Arterial stiffness during whole-body passive heat stress in healthy older adults

We tested the hypothesis that whole-body passive heat stress reduces arterial stiffness in older adults. At preheat stress (baseline) and when core temperature was elevated by 0.6 +/- 0.2 degrees C (mild) and 1.2 +/- 0.3 degrees C (moderate), arterial stiffness was measured in eight healthy younger (26 +/- 5 years) and eight healthy older (70 +/- 4 years) adults in the supine position. Arterial stiffness was estimated from carotid-to-femoral pulse wave velocity (cfPWV, applanation tonometry). cfPWV was higher at baseline in older adults (8.8 +/- 2.3 m/ sec vs. 5.6 +/- 0.9 m/sec, P < 0.01) and this difference was maintained throughout passive heat stress (P < 0.01). cfPWV did not change (P = 0.49) with passive heat stress in either younger (at moderate heat stress: 6.0 +/- 1.0 m/sec) or older (at moderate heat stress: 8.5 +/- 1.6 m/sec) adults. However, the influence of baseline cfPWV on the change in cfPWV during mild (r = +/- 0.66, P = 0.04) and moderate (r = +/- 0.87, P < 0.01) heat stress were inversely related in older adults, and the strength of these relations was not statistically different (P = 0.08). In younger adults, the influence of baseline cfPWV on the change in cfPWV during mild heat stress was also inversely related (r = +/- 0.79, P = 0.01), while the strength of this relation was attenuated at moderate heat stress (r = +/- 0.24, P = 0.30). Changes in arterial stiffness during passive heat stress in adults aged = 65 year are likely dependent on the magnitude of baseline arterial stiffness and not necessarily age.