Adiposity and cvd risk factors: a comparison between ethnicities



Download 4.55 Mb.
Page1/24
Date18.05.2018
Size4.55 Mb.
  1   2   3   4   5   6   7   8   9   ...   24

ADIPOSITY AND CVD RISK FACTORS:

A COMPARISON BETWEEN ETHNICITIES

A thesis submitted for the degree of Doctor of Philosophy

By

NONSIKELELO MATHE

Research Centre for Society and Health

Buckinghamshire New University

Brunel University

October 2010


ABSTRACT

Background: The prevalence of overweight, obesity and obesity-related disease, mainly cardiovascular disease (CVD), is increasing in both developed and developing countries. Ethnic differences have been reported in the prevalence of overweight, obesity and CVD. However, measures used to define overweight and obesity, and identify increased risk of CVD were developed and validated in predominately Caucasian populations in developed countries. Consequently, these measures may not accurately define disease risk in all population groups. Therefore the specific aims of this programme of study were:

  1. To establish the relationship between adiposity and cardiovascular risk factors in different ethnic groups.

  2. To identify field measures of adiposity, relating to cardiovascular risk in different ethnic groups.

  3. To compare the relationship of adiposity and cardiovascular risk factors in a single ethnic group, that of a rural and an urban population in Zimbabwe.

  4. To identify risk factors for CVD related to adiposity in a population of African origin.

Study design:

Three empirical studies were undertaken. In study one, 312 adult subjects from three ethnic groups (Afro-Caribbean (n=106), Caucasian (n=165) and South Asian (n=41)) were recruited from a University. Twenty-six (26) of each group were individually matched for age (±3 years) gender and BMI (±2 kg/m2) to allow for comparability. Measures of body composition included height, weight, waist and hip circumferences, skinfold thickness measures, body density and percentagebody fat.

In study two, 81 subjects from two ethnic groups (Afro-Caribbean (n=39) and Caucasian (n=42)) were recruited and tested. They were matched for age, gender and BMI using the same criteria as study one. In addition to the body composition measures taken in study one, random non-fasting blood glucose, total cholesterol, triglycerides and blood pressure were taken.

In study three, 55 men and 108 women from rural Zimbabwe, 8 men and 17 women from an urban low-density suburb in Harare Zimbabwe, and 28 male and 16 female students from the University of Zimbabwe were recruited and tested. In addition to all measures of body composition in studies one and metabolic analysis in study two, participants’ dietary intake was assessed by food frequency questionnaire and 24hour recall and physical activity was assessed by a physical activity questionnaire.



Main findings:

  • The relationship between BMI and %BF was not the same in all ethnic groups. (aim 1)

  • There were ethnic differences in the cardiovascular risk predictors between Afro-Caribbean and Caucasian men and women. (aim 1)

  • It is not recommended that BIA is used as a substitute for TBW estimation in multi-compartment models. (aim 2)

  • In three groups of Zimbabweans from urban, rural and university locations, a pattern emerged. Amongst women, urban women were at greatest risk, reporting highest values for all variables, followed by rural then university women. Amongst men, urban men were at highest risk, however there were few differences between rural and university men. (aim 3).

  • Finally, increased WC and dyslipidemia are associated with increasing BMI in populations of African origin. (aim 4)

Conclusions:

The relationships between overweight, obesity and risk of obesity-related disease differ between different ethnic groups. Moreover, in the groups from Zimbabwe, differences in obesity-related risk were associated with being female and living in urban areas. Therefore, application of universal measures for defining obesity and related diseases may not be applicable to all ethnic groups.

TABLE OF CONTENTS


ABSTRACT ii

TABLE OF CONTENTS iv

LIST OF FIGURES xiv

LIST OF TABLES xv

ABBREVIATIONS xviii

ACKNOWLEDGEMENTS xx

AUTHORS DECLARATION xxi

chapter 1: INTRODUCTION 1

1.1 Context 1

1.2 Aims 3

a. Study objectives: 3

i. Study one: Measurement of adiposity in three ethnic groups 4

ii. Study two: Adiposity and cardiovascular risk factors in Afro-Caribbean and Caucasian men and women 4

iii. Study three: Adiposity and cardiovascular risk factors in rural and urban Zimbabweans 4



