About the Authors
Department of Social Medicine, University of Bristol, Bristol, United Kingdom
Medical Research Council Centre for Causal Analyses in Translational Epidemiology, University of Bristol, Bristol, United Kingdom
The authors have declared that no competing interests exist.
LC and SJL designed the study, analyzed the data, and contributed to writing the paper. GDS designed the experiments and contributed to writing the paper. RMH analyzed the data and contributed to writing the paper. Both LC and SJL had full access to all of the data in the study and take responsibility for the integrity of the data and the accuracy of the data analysis.