Funding for this research was provided by:
MRC University of Bristol Integrative Epidemiology Unit (MC_UU_12013/9)
Sigmund Gestetner Foundation
Received: 7 September 2017
Accepted: 1 May 2018
First Online: 29 May 2018
Ethics approval and consent to participate
: The protocol for this study was approved by the CPRD’s Independent Scientific Advisory Committee (ISAC protocol 15_246R). This study did not directly involve patients, so further ethical approval was not required.
: The authors declare that they have no competing interests.
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