Article History
First Online: 30 June 2017
Compliance with Ethical Standards
:
: None of the authors have any conflicts of interest.
: All procedures performed in studies involving human participants were in accordance with the ethical standards of the University of Southampton and with the 1964 Helsinki Declaration and its later amendments or comparable ethical standards.
: The paper reports results of an analysis of anonymised secondary data accessed with permission from the UK Data Service. All authors have approved the manuscript for publication.