Nocturnal Sleep Breathing Patterns in Healthy Adolescents Residing at Very High Altitudes in Bolivia.

Data on sleep and respiratory patterns among adolescents residing at very high altitude (> 3500 m) remain scarce, and altitude-related physiological differences may influence these parameters. Studying adolescents at different very high altitudes is crucial, as subtle environmental variations could affect sleep-related oxygenation and respiratory function. This study aimed to characterise sleep-related oxygenation and respiratory parameters in healthy adolescents native to two distinct very high-altitude environments. Overnight sleep polygraphy was performed in 163 healthy adolescents aged 13.5 to < 18 years living in La Paz (3620 m) and El Alto (4060 m), Bolivia. Mean nocturnal oxygen saturation, oxygen desaturation index, and apnea-hypopnea index were assessed alongside subjective sleep quality, morning blood pressure, heart rate, haemoglobin concentration, and Epworth Sleepiness Scale scores. Adolescents at 4060 m had significantly lower mean nocturnal oxygen saturation (84.8% ± 2.2%) compared with those at 3620 m (87.8% ± 1.8%), and a higher oxygen desaturation index (21.2 ± 8.5/h vs. 17.1 ± 9.0/h). The apnea-hypopnea index did not differ significantly between altitudes (6.2 ± 4.8/h vs. 5.6 ± 4.6/h). At 3620 m, females showed lower oxygen desaturation and apnea-hypopnea indices compared with males. Despite the more pronounced nocturnal hypoxemia at 4060 m, haemoglobin concentration did not increase, suggesting limited haematological compensation. Subjective sleep quality, blood pressure, and heart rate were similar between both altitude groups. Healthy adolescents living chronically at very high altitude exhibit altitude-dependent reductions in nocturnal oxygenation and increased desaturation frequency, without evidence of sleep-disordered breathing. These findings underscore the need for altitude-specific normative values to support accurate interpretation of sleep studies in high-altitude populations.