Ageing does not influence the sleep-related decrease in the hypercapnic ventilatory response

In young people, a sleep-related reduction in the gain of the ventilatory chemoreflex feedback loop occurs; in the elderly, it has been reported that no sleeprelated reduction occurs. A relatively high loop gain could contribute to periodic breathing and central sleep apnoea in the elderly. This study tested the hypothesis that ageing is associated with a reduction in the magnitude of the sleep-related decrease in the hypercapnic ventilatory response (HCVR). The HCVR was measured using a steady state method, awake and asleep, in groups (n=10) of elderly (66-81 yrs) and young (23-35 yrs) nonapnoeics. Upper airway resistance was maintained close to wakefulness levels using continuous positive airway pressure (mean sleep-related increase in resistance: elderly 1.6+/-1.2 cmH(2)O(.)L(.)s(-1), young 1.2+/-0.8 cmH(2)O(.)L(.)s(-1)). The sleep-related decrease in the HCVR was similar in the elderly and young groups (elderly: wake 0.14+/-0.06 and sleep 0.06+/-0.02 L(.)min(-1.)kPa and young, wake 0.19+/-0.07 and sleep 0.10+/-0.04 L(.)min(-1.)kPa). Ageing per se was shown not to change the magnitude of the sleep-related decrease in hypercapnic ventilatory response. The authors speculate that age-related changes in the hypercapnic ventilatory response are unlikely to contribute to the increased prevalence of central sleep apnoea in the elderly.