Aging is associated with increased propensity for central apnea during NREM sleep

The reason for increased sleep-disordered breathing with predominance of central apneas in the elderly is unknown. We hypothesized that the propensity to central apneas is increased in older adults, manifested by a reduced carbon-dioxide (CO2) reserve in older compared with young adults during non-rapid eye movement sleep. Ten elderly and 15 young healthy adults underwent multiple brief trials of nasal noninvasive positive pressure ventilation during stable NREM sleep. Cessation of mechanical ventilation (MV) resulted in hypocapnic central apnea or hypopnea. The CO2 reserve was defined as the difference in end-tidal CO2 (PETCO2) between eupnea and the apneic threshold, where the apneic threshold was PETCO2 that demarcated the central apnea closest to the eupneic PETCO2. For each MV trial, the hypocapnic ventilatory response (controller gain) was measured as the change in minute ventilation (V-E) during the MV trial for a corresponding change in PETCO2. The eupneic PETCO2 was significantly lower in elderly vs. young adults. Compared with young adults, the elderly had a significantly reduced CO2 reserve (-2.6 +/- 0.4 vs. -4.1 +/- 0.4 mmHg, P = 0.01) and a higher controller gain (2.3 +/- 0.2 vs. 1.4 +/- 0.2 l.min(-1).mmHg(-1), P = 0.007), indicating increased chemoresponsiveness in the elderly. Thus elderly adults are more prone to hypocapnic central apneas owing to increased hypocapnic chemoresponsiveness during NREM sleep. NEW & NOTEWORTHY The study describes an original finding where healthy older adults compared with healthy young adults demonstrated increased breathing instability during non-rapid eye movement sleep, as suggested by a smaller carbon dioxide reserve and a higher controller gain. The findings may explain the increased propensity for central apneas in elderly adults during sleep and potentially guide the development of pathophysiology-defined personalized therapies for sleep apnea in the elderly.