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°C (mild) and 1.2 ± 0.3°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 (cf PWV , applanation tonometry). cf PWV 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). cf PWV 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 cf PWV on the change in cf PWV 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 cf PWV on the change in cf PWV 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.