1.3 Thesis narrative 5

1.4 Thesis outline 7

1.5 References 8

chapter 2: ETHNIC DIFFERENCES IN OVERWEIGHT AND OBESITY 11

2.1 Introduction 11

2.2 Classification of obesity 12

2.3 Global prevalence of overweight and obesity 13

2.3.1 Ethnic differences in overweight and obesity prevalence 15

2.4 Overweight and obesity-related disease 18

2.4.1 Global prevalence of obesity-related disease 20

2.4.1.1 Cardiovascular Disease 21

2.4.1.2 Type II diabetes mellitus 21

2.4.1.3 Hypertension 22



2.4.2 Ethnic differences in obesity-related disease 22

2.5 Central obesity 26

2.5.1 Classification of central obesity 26

2.5.2 Ethnic differences in central obesity 28

2.5.3.1 Ethnic differences in visceral adiposity 29



2.6 Ethnic differences in obesity measurement 32

2.6.1 Body mass index 32

2.6.2 Waist Circumference 35

2.7 Conclusion 37

2.8 References 38

chapter 3: AN HISTORICAL REVIEW OF BODY COMPOSITION ASSUMPTIONS AND METHODS 43

3.1 Introduction 43

3.2 Cadaver studies 44

3.3 Characteristics of body components 45

3.3.1 Fat mass 46

3.3.2 Fat free mass 47

3.3.2.1 Hydration of fat free mass 48

3.3.2.2 Protein content of fat free mass 48

3.3.2.3 Mineralisation of fat free mass 49



3.4 Body composition models 50

3.4.1 The two-compartment model of body composition 50

3.4.1.1 Assumptions 50

3.4.1.2 Limitations and sources of error in the two-compartment model 51

3.4.1.3 Ethnic considerations 51



3.4.2 Three-compartment models 52

3.4.3 The four-compartment model 53

3.4.4 Multi- compartmental models 53

3.6 In vivo body composition methods 55

3.6.1 Air displacement plethysmography 57

3.6.1.1 Validity of air displacement plethysmography for estimating percentagebody fat 60

3.6.1.2 Air displacement plethysmography in different ethnic groups 65

3.6.2 Bioelectric Impedance Analysis 68

3.6.2.1 Validity of BIA of estimation of body fat in different ethnic groups 69



3.6.3 Anthropometry 70

3.6.4.1 Skinfold thickness measurement 71



3.7 Conclusion 74

3.8 References 75

chapter 4: BODY MASS INDEX AND ADIPOSITY IN THREE ETHNIC GROUPS 87

4.1 Introduction 87

4.2 Methods 89

4.2.1 Subjects 89

4.2.1.1 Ethical Approval 90

4.2.1.2 Selection Criteria 90

4.2.1.3 Ethnic Origin 90



4.2.2 Outcome Measures 90

4.2.2.1 Anthropometry 91

4.2.2.3 Air displacement plethysmography 91

4.2.3 Statistical Analysis 92

4.3 Results 93

4.3.1 Unmatched group comparisons 94

4.3.2 Matched group comparisons 95

4.3.2.1 Relationship between body mass index and % body fat 96

4.3.2.2 Age, gender, body mass index and ethnicity as predictors of percentagebody fat 96

4.4 Discussion 98

4.4.1 Effect of individual matching for age, gender and body mass index 99

4.4.2 Use of different methods for estimating % body fat in different ethnic groups 100

4.4.3 Implications for the use of BMI as a proxy for adiposity 101

4.4.4 Study limitations 101

4.5 Conclusion 102

4.6 References 102

chapter 5: A COMPARISON OF TWO COMPARTMENT DENSITOMETRY EQUATIONS FOR THE ESTIMATION OF percentageBODY FAT IN AFRO-CARIBBEANS 107

