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 remains equivocal. Forty-three young (21 +/- 1yr, means +/- SE) men (YM, n = 20) and women (YW, n = 23) and 16 older (60 +/- 1yr) 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- to 5-min baseline and 2-min CPT. Baseline mean arterial pressure (MAP) was greater in OM than in YM (92 +/- 4 vs. 77 +/- 1 mmHg, P < 0.01), but similar in women (P = 0.12). Baseline MSNA incidence was greater in OM [69 +/- 6 bursts/100 heartbeats (hb)] than in OW (44 +/- 7 bursts/100 hb, P = 0.02) and lower in young adults (YM: 17 +/- 3 vs. YW: 16 +/- 2 bursts/100 hb. P < 0.01), but similar across the sexes (P = 0.83). However, when exposed to the CPT. MSNA increased more rapidly in OW (Delta 43 +/- 6 bursts/100 hb; group x time, P = 0.01) compared with OM (Delta 15 +/- 3 bursts/100 hb) but was not different between YW (Delta 30 +/- 3 bursts/100 hb) and YM (Delta 33 +/- 4 bursts/100 hb, P = 1.0). There were no differences in MAP with CPT between groups (group x 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.