title: Effect of aging on carotid artery stiffness and baroreflex sensitivity during head-out water immersion in man.
abstract: To examine the possible age-related blood pressure (BP) deregulation in response to central hypervolemia, we measured spontaneous baroreflex sensitivity (SBRS), carotid arterial compliance (CC), and R-R interval coefficient of variation (RRICV) during basal and thermoneutral resting head-out-of-water immersion (HOWI) in 7 young (YG = 24.0 +/- 0.8 years) and 6 middle-aged/older (OL = 59.3 +/- 1.3 years) healthy men. Compared with basal conditions (YG = 19.6 +/- 4.0 vs OL = 6.1 +/- 1.5 ms/mmHg, P < 0.05), SBRS remained higher in YG than OL during rest HOWI (YG = 23.6 +/- 6.6 vs OL = 9.3 +/- 2.1 ms/mmHg, P < 0.05). The RRICV was significantly different between groups (YG = 6.5 +/- 1.4 vs OL = 2.8 +/- 0.4%, P < 0.05) under HOWI. The OL group had no increase in CC, but a significant increase in systolic BP (basal = 115.3 +/- 4.4 vs water = 129.3 +/- 5.3 mmHg, P < 0.05) under HOWI. In contrast, the YG group had a significant increase in CC (basal = 0.16 +/- 0.01 vs water = 0.17 +/- 0.02 mm(2)/mmHg, P < 0.05) with no changes in systolic BP. SBRS was positively related to CC (r = 0.58, P < 0.05 for basal vs r = 0.62, P < 0.05 for water). Our data suggest that age-related vagal dysfunction and reduced CC may be associated with SBRS differences between YG and OL groups, and with BP elevation during HOWI in healthy older men.
authors.affiliation: Instituto do Coração, Faculdade de Medicina, Universidade de São Paulo, São Paulo, SP, Brasil. lindabrz@hotmail.com
authors.forename: L M
authors.initials: LM
authors.lastname: Ueno
authors.forename: M
authors.initials: M
authors.lastname: Miyachi
authors.forename: T
authors.initials: T
authors.lastname: Matsui
authors.forename: K
authors.initials: K
authors.lastname: Takahashi
authors.forename: K
authors.initials: K
authors.lastname: Yamazaki
authors.forename: K
authors.initials: K
authors.lastname: Hayashi
authors.forename: S
authors.initials: S
authors.lastname: Onodera
authors.forename: T
authors.initials: T
authors.lastname: Moritani
mesh_terms: D000328:Adult; D000367:Age Factors; D000368:Aged; D000375:Aging / Q000502:physiology*; D017704:Baroreflex / Q000502:physiology*; D001794:Blood Pressure / Q000502:physiology; D002339:Carotid Arteries / Q000033:anatomy & histology / Q000502:physiology*; D004562:Electrocardiography; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D020896:Hypovolemia; D007101:Immersion; D008297:Male; D008875:Middle Aged; D012146:Rest / Q000502:physiology*