SYSTEMIC HEMODYNAMICS DURING SLEEP IN YOUNG OR MIDDLE-AGED AND ELDERLY PATIENTS WITH ESSENTIAL-HYPERTENSION

Age-related changes in cardiovascular regulatory mechanisms may affect blood pressure homeostasis during sleep and in the daytime. This stud y compared systemic hemodynamics during the daytime and sleep between 12 young or middle-aged patients (young, 42.1+/-13.9 years old, mean+/ -SD, less than 56 years old) and 12 elderly patients with essential hy pertension (old, 65.3+/-2.8, 60 to 70 years old). They were all hospit alized and placed on a diet containing approximately 7 g sodium chlori de per day. Intra-arterial blood pressure and electrocardiogram were r ecorded for 24 hours, and electroencephalogram and electroophthalmogra m were recorded during the night with st telemetric method. Cardiac ou tput was measured with patients in the supine position by the cuvette method during the daytime and stage 3 or 4 sleep at night. The average d 24-hour blood pressure was similar in the two groups (140+/-2 [SEM]/ 85+/-3 mm Hg in the young group and 144+/-4/81+/-2 mm Hg in the old gr oup). The reduction in mean blood pressure during sleep was also compa rable in both groups (-18+/-2 in the young group and -20+/-2 mm Hg in the old group). Cardiac index was smaller in the old group than the yo ung group during both the daytime and sleep (daytime, 2.3+/-0.1 versus 3.2+/-0.2 [L/min]/m(2), P<.01; sleep, 2.1+/-0.1 versus 2.6+/-0.2 [L/m in]/m(2), P<.01). The reduction in cardiac index during sleep was grea ter in the young than the old group (P<.05). Total peripheral Vascular resistance index was elevated in the old group compared with the youn g group (daytime, 47.1+/-1.8 versus 36.2+/-2.6 mm Hg.min m(2)/L, P<.01 ; sleep, 41.4+/-2.4 versus 36.1+/-2.1, mm Hg.min m(2)/L, P<.05). Altho ugh the reduction in total peripheral vascular resistance index during sleep was not significant in the young group, it was pronounced in th e bid group, showing a significant group difference (P<.001). These fi ndings indicate that different hemodynamic components are involved in the reduction of blood pressure during sleep in young and old hyperten sive patients.