Voulgaris A, Nena E, Steiropoulos P. Burden of nocturnal hypoxia and type of positive airway pressure therapy may influence markers of acute kidney injury in patients with obstructive sleep apnea. J Clin Sleep Med. 2019;15(11):1695.
We read with great interest the article by Chuang et al,1 in which markers of acute kidney injury were assessed in a sample of patients with obstructive sleep apnea (OSA) before and after 6 months of continuous positive airway pressure (CPAP) treatment. During the past years, significant improvements in the understanding of the link between OSA and chronic kidney disease have been made, acknowledging that nocturnal hypoxia may stand as a risk factor for the development and progression of chronic kidney disease.2
More specifically, evidence from experimental studies suggests that intermittent hypoxia during sleep may induce kidney damage, characterized by glomerular hypertrophy and over-expression of glomerular growth factors as well as renal cellular apoptosis.3 Recent clinical studies also have underlined the significant role of nocturnal hypoxia in kidney dysfunction of patients with OSA.4,5 Taking this into consideration, it would be of significant importance if Chuang et al had provided more details on indices of hypoxia during sleep, in addition to oxygen desaturation index.
Another aspect concerning the current study,1 which needs to be reported, is the type of positive airway pressure therapy applied (fixed or auto-adjusting) to the patients with OSA. The latest data6 demonstrate that fixed CPAP is superior to auto-adjusting CPAP in terms of protecting renal function decline (assessed by the estimated glomerular filtration rate), and this is probably attributed to the greater decrease in the tone of sympathetic activity, a common characteristic of OSA and chronic kidney disease and a linking pathogenetic mechanism between them. This could also be valid for markers of acute kidney injury. Certainly, the aforementioned missing data could be used in order to shed light on this very interesting association between OSA and kidney dysfunction.
All authors have seen and approved the manuscript. The authors report no conflicts of interest.