title: Aging and arterial blood pressure variability during orthostatic challenge.
abstract: BACKGROUND
  It has been demonstrated that a decrease in vagal cardiac function compromises arterial blood pressure (ABP) stability during orthostatic challenge. Augmentations in low-frequency (LF) ABP oscillations are indicative of this change in autonomic hemodynamic control. Aging is associated with diminished arterial baroreflex sensitivity and vagal cardiac dysfunction. However, the effect of aging on the stability of ABP during an orthostatic challenge remains to be elucidated.
  
  
  OBJECTIVE
  The purpose of this study was to investigate ABP stability with aging during central hypovolemia induced by lower-body negative pressure (LBNP).
  
  
  METHODS
  Graded LBNP up to -40 mm Hg was applied in 16 older (65 +/- 3 years of age) and 16 younger (25 +/- 3 years of age) healthy adults. ABP variability was analyzed by fast Fourier transform. LF spectral density (0.04-0.15 Hz) was extracted to provide an index of vasomotor responsiveness.
  
  
  RESULTS
  Both LF systolic blood pressure (SBP) variability and diastolic blood pressure variability were augmented with LBNP. The rate of increase in LF SBP variability was augmented significantly greater in older as compared with younger subjects (p = 0.049). In addition, LF SBP variability was inversely correlated with decreases in pulse pressure in both age groups (r = -0.84, p = 0.01). The magnitude of the decreases in SBP and pulse pressure during LBNP was significantly affected by age, with the largest changes occurring in older subjects. The altered ABP response that manifested in older individuals was associated with a significant diminution in the reflex tachycardiac response elicited by LBNP.
  
  
  CONCLUSIONS
  Induction of central hypovolemia via graded LBNP augments LF ABP variability. This increased ABP variability is significantly greater in older individuals. Our data suggest that aging is associated with ABP instability during orthostatic challenge.
authors.affiliation: Department of Integrative Physiology, University of North Texas Health Science Center, Fort Worth, TX 76107, USA. xshi@hsc.unt.edu
authors.forename: Xiangrong
authors.initials: X
authors.lastname: Shi
authors.forename: Guoyuan
authors.initials: G
authors.lastname: Huang
authors.forename: Scott A
authors.initials: SA
authors.lastname: Smith
authors.forename: Rong
authors.initials: R
authors.lastname: Zhang
authors.forename: Kevin J
authors.initials: KJ
authors.lastname: Formes
mesh_terms: D000328:Adult; D000367:Age Factors; D000368:Aged; D000375:Aging; D001158:Arteries; D017704:Baroreflex; D001794:Blood Pressure; D001795:Blood Pressure Determination; D005260:Female; D006801:Humans; D007024:Hypotension, Orthostatic / Q000503:physiopathology*; D020896:Hypovolemia / Q000209:etiology / Q000503:physiopathology; D008150:Lower Body Negative Pressure; D008297:Male; D008875:Middle Aged