Impact of age and sex on neural cardiovascular responsiveness to cold pressor test in humans.

Prior longitudinal work suggests that blood pressure (BP) reactivity to the cold pressor test (CPT) helps predict hypertension, yet the impact of age and sex on hemodynamic and neural responsiveness to CPT remain equivocal. Forty-three young (21±1yrs, mean±SEM) men (YM, n=20) and women (YW, n=23), and 16 older (60±1yrs) men (OM, n=9) and women (OW, n=7), participated in an experimental visit where continuous BP (finger plethysmography) and muscle sympathetic nerve activity (MSNA; microneurography) were recorded during a 3-5min baseline and 2-min CPT. Baseline mean arterial pressure (MAP) was greater in older men compared with young men, (92±4 vs. 77±1mmHg, p<0.01), but similar in women (p=0.12). Baseline MSNA incidence was greater in OM (69±6bursts/100hb) compared with OW (44±7bursts/100hb, p=0.02), and lower in young adults (YM: 17±3 vs. YW: 16±2bursts/100hb, p<0.01), but similar across sexes (p=0.83). However, when exposed to the CPT, MSNA increased more rapidly in OW (Δ43±6bursts/100hb; group×time, p=0.01) compared with OM (Δ15±3bursts/100hb), but was not different between YW (Δ30±3bursts/100hb) and YM (Δ33±4 bursts/100hb, p=1.0). There were no differences in MAP with CPT between groups (group×time, p=0.33). These findings suggest that OW demonstrate a more rapid initial rise in MSNA responsiveness to a CPT compared with OM. This greater sympathetic reactivity in OW may be a contributing mechanism to the increased hypertension risk in postmenopausal women.