Does reduced vascular stiffening fully explain preserved cardiovagal baroreflex function in older, physically active men?

• Published in: Circulation (New York, N.Y.) N.Y.), 2001-05, Vol.103 (20), p.2424-2427
• Main Authors: HUNT, Brian E, FARQUHAR, William B, TAYLOR, J. Andrew
• Format: Article
• Language: English
• Subjects: Adult; Aged; Aging - physiology; Analysis of Variance; Baroreflex - physiology; Biological and medical sciences; Blood Pressure - physiology; Blood Vessels - physiology; Exercise - physiology; Exercise Test; Fundamental and applied biological sciences. Psychology; Heart; Humans; Male; Middle Aged; Physical Endurance - physiology; Vagus Nerve - physiology; Vascular Resistance - physiology; Vertebrates: cardiovascular system
• ISSN: 0009-7322; 1524-4539
• DOI: 10.1161/01.cir.103.20.2424

We measured cardiovagal baroreflex gain and its vascular mechanical and neural components during dynamic baroreflex engagement in 10 young untrained men, 6 older untrained men, and 12 older, physically active men. Our newly developed assessment of beat-to-beat carotid diameters during baroreflex engagement estimates the mechanical transduction of pressure into barosensory stretch (diameter/pressure), the neural transduction of stretch into vagal outflow (R-R interval/diameter), and conventional integrated cardiovagal baroreflex gain (R-R interval/pressure). Integrated gain was lower in older untrained men than in young untrained men (6.8+/-1.2 versus 15.7+/-1.8 ms/mm Hg) due to both lower mechanical (9.1+/-1.0 versus 17.1+/-2.4 mm Hg/microm) and lower neural (0.57+/-0.10 versus 0.90+/-0.10 ms/microm) transduction. Integrated gain in older active men (13.3+/-2.7 ms/mm Hg) was comparable to that in young untrained men. This was achieved through mechanical transduction (12.1+/-1.4 mm Hg/microm) that was modestly higher than that in older untrained men and neural transduction (1.00+/-0.20 ms/microm) comparable to that in young untrained men. Across groups, both mechanical and neural components were related to integrated gain; however, the neural component carried greater predictive weight (beta=0.789 versus 0.588). Both vascular and neural deficits contribute to age-related declines in cardiovagal baroreflex gain; however, long-term physical activity attenuates this decline by maintaining neural vagal control.