Effect of altitude and acetazolamide on sleep and nocturnal breathing in healthy lowlanders 40 y of age or older. Data from a randomized trial

Study Objectives To assess altitude-induced sleep and nocturnal breathing disturbances in healthy lowlanders 40 y of age or older and the effects of preventive acetazolamide treatment. Methods Clinical examinations and polysomnography were performed at 760 m and in the first night after ascent to 3100 m in a subsample of participants of a larger trial evaluating altitude illness. Participants were randomized 1:1 to treatment with acetazolamide (375 mg/day) or placebo, starting 24 h before and while staying at 3100 m. The main outcomes were indices of sleep structure, oxygenation, and apnea/hypopnea index (AHI). Results Per protocol analysis included 86 participants (mean +/- SE 53 +/- 7 y old, 66% female). In 43 individuals randomized to placebo, mean nocturnal pulse oximetry (SpO(2)) was 94.0 +/- 0.4% at 760 m and 86.7 +/- 0.4% at 3100 m, with mean change (95%CI) -7.3% (-8.0 to -6.5); oxygen desaturation index (ODI) was 5.0 +/- 2.3 at 760 m and 29.2 +/- 2.3 at 3100 m, change 24.2/h (18.8 to 24.5); AHI was 11.3 +/- 2.4/h at 760 m and 23.5 & PLUSMN; 2.4/h at 3100 m, change 12.2/h (7.3 to 17.0). In 43 individuals randomized to acetazolamide, altitude-induced changes were mitigated. Mean differences (delta, 95%CI) in altitude-induced changes were: delta SpO(2) 2.3% (1.3 to 3.4), delta ODI -15.0/h (-22.6 to -7.4), delta AHI -11.4/h (-18.3 to -4.6). Total sleep time, sleep efficiency, and N3-sleep fraction decreased with an ascent to 3100 m under placebo by 40 min (17 to 60), 5% (2 to 8), and 6% (2 to 11), respectively. Acetazolamide did not significantly change these outcomes. Conclusions During a night at 3100 m, healthy lowlanders aged 40 y or older revealed hypoxemia, sleep apnea, and disturbed sleep. Preventive acetazolamide treatment improved oxygenation and nocturnal breathing but had no effect on sleep duration and structure.