Cardiovascular function during sleep of active older adults and the effects of exercise.

Cardiovascular function during sleep was studied in 14 (6 males, 8 females) healthy, active, older adults (57-70) years). Noninvasive measures of stroke volume (SV), heart rate (HR), cardiac output (CO), pre-ejection period (PEP), and left ventricular ejection time (LVET) were taken using impedance cardiography and computer-based "ensemble" averaging. Data were obtained from the last of three nights of normal sleep and on a night following an hour walk on a treadmill at 60% VO2 max. Cardiovascular measures revealed patterns during sleep which parallel those seen in younger subjects, i.e. a progressive decline in SV and CO, unaffected by EEG sleep stage. The trend was different for heart rate, which showed only an initial decline at sleep onset. No consistent trends were seen for LVET, whereas PEP declined to a low point 1.5 h after sleep onset. Following exercise, HR was slightly elevated during the first 3 h of sleep. In contrast, SV and CO were reduced during the period of sleep between 1 and 4 h after sleep onset; this difference was observed primarily in the women (N = 8). The results suggest that an acute increase in daily activity of older adults induces only minor changes in nocturnal cardiac function.