. Results 143
A) Response rate 143
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B) Comparison of the FFQ with 24 hour recalls 145
9.1.4. 9.1.4. Discussion 148
Section 2 Dietary factors and T2DM, the role of selected food and
beverages and T2DM 152
9.2.1. Methods 152
A) Nutritional tool – the FFQ 152
B) Food items selection 152
C) Sample selection 153
9.2.2. Analysis 154
A) Nutritional analysis 154
B) Statistical analysis 155
9.2.3. Results 157
A) Descriptive characteristics 157
B) Associations between selected food items and T2DM in the overall
sample 163
C) Associations between beverage intake and T2DM in the overall sample 165
D) Sex stratified associations between selected food items and T2DM 166
E) Sex stratified associations between beverage intake and T2DM 166
9.2.4. Discussion 172
Dietary factors and T2DM: the role of dietary biomarkers 177
10.1. Methods 177
A) Biomarkers selection 177
B) Sample size calculation 178
C) Sample selection 178
D) Biochemical analysis 179
10.2. Statistical analysis 181
10.3. Results 182
A) Comparison between the sub-sample and the original cohort 182
B) Descriptive characteristics of the sub-sample 184
Section 1 Vitamin D and T2DM 187
10.1.1. Results 187
A) Sex stratified characteristics across tertiles of 25 (OH) D 187

B) Correlates of 25 (OH) Dlevels 191

C) Interaction between 25(OH) D and covariates (age and BMI) 193
D) Mean levels of 25(OH)Dand diabetes 194

10.1.2. Discussion 195
Section 2 Selenium and T2DM 203
10.2.1. Results 203
A) Sex-specific characteristics across tertiles of selenium 203
B) Correlates of serum Se 204
C) Interaction between serum Se levels and covariates (age and BMI) 208
D) Mean levels of serum Se across diabetes groups 208
10.2.2. Discussion 209
Cultural barriers to healthy eating in Saudi adults with and without T2DM 214
11.1. Rational 214
Section 1 The pilot study of the cultural barriers to healthy eating
questionnaire 216
11.1.1. Methods 216
A) Rational for the pilot study and questionnaire development 216
B) Questionnaire structure 217
C) Study setting 218
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D) Selection of participants 218
E) Interview structure 218
F) Analysis plan 219
11.1.2. Lessons learnt from the pilot study 221
A) Study setting 221
B) Sample selection 221
C) Interview structure 221
D) Questionnaire format 222
E) Questions content and format 222
F) Incentives 223
G) Analysis 223
H) Back translation 224
Section 2 Cultural barriers to healthy eating and T2DM 225
11.2.1. Methods 225
A) Study setting 225
B) Sampling plan 226
C) Selection of potential participants 227
D) Invitation of potential participants 228
E) Incentives 228
F) Mode of administration 228
G) Questionnaire structure 229
H) Interview structure 229
11.2.2. Data analysis 230
A) Data preparation and data entry 230
B) Qualitative data (the first section of the questionnaire – free text data) 231
C) Quantitative data analysis 238
11.2.3. Results 240
A) Response rate 240
B) Section one: Qualitative findings (free text data) 241
C) Section two. Quantitative findings: barriers to healthy eating
questionnaire (closed-ended questions) 259
D) Section three. Dietary misconceptions in T2DM questionnaire (closed-
ended questions) 262
11.2.4. Discussion 270
Discussion 276
12.1. Principal findings of this project 276
12.2. Strengths and limitations of this project 283
12.3. Comparison with previous studies 287
12.4. Implications for policy 302
12.5. Implications for practice 304
12.6. Implications for research 305
12.7. Conclusion 306
12.8. Scientific outputs 308
References 310
Appendix 1: The Biomarkers Screening Survey (2009) questionnaire 467
Appendix 2: The Biomarkers Screening Survey (2009) food frequency
questionnaire 471
Appendix 3: Agreement between the Saudi collaborators and Warwick Medical
School for the purpose of this project 483
Appendix 4: Ethical approval for the Biomarkers Screening Survey (2009) in
English and Arabic copy 485
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Appendix 5: Comparison* between participants with (n = 2631) and without
dietary data (n = 529) 487
Appendix 6: Comparison* between participants that were aware of their
diabetes and unaware of their diabetes at the time of the 2009 survey for
anthropometric measures 488
Appendix 7: Odds ratio for T2DM prevalence: NDM vs. Unaware of T2DM (at
the time of the 2009 survey) in comparison to NDM vs. T2DM (both aware and
unaware of T2DM) 489
Appendix 8: Ethical approval from the Ethics Committee of the College of
Medicine Research Centre, King Saud University, Riyadh, KSA 490
Appendix 9: Ethical approval from the Biomedical Research Ethics Committee
of the University of Warwick 492
Appendix 10: The food frequency questionnaire administered in the calibration
study 493
Appendix 11: The 24 hour questionnaire used in the calibration study 497
Appendix 12: Comparison* between participants that were unaware of T2DM
and aware of T2DM 498
Appendix 13: The pilot study questionnaire 499
Appendix 14: The modified questionnaire used in this project 503
Appendix 15: Visual examples on the process of qualitative analysis 507

