About the Authors
MRC/CSO Social and Public Health Service Unit, Glasgow, United Kingdom
Centre for Cognitive Ageing and Cognitive Epidemiology, Department of Psychology, University of Edinburgh, Edinburgh, United Kingdom
Department of Epidemiology and Public Health, University College London, London, United Kingdom
The authors have declared that no competing interests exist.
Analyzed the data: EW. Wrote the first draft: EW MB. Critically reviewed and contributed to the final version: EW IJD GD GDB MB.