title: Gender differences in orthostatic tolerance in the elderly.
abstract: BACKGROUND
  Gender differences in orthostatic tolerance in the elderly are poorly studied and understood.
  
  
  METHODS
  48 healthy elderly over 65 years (24 women), free from medication and without chronic diseases, were subjected to head-up tilt (HUT) tests: 30° for 10 min and 70° for 40 min. Blood pressures, stroke volume, total peripheral resistance, blood pressure variability, heart rate variability and baroreceptor sensitivity were measured and test terminations due to vasovagal syncope or unbearable presyncopal symptoms were registered.
  
  
  RESULTS
  Mean age was 72; women and men differed in body mass index; 22.2 versus 24.8, respectively (p < 0.01). Mean blood pressures were lower among women, with 88 and 98 mmHg, respectively (p < 0.01) (rest) and 86 and 96 mmHg (p < 0.01) (tilt 30°). Mean total peripheral resistance index was significantly higher among women during 70° tilt, 13.5 versus 10.8 (p < 0.01); no gender differences in heart rate were seen. Women had lower LF/HF ratio (an index of sympathovagal balance) at rest and during 30° tilt (both p < 0.05); other heart rate variability measures and baroreceptor sensitivity did not differ. Two women, 9 %, and 8 men, 33 %, terminated head-up tilt test due to vasovagal syncope or presyncopal symptoms. Gender difference was marginally significant (p = 0.05, log-rank test). Higher heart rate at rest (p < 0.01) was the only variable significantly associated with the risk of syncope.
  
  
  CONCLUSIONS
  Our results indicate that elderly men have poorer orthostatic tolerance during protracted postural stress than women of the same age. The underlying reason might be differences in vascular rather than cardiac autonomic control.
authors.affiliation: Department of Geriatric Medicine, Oslo University Hospital, Oslo, Norway, cmelling@online.no.
authors.forename: Marte Rognstad
authors.initials: MR
authors.lastname: Mellingsæter
authors.forename: Vegard Bruun
authors.initials: VB
authors.lastname: Wyller
authors.forename: Torgeir Bruun
authors.initials: TB
authors.lastname: Wyller
authors.forename: Anette Hylen
authors.initials: AH
authors.lastname: Ranhoff
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001794:Blood Pressure / Q000502:physiology; D004244:Dizziness / Q000503:physiopathology*; D005260:Female; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D008297:Male; D011187:Posture / Q000502:physiology*; D011311:Pressoreceptors / Q000502:physiology / Q000503:physiopathology; D012737:Sex Factors; D013318:Stroke Volume / Q000502:physiology; D013575:Syncope / Q000503:physiopathology; D018667:Tilt-Table Test / Q000379:methods; D014655:Vascular Resistance / Q000502:physiology