Data Sources
We evaluated patients with VVS who presented to the syncope
unit12, 13, 25 of Tehran Heart
Center,26 Tehran, Iran, for a head-up tilt table test
(HUTT) from February 2020 to February 2021 as the case group. The
control group was selected from the population-based Tehran Cohort Study
(TeCS) on adult inhabitants of Tehran.27 The
demographic and baseline data were retrieved from the syncope registry
of Tehran Heart Center25 for the case group and the
database of TeCS27 for the control group. The protocol
of this study was designed according to the Declarations of Helsinki
2013 and approved by the ethics committee of Tehran University of
Medical Sciences
(IR.TUMS.MEDICINE.REC.1397.856).
Informed consent was obtained from all participants after a detailed
discussion on the study protocol and before inclusion.