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David D. M. Nicholl, BHSc; Sofia B. Ahmed, MD; Andrea H. S. Loewen, MD; Brenda R. Hemmelgarn, MD, PhD; Darlene Y. Sola, RN; Jaime M. Beecroft, MSc; