CONTENTS
List of abbreviations ii
Abstract 1
1. Background 3
1.1 Background and aim of the review 3
1.2 Definitional and conceptual issues 4
1.3 Policy and practice background 9
1.4 Research background 10
1.5 Authors, funders and other users of the review 15
1.6 Review questions 16
1.7 Outline of the report 16
2. Methods used in the review 17
2.1 User involvement 17
2.2 Identifying studies 18
2.3 In-depth review: synthesis process 22
2.4 Summary 30
3. Identifying and describing studies: Results 31
3.1 Overview 31
3.2 Results from searching and screening electronic databases 31
3.3 Description of the included studies 32
3.4 Summary 35
4. In-depth review: Results 36
4.1. Overview 36
4.2 Meta-regression analysis 36
4.3 Results from' count of evidence 44
4.4 Textual narration 66
5.mplications 94
5.1 Main findings 94
5.2 Strengths and limitations of this systematic review 95
5.3 mplications 96
6. references 100
6.1 Studies included in the synthesis 100
6.2 Studies included in the text of the report 104
Appendices 108
Appendix 1.1: Authorship and acknowledgements 108
Appendix 2.1: Search strategy for electronic databases 109
Appendix 2.2: Critical appraisal tool 114
Appendix 2.3: Characterisation of included studies 123
Appendix 3.1: List of outcome indicators 204