Aus dem Zentrum für Innere Medizin Bereich Endokrinologie & Diabetologie Leiter: Professor Dr. med. Dr. phil. Peter Herbert Kann des Fachbereichs Medizin der Philipps-Universität Marburg The change of lifestyle in an indigenous Namibian population group (Ovahimba) is associated with alterations of glucose metabolism, metabolic parameters, cortisol homeostasis and parameters of bone quality (quantitative ultrasound). Inaugural-Dissertation zur Erlangung des Doktorgrades der gesamten Humanmedizin dem Fachbereich Medizin der Philipps-Universität Marburg vorgelegt von Anneke M. Wilhelm geb. Voigts aus Windhoek/Namibia Marburg, 2014 II Angenommen vom Fachbereich der Medizin der Philipps-Universität Marburg am: 10. Juli 2014 Gedruckt mit Genehmigung des Fachbereichs. Dekan: Herr Prof. Dr. H. Schäfer Referent: Herr Prof. Dr. Dr. Peter Herbert Kann 1. Koreferent: Herr Prof. Dr. P. Hadji III IV to Martin and to my parents for their faith in me V VI Table of contents TABLE OF CONTENTS .............................................................................................. VII GENERAL INTRODUCTION ......................................................................................... 1 OBJECTIVES .............................................................................................................. 3 PART A THEORETICAL BACKGROUND .......................................................... 5 CHAPTER 1 DIABETES ......................................................................................... 6 1. Definition, Classification, Treatment ................................................... 6 1.1. Definition .............................................................................................. 6 1.2. Classification and treatment ................................................................. 7 1.1.1. Type 1 diabetes ................................................................................. 8 1.1.2. Type 2 diabetes ............................................................................... 11 1.1.3. Type 3 diabetes and other types ..................................................... 12 1.1.4. Types of diabetes in Africa ............................................................. 15 1.1.5. Gestational diabetes ........................................................................ 17 2. Epidemiology of diabetes ................................................................... 18 2.1. Prevalence of DM ............................................................................... 18 2.2. Prevalence of impaired glucose tolerance and impaired fasting glucose .................................................................................... 21 2.3. Prevalence of diabetes in Africa and Namibia specifically ................ 21 3. Causes of the diabetic epidemic ......................................................... 23 3.1. Demographical, epidemiological and socio-economic transitions ..... 23 3.2. Obesity ................................................................................................ 25 3.2.1. The pathophysiology of obesity and insulin resistance .................. 26 3.2.2. Prevalence of obesity ...................................................................... 27 3.2.3. The thrifty phenotype and thrifty genotype theory ......................... 29 3.3. The role of gestational diabetes .......................................................... 31 3.4. The role of cortisol ............................................................................. 31 3.4.1. Synthesis, function and metabolism of cortisol .............................. 31 3.4.2. Interaction of cortisol and diabetes ................................................. 33 3.5. The role of the metabolic syndrome ................................................... 35 3.5.1. Definition of the metabolic syndrome ............................................ 35 VII 3.5.2. Causes of the metabolic syndrome ................................................. 38 3.5.2.1. Obesity ................................................................................... 38 3.5.2.2. Insulin resistance .................................................................... 40 3.5.3. Prevalence of the metabolic syndrome ........................................... 40 3.5.4. Management of the metabolic syndrome........................................ 41 3.5.5. The metabolic syndrome in Africa ................................................. 42 4. Burden of the diabetes epidemic ........................................................ 44 4.1. The burden of mortality ...................................................................... 45 4.2. The burden of morbidity – DALY, YLL, YLD .................................. 47 4.3. The economic burden ......................................................................... 48 4.4. Predictions for future burden .............................................................. 51 4.5. The burden of indirect costs ............................................................... 52 5. Preventative strategies ....................................................................... 53 6. Diabetes type 2 – The African picture ................................................ 55 6.1. The challenge of communicable and non-communicable diseases .... 56 6.2. HIV/AIDS, tuberculosis and diabetes ................................................ 56 6.2.1. TB and diabetes .............................................................................. 57 6.2.2. HIV/AIDS and diabetes .................................................................. 58 6.3. Challenges faced by the epidemic ...................................................... 59 6.3.1. Diabetic complications in the African setting ................................ 60 6.3.2. Challenges in the treatment of diabetes in the African setting ....... 62 6.3.3. The role of traditional and faith healers.......................................... 62 7. The Framingham risk score (FRS) ..................................................... 65 CHAPTER 2 BONE ULTRASOUND AND OSTEOPOROSIS ....................................... 68 1. Definition ............................................................................................ 68 2. Clinical manifestation ........................................................................ 68 3. Epidemiology of osteoporosis ............................................................ 69 4. Burden of disease ............................................................................... 72 5. The physiology of bone ....................................................................... 75 6. Risk factors and prevention of osteoporosis ...................................... 76 7. Diagnosis of bone quality and osteoporosis ...................................... 77 8. Measurement of bone mass and acoustical properties of bone ......... 79 9. Ethnic differences in bone quality and osteoporosis .......................... 81 VIII CHAPTER 3 NAMIBIA ......................................................................................... 86 1. The Namibian profile ......................................................................... 86 1.1. The political structure ......................................................................... 87 1.2. The Namibian people.......................................................................... 89 1.2.1. Migration and urbanisation ............................................................. 91 1.3. The social context ............................................................................... 91 1.3.1. Education ........................................................................................ 92 1.3.2. Gender equality and social security ................................................ 94 1.3.3. The Human Development Index..................................................... 95 1.4. The economical context ...................................................................... 98 1.4.1. The mining sector ........................................................................... 99 1.4.2. The agricultural sector .................................................................. 100 1.4.3. The fishing sector ......................................................................... 100 1.4.4. The tourism sector ........................................................................ 100 1.4.5. Economic indicators ..................................................................... 101 1.4.6. Export, import and Namibia’s trading partners ............................ 103 1.4.7. Poverty and unemployment .......................................................... 104 1.4.8. The Affirmative Action Employment Act and Black Economic Empowerment.............................................................................. 106 1.5. Conclusion ........................................................................................ 107 2. The Namibian health system ............................................................ 108 2.1. The early days of the health system.................................................. 108 2.2. Set-up of the health system ............................................................... 109 2.3. Primary health-care approach ........................................................... 110 2.4. Different entities of the health-care system ...................................... 110 2.4.1. The public health-care sector .......................................................