We are grateful and indebted to Dr Mathew Zacharias (content editor) and Prof Nathan Pace (statistical editor) for their helpful comments that contributed to, and improved the quality of this review.

We would like to thank the following people.

Mrs Lynne Williams (peer reviewer) for commenting on the protocol. Dr Maureen O. Meade and Dr Malcolm G Booth (peer reviewers), Kathie Godfrey and Mark Edward (consumers) for commenting on the review.

Dr Phillipe Éckert, Mrs María Jesus García, Karin Kirchhoff, Dr Marin Kollef, Dr Leonardo Lorente, Mrs Donna Prentice, and Dr Arzu Topeli for their kind attention in providing additional information about their studies.

Mrs Marta Roqué for her statistical support with the first draft of this review.

Mrs Susanne Ebrahim (Cochrane Metabolic and Endocrine Disorders Review Group) for her help in translating German articles.

The authors would like to acknowledge the members of the Epidemiology Department who supported this study, particularly Dr. Xavier Bonfill, Ignasi Bolíbar, Ignasi Gich, Teresa Puig and Gerard Urrútia. We would also like to acknowledge the support provided by Carolyn Newey.

We would be grateful to any readers who provide further studies for assessment for future updates.