Received: 25 May 2019
Accepted: 26 June 2019
First Online: 1 July 2019
Ethics approval and consent to participate
: The National Health Research Ethic Committee approved the NDHS in Nigeria (NHREC/01/2007). MEASURE DHS, the custodian of the NDHS datasets authorised access to the data analysed in the study. The analyses are in anonymised form, and thus not offensive to any individual or community. The datasets are available for use by the general public.
: Not applicable.
: The authors declare that they have no competing interests.