1 Swansea University, Swansea, UK
4 Department of Statistics, Swansea University, Swansea, UK
5 Public Health Wales, Swansea, UK
7 Cardiff University, Wales, UK
8 Department of Public Health Medicine, Swansea University, Swansea, UK
9 Department of Medical Statistics, Cardiff University, Wales, UK
Correspondence: Sinead Brophy, PhD, College of Medicine, Swansea University, Grove Building Singleton Park, Swansea SA2 8PP, UK. E-mail: s.brophy@swansea.ac.uk
