Hemodynamics in the Untreated Hypertensive Elderly: Implications for Gender Differences

BACKGROUND: Previous studies have shown that elderly women have a higher prevalence of hypertension and lower blood pressure (BP) control rate than elderly men, but the underlying mechanisms are unclear. We tested the hypothesis that hemodynamic regulation of BP would be different between genders in elderly hypertensives. METHODS: We studied 20 sedentary, untreated hypertensive patients (15 men and 5 women, age range 60-85) and 4 age-matched normotensive women. Twenty-four hour ambulatory BP was monitored (ABPM). Supine hemodynamics, including arm BP (SunTech), heart rate (HR, ECG), cardiac output (Qc, C2H2 rebreathing), stroke volume (SV=Qc/HR), stroke index (SI=SV/body surface area), and total peripheral resistance (TPR=mean BP/Qc) were measured. Blood/plasma volume (BV/PV) was determined by a modified carbon monoxide rebreathing technique. RESULTS: ABPM results showed higher values in patients than controls, but did not differ between genders (mean±SD, 140±8/78±8 mmHg; 141±10/80±6 for hypertensive women and men versus 119±7/71± 4 for normotensive women). Supine resting HR was not different between patients and controls (P = 0.15) or between genders (P = 0.20). Supine TPR was greater in hypertensive women than men (2133±633 dyn·s·cm-5 and 1619±325 respectively, P=0.04), but was not clearly different in hypertensive versus normotensive women (2252±562, P = 0.01). Indeed, TPR was higher in normotensive women than hypertensive men (P = 0.01), emphasizing the importance of this variable for gender differences in BP. SI was markedly higher in hypertensive men (36±7 mL/m2) but significantly lower in hypertensive women (32±5). Also of note, normalized blood volumes were lower in hypertensive women (61±7 mL/kg) than men (70±6) and lowest in normotensive women (56±5). CONCLUSIONS: These results suggest that there is an inherent difference in hemodynamic control of BP between genders in elderly hypertension. A greater peripheral vascular resistance may contribute to a higher prevalence of hypertension in elderly women. Conversely, in elderly men hypertension may be linked to a higher stroke volume.