Ventilatory and arousal patterns during sleep in normal young and elderly subjects

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Abstract
Since elderly subjects have lower chemosensitivity, we postulated that ventilation might be more state dependent in the elderly. To address this we investigated the changes in ventilation, measured by respiratory plethysmography, with sleep in 12 healthy young (19-29 yr) and 13 elderly (> 65 yr) subjects. Ventilation was measured in representative periods in each sleep state. These data showed that there is no difference between the elderly and the young either in mean ventilation or in the variability of ventilation awake or in the different states of sleep. In both groups ventilation was variable in stage 1-2 sleep and least variable in stage 3-4 sleep. The variability in stage 1-2 sleep was due to periodic breathing (cycle time .apprx. 45 s) in both age groups. Although within a sleep state no differences were observed, over the night of study the elderly behaved differently from the young. Apneas occurred more frequently in the elderly, and 5 of 13 elderly met the criteria for sleep apnea syndrome compared with 1 of 12 young subjects. Apneas tended to occur predominately in stage 1-2 sleep and seem to be an exaggeration of the periodicity that is typical of this state. Four of the elderly with apnea remained in this stage of sleep throughout the night of study. The apneic episodes usually terminated with an electroencephalogram arousal that occurred prior to or simultaneously with the onset of ventilation. Transient arousals were more frequent in the elderly (21.6 arousals/h) than in the young (7.2 arousals/h) (P < 0.01); however, there was no difference in the number of transient arousals in those elderly with and without sleep apnea. In conclusion, although mean ventilation did not differ between the young and the elderly in the different stages of sleep, periodic apneas occurred more frequently in the elderly during light sleep.