5.1 Introduction 107

5.2 Methods 112

5.2.1 Subjects 112

5.2.2 Outcome Measures 112

5.2.2.1 Anthropometry 112

5.2.2.2 Body density 113

5.2.2.3 Bioelectric Impedance Analysis 113

5.2.2.4 Two–compartmental densitometry equations 114

5.2.2.5 The reference model 115



5.2.3 Statistical analysis 115

5.3 Results 116

5.3.1 Comparison of two-compartment equations with reference in Afro-Caribbean men and women 116

5.3.2 Comparison of density of FFM in Afro-Caribbean and Caucasian group 120

5.4 Discussion 121

5.4.1 Ethnic specific versus generalised equations in Afro-Caribbean men and women 121

5.4.2 Modified three compartment reference model 122

5.4.5 Study limitations 123

5.5 Conclusion 124

5.6 References 124

chapter 6: A STUDY OF CVD RISK FACTORS IN AFRO-CARIBBEANS AND CAUCASIANS 127

6.1 Introduction 127

6.2 Methods 129

6.2.1 Subjects 129

6.2.1.1 Ethical approval and selection criteria 129

6.2.1.2 Ethnicity 130

6.2.2 Outcome measures 130

6.2.2.1. The Framingham risk score 130



6.2.3 Statistical analysis 131

6.3 Results 131

6.3.1 Ten-year cardiovascular risk 133

6.3.2 Predictors of CVD risk in Afro-Caribbeans compared with Caucasians 133

6.4 Discussion 134

6.4.1 Study limitations 135

6.5 Conclusion 136

6.6 References 137

chapter 7: THE NUTRITION TRANSITION: A CASE STUDY OF ZIMBABWE 141

7.1 Introduction 141

7.2 Description of the nutrition transition 143

7.3 Drivers of the nutrition transition in developing countries 145

7.3.1 Urbanisation and diet 146

7.3.2 Urbanisation and physical activity 147

7.4 Consequences of nutrition transition 148

7.4.1 Double burden of malnutrition and disease 149

7.5 Zimbabwe 151

7.5.1 The population 152

7.5.2 The economy 154

7.5.3 Urbanisation 156

7.5.4 Evidence of dietary transition in Zimbabwe 156

7.5.5 Evidence of changes in physical activity 160

7.5.6 Double burden of disease in Zimbabwe 163

7.5.6.1 Selected risk factors for CVD in Zimbabwe 165



7.6 Conclusion 169

7.7 References 170

chapter 8: COMPARISON OF ANTHROPOMETRIC AND DEMOGRAPHIC PROFILES OF A GROUP OF URBAN AND RURAL ZIMBABWEANS 175

8.1 Introduction 175

8.2 Methods 177

8.2.1 Subjects 177

8.2.2 Ethical approval 177

8.2.3 Study sites 177

8.2.4 Recruitment strategy 178

8.2.5 Outcome measures 178

8.2.5.1 Demographics and socio-economic variables 178

8.2.5.2 Anthropometry 179

8.2.6 Statistical analysis 180

8.3 Results 181

8.3.1 Demographics and socio-economic variables 181

8.3.1.1 Mean age 182

8.3.1.2 Marital status 183

8.3.1.3 Education 183

8.3.1.4 Employment status 183

8.3.1.5 Number of dependents 184



8.3.2 Anthropometric measures of adiposity 184

8.4 Discussion 186

8.4.1 Demographic and socio-economic differences 186

8.4.2 Anthropometric differences 187

8.4.3 Study limitations 188

8.5 Conclusion 189

8.6 References 190

chapter 9: ENERGY BALANCE IN A SAMPLE OF RURAL AND URBAN ZIMBABWEANS 192

9.1 Introduction 192

9.2 Methods 195

9.2.1 Outcome measures 195

9.2.1.1 Energy intake 195

9.2.1.2 Total energy expenditure (TEE) 196

9.2.2 Statistical analysis 196

9.3 Results 197

9.3.1 Comparison of daily energy intake and dietary patterns in urban and rural Zimbabweans. 197

9.3.2 Comparison of energy expenditure and physical activity patterns in rural and urban Zimbabweans 199

9.3.3 Comparison of energy balance in rural and urban Zimbabweans 200

9.4 Discussion 200

9.5 Conclusion 203

9.6 References 204

chapter 10: BLOOD PRESSURE, BLOOD GLUCOSE AND LIPID PROFILES IN RURAL AND URBAN ZIMBABWEANS 207

10.1 Introduction 207

10.2 Methods 209

10.2.1 Outcome measures 210

10.2.1.1 Health history and Smoking status 210

10.2.1.2 Blood pressure 210

10.2.1.4 Blood lipids and glucose 211



10.2.2 Statistical analysis 211

10.3 Results 212

10.3.1 Previous health history and history of health checks 213

10.3.1.1 Last blood pressure check 214

10.3.1.2 Last blood cholesterol check 214

10.3.1.3 Last blood glucose check 214

10.3.1.4 Smoking status 215

10.3.1.5 Previous diagnosis of disease 215



10.3.2 Blood pressure, lipids and glucose 216

10.3.2.1 Blood pressure 217

10.3.2.2 Non-fasting blood glucose 217

10.3.2.3 Non-fasting total cholesterol 217



10.4 Discussion 218

10.4.1 Risk factor screening 219

10.4.2 Differences in blood pressure, lipids and glucose 219

10.4.3 Study limitations 222

10.5 Conclusion 222

10.6 References 223

chapter 11: ADIPOSITY AND CARDIOVASCULAR RISK FACTORS IN ADULTS OF AFRICAN ORIGIN 227

11.1 Introduction 227

11.2 Methods 229

11.2.1 Subjects 229

11.2.2 Outcome measures 229

11.2.1.1 Anthropometric measures 229

11.2.1.2. CVD risk factors 229

11.2.2 Statistical analysis 230

11.3 Results 231

11.4 Discussion 233

11.4.1 Study limitations 235

11.5 Conclusion 236

11.6 References 236

chapter 12: THESIS SUMMARY, LIMITATIONS AND RECOMMENDATIONS 238

12.1 Summary 238

12.1.1 Summary of chapter two 239

12.1.2 Summary of chapter three 239

12.1.3 Summary of chapter four 239

12.1.4 Summary of chapter five 240

12.1.5 Summary of chapter six 241

12.1.6 Summary of chapter seven 241

12.1.7 Summary of chapter eight 242

12.1.8 Summary of chapter nine 243

12.1.9 Summary of chapter ten 244

12.1.10 Summary of chapter eleven 245

12.2 Limitations 246

12.3 Recommendations for future work 247

12.4 Conclusion 248

12.4.1 Public health implications 249

APPENDICES 251

APPENDIX 2.1 :Ethnicity 251

APPENDIX 3.1: THE BRUSSELS CADAVER ANALYSIS SERIES 255

APPENDIX 4.1: UK ETHNIC CATEGORIES, CENSUS (2001) 258

APPENDIX 8.1 FIELDWORK BOOK 259

LIST OF FIGURES



LIST OF TABLES

ABBREVIATIONS

AA- African American

ADP- Air Displacement Plethysmography

ATP III- Adult Treatment Panel Three

BIA- Bioelectric Impedence Analysis

BMI- Body Mass Index

CA- Caucasian American

CHD- Coronary Heart Disease

CVD- Cardiovascular Disease

CT- Computed Tomography

DFFM – Density of Fat Free Mass

DFM –Density of Fat Mass

ESRF- End-Stage Renal Failure

FAO- Food and Agriculture Organization

FFA- Free Fatty Acids

FFM- Fat Free Mass

FM- Fat Mass

HD-Hydrodensitometry

HDL-C-High Density Lipoprotein Cholesterol

HFFM- Hydration of Fat Free Mass

HSE- Health Survey for England

IDF- International Diabetes Federation

IHD- Ischemic Heart Disease

LDL-C – Low density Lipoprotein Cholesterol

LPL- Lipoprotein Lipase

METS- Metabolic Equivalents

MetS- Metabolic Syndrome

MFFM –Mineralisation of Fat Free Mass

MI- Myocardial Infarction

NCEP- National Cholesterol Education Programme

NHLBI- National Heart Lung and Blood Institute

NIH- National Institute of Health

PALS-Physical Activity Levels

SAA- Surface Area Artifact

SAT- Subcutaneous Adipose Tissue

SD- Sagittal Diameter

TBW- Total Body Water

TEE- Total Energy Expenditure

T2DM- Type 2 Diabetes Mellitus

TGV- Thoracic Gas Volume

VAT- Visceral Adipose Tissue

WHO- World Health Organization

WC- Waist Circumference

WHR- Waist-to-Hip Ratio

%BF- Percentage body fat

ACKNOWLEDGEMENTS

I am eternally indebted to my supervisors Professor David Brodie and Dr Joan Gandy for their tireless efforts, patience, knowledge and guidance throughout these years.

I am grateful for the advice and guidance I received from the late Professor Lucie Malaba and colleagues at the University of Zimbabwe.

To Dr Paul Amuna and Dr Francis Zotor at the University of Greenwich who assisted with software for dietary analysis.

Many thanks to Fortune Maduma, Lydia Muzangwa, Mthulisi Dube, and Cynthia Matare who assisted me with data collection in Zimbabwe.

I am grateful to Paul Sharp from Point of Care Services for his ingenious idea for a battery charger which was invaluable in my fieldwork in rural Zimbabwe.

To Dumisani Nyoni, Mrs Sithembiso Nyoni and staff members of ORAP Zimbabwe who assisted with accommodation and transportation during the fieldwork in rural Nkayi, Zimbabwe.

To all those who participated in the studies in the UK and Zimbabwe.

To my friends who’ve provided useful diversion at times of high stress

To Dr David Shaw for his moral support throughout the years

To my family, especially my uncle Kidwell and Aunt Ann and my cousins who have been very supportive.

To my sister, Sibonile for her support

Finally and most importantly, I am especially grateful to my mother, Reginah Mathe, for her unconditional support, encouragement and love, without which none of this would have been possible.



I dedicate this thesis to my father Fortune Mathe, who is missed dearly.

AUTHORS DECLARATION

I take responsibility for all the material contained within this thesis and confirm this is my own work.

Nonsikelelo Mathe

This thesis has been supplied on condition that anyone who consults it is understood to recognise that its copyright rests with the author under terms of the United Kingdom Copyright Acts. No quotation from this thesis and no information from it may be published without proper acknowledgement.


  1. INTRODUCTION





Share with your friends:
  1   2   3   4   5   6   7   8   9   ...   24


The database is protected by copyright ©dentisty.org 2019
send message

    Main page