Physiological adaptation to high-altitude living in native Andeans is unlikely to compensate for the significant differences we observed between diurnal and nocturnal oxyhemoglobin saturation, most marked in infancy. This vulnerability to sleep-related hypoxia in early childhood has potential lifespan implications. Future studies should characterize the sleep- related respiratory physiology underpinning our observations.

HA native Andean children have more respiratory events when scoring relies on SpO2 desaturation due to inherent SpO2 instability. Use of American Academy of Sleep Medicine scoring criteria may yield false-positive results for obstructive sleep-disordered breathing at HA.

BackgroundSleep apnea is common and associated with poor outcome in severe chronic kidney disease, but validated screening tools are not available. Our objectives were to determine the prevalence of sleep apnea in this population, to assess the validity of screening for sleep apnea using an ApneaLink device and to investigate the relationship of sleep apnea to; symptoms, spirometry and body water.MethodsPatients with glomerular filtration rate ≤30 mL/min/1.73 m2, whether or not they were receiving haemodialysis, were eligible for enrolment. Participants completed symptom questionnaires, performed an ApneaLink recording and had total body water measured using bioimpedance. This was followed by a multi-channel polysomnography recording which is the gold-standard diagnostic test for sleep apnea.ResultsFifty-seven participants were enrolled and had baseline data collected, of whom only 2 did not have sleep apnea. An apnea hypopnea index ≥30/h was found in 66% of haemodialysis and 54% of non-dialysis participants. A central apnea index ≥5/h was present in 11 patients, with only one dialysis patient having predominantly central sleep apnea. ApneaLink underestimated sleep apnea severity, particularly in the non-dialysis group. Neither total body water corrected for body size, spirometry, subjective sleepiness nor overall symptom scores were associated with sleep apnea severity.ConclusionsThis study demonstrates a very high prevalence of severe sleep apnea in patients with chronic kidney disease. Sleep apnea severity was not associated with quality of life or sleepiness scores and was unrelated to total body water corrected for body size. Routine identification of sleep apnea with polysomnography rather than screening is more appropriate in this group due to the high prevalence.Electronic supplementary materialThe online version of this article (doi:10.1186/s12882-017-0544-3) contains supplementary material, which is available to authorized users.

In early childhood, conductive hearing loss mediates the relationship between SDB, irrespective of severity, and parent report of executive function but not behaviour. Treatment of hearing loss in pre-school SDB might improve executive function.

We confirmed previous findings of a stage-dependent modulation of HRV in Andean children living at both high and low altitudes. Moreover, we showed subtle alteration of HRV in sleep in HA children, with intriguing differences in the very low frequency domain during REM sleep. Whether these differences are the results of an adaptation to high altitude living, or an indirect effect of differences in oxyhaemoglobin saturation remain unclear, and further research is required to address these questions.