Received: 26 October 2017
Accepted: 4 January 2018
First Online: 12 February 2018
Ethics approval and consent to participate
: Before study entry, all participants signed an informed consent. The Lifelines Cohort Study is conducted according to the principles of the 1964 Declaration of Helsinki and its later amendments and in accordance with the research code of the University Medical Center Groningen (UMCG). The study has been approved by the medical ethics review committee of the UMCG.
: not applicable.
: The authors declare that they have no competing interests.
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