Effect of aging on sleep-related changes in respiratory variables

Several respiratory variables were examined in 11 healthy elderly (greater than 60 years) and 12 younger (30-39 years) control subjects during all-night sleep runs, with a view to determining the effect of the aging process on breathing during sleep. O2 saturation, end-tidal PCO2, and transcutaneous PCO2 were monitored, together with standard sleep staging measures. Estimates of tidal volume (Vt) and ventilation (Ve) were obtained using a Respitrace inductive plethysmography system, from which respiratory rate (fb) was also measured. Older subjects had more sleep apnea/hypopnea than younger subjects, an incidence of 55 versus 8%, respectively. More of their arousals were associated with respiratory disturbance than those of the younger subjects, and they had more brief, but not longer, arousals. Mean O2 saturation was lower in older subjects during wakefulness but did not decrease more in older subjects than in control subjects during sleep. Mean end-tidal/transcutaneous PCO2 did not differ between groups during wakefulness or sleep. Vt and Ve estimates did not decrease during slow wave sleep in older subjects as they did in the younger subjects. It was concluded that aging by itself does not significantly alter average sleep-related changes in O2 saturation or PCO2, although the increased incidence of respiratory disturbance does produce transient swings in these variables. The lack of a decrease in ventilation estimates during sleep in spite of the usual changes in O2 saturation and PCO2 in the older group indicates a possible decrease in effective gas exchange.