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List of tables
Table 3.1. Epidemiological studies on the prevalence of T2DM in Saudi Arabia 11
Table 3.2. The prevalence of T2DM in Gulf countries 11
Table 3.3. Diabetes profile in Saudi Arabia 12
Table 3.4. Common complications of T2DM in Saudi Arabia 13
Table 5.1. Association of energy, nutrients, foods, and beverages with T2DM 41
Table 5.2. Association between dietary patterns and T2DM 44
Tables 5.3. Association between lifestyle factors and T2DM in intervention
studies 47
Table 5.4. Methodological quality of the cohort study and case-control studies 55
Table 6.1. Field work activities 78
Table 7.1. Baseline characteristics of the overall sample 85
Table 7.2. Socio-demographic characteristics 87
Table 7.3. Anthropometric characteristics and lifestyle behaviours 89
Table 7.4. Blood pressure and lipid parameters 93
Table 7.5. Cardiovascular profile 94
Table 7.6. Diabetes profile 95
Table 7.7. Reproductive profile 96
Table 8.1. Pearson correlation coefficients between anthropometric
measurements of the baseline sample 113
Table 8.2. Sex stratified correlations between anthropometric measurements 113
Table 8.3. Odds ratio (95% CI) of T2DM prevalence by anthropometric
measures of the overall sample 115
Table 8.4. Odds ratio (95% CI) of T2DM prevalence by anthropometric 117
measures stratified by sex
Table 9.1. Participating PHCCs in the current study 127
Table 9.2. Descriptive characteristics of respondents, and non-respondents, and
original cohort 144
Table 9.3. Correlations between the FFQ and the two 24-hour dietary recalls 147
Table 9.4. Variance components of the food intakes estimated by two 24 hour
recalls 148
Table 9.5. Descriptive characteristics of the sample 158
Table 9.6. Descriptive characteristics stratified by sex and diabetes status 161
Table 9.7. Association between food variables and T2DM in the overall sample 163
Table 9.8. Association between beverages variables and T2DM in the overall
sample 165
Table 9.9. Sex stratified associations between food intake and T2DM 167
Table 9.10. Sex stratified associations between beverage intake and T2DM 170
Table 10.1. Comparison of characteristics between the sub-sample and the
original cohort 183
Table 10.2. Descriptive characteristics of the sub-sample 185
Table 10.3. Characteristics stratified by sex across tertiles of 25 (OH) D 189
Table 10.4. Pearson correlation coefficients between 25 (OH) D and covariates
for the overall sub-sample 191
Table 10.5. Sex stratified correlations between 25 (OH) D and covariates 192
Table 10.6. Testing for interaction between 25 (OH) Dand age 193

Table 10.7. Testing for interaction between 25(OH) Dand BMI 193

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Table 10.8. Prevalence of diabetes across 25(OH) D in males (by the median of 194
age)
Table 10.9. Analysis of mean levels of 25(OH)D across diabetes groups (95%
CI) 194
Table 10.10. Sex-specific characteristics across tertiles of serum Se 205
Table 10.11. Pearson correlation coefficients between Se and covariates for the
overall sub-sample 207
Table 10.12. Sex stratified correlations between Se and covariates 207
Table 10.13. Testing for interaction between serum selenium and age 208
Table 10.14. Testing for interaction between serum selenium and BMI 208
Table 10.15. Analysis of mean levels of serum Se across diabetes groups (95%
CI) 209
Table 11.1. Participating PHCC’s in the pilot study 218
Table 11.2. Participating PHCC’s in the current study 225
Table 11.3. Coding frame for question 1: How would you describe a healthy
diet? 233
Table 11.4. Coding frame for question 4: Do you which know the foods that
people eat less to prevent diabetes? 235
Table 11.5. Descriptive characteristics of the respondents and non respondents 240
Table 11.6. Summary of themes and definitions for the overall data 243
Table 11.7. Barriers to healthy eating for the overall sample 259
Table 11.8. Barriers to healthy eating stratified by sex and diabetes 261
Table 11.9. Dietary misconceptions for the overall sample 262
Table 11.10. Dietary misconceptions stratified by sex and diabetes 267

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