title: Increased Cardiac Workload in the Upright Posture in Men: Noninvasive Hemodynamics in Men Versus Women.
abstract: Men and women differ in the risk of cardiovascular disease, but the underlying mechanisms are not completely understood. We examined possible sex-related differences in supine and upright cardiovascular regulation.
  
  
  
  Hemodynamics were recorded from 167 men and 167 women of matching age (≈45 years) and body mass index (≈26.5) during passive head-up tilt. None had diabetes mellitus or cardiovascular disease other than hypertension or used antihypertensive medication. Whole-body impedance cardiography, tonometric radial blood pressure, and heart rate variability were analyzed. Results were adjusted for height, smoking, alcohol intake, mean arterial pressure, plasma lipids, and glucose. Supine hemodynamic differences were minor: Men had lower heart rate (-4%) and higher stroke index (+7.5%) than women (P<0.05 for both). Upright systemic vascular resistance was lower (-10%), but stroke index (+15%), cardiac index (+16%), and left cardiac work were clearly higher (+20%) in men than in women (P<0.001 for all). Corresponding results were observed in a subgroup of men and postmenopausal women (n=76, aged >55 years). Heart rate variability analyses showed higher low:high frequency ratios in supine (P<0.001) and upright (P=0.003) positions in men.
  
  
  
  The foremost difference in cardiovascular regulation between sexes was higher upright hemodynamic workload for the heart in men, a finding not explained by known cardiovascular risk factors or hormonal differences before menopause. Heart rate variability analyses indicated higher sympathovagal balance in men regardless of body position. The deviations in upright hemodynamics could play a role in the differences in cardiovascular risk between men and women.
  
  
  
  URL: http://www.clinicaltrials.gov. Unique identifier: NCT01742702.
authors.affiliation: School of Medicine, University of Tampere, Finland pauliina.kangas@fimnet.fi.
authors.forename: Pauliina
authors.initials: P
authors.lastname: Kangas
authors.affiliation: School of Medicine, University of Tampere, Finland Department of Internal Medicine, Tampere University Hospital, Tampere, Finland.
authors.forename: Anna
authors.initials: A
authors.lastname: Tahvanainen
authors.affiliation: School of Medicine, University of Tampere, Finland Department of Clinical Physiology, Tampere University Hospital, Tampere, Finland.
authors.forename: Antti
authors.initials: A
authors.lastname: Tikkakoski
authors.affiliation: School of Medicine, University of Tampere, Finland Department of Internal Medicine, Tampere University Hospital, Tampere, Finland.
authors.forename: Jenni
authors.initials: J
authors.lastname: Koskela
authors.affiliation: Department of Electronics and Communication Engineering, Tampere University of Technology, Tampere, Finland.
authors.forename: Marko
authors.initials: M
authors.lastname: Uitto
authors.affiliation: Department of Electronics and Communication Engineering, Tampere University of Technology, Tampere, Finland.
authors.forename: Jari
authors.initials: J
authors.lastname: Viik
authors.affiliation: School of Medicine, University of Tampere, Finland Department of Clinical Physiology, Tampere University Hospital, Tampere, Finland.
authors.forename: Mika
authors.initials: M
authors.lastname: Kähönen
authors.affiliation: Department of Clinical Physiology, Tampere University Hospital, Tampere, Finland.
authors.forename: Tiit
authors.initials: T
authors.lastname: Kööbi
authors.affiliation: School of Medicine, University of Tampere, Finland Department of Internal Medicine, Tampere University Hospital, Tampere, Finland.
authors.forename: Jukka
authors.initials: J
authors.lastname: Mustonen
authors.affiliation: School of Medicine, University of Tampere, Finland Department of Internal Medicine, Tampere University Hospital, Tampere, Finland.
authors.forename: Ilkka
authors.initials: I
authors.lastname: Pörsti
mesh_terms: D015992:Body Mass Index; D002302:Cardiac Output / Q000502:physiology; D002318:Cardiovascular Diseases / Q000209:etiology / Q000503:physiopathology*; D004562:Electrocardiography; D005260:Female; D006339:Heart Rate / Q000502:physiology; D006439:Hemodynamics / Q000502:physiology*; D006801:Humans; D006973:Hypertension / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D011187:Posture / Q000502:physiology*; D012727:Sex Characteristics
keywords: cardiac output; hemodynamics; sex‐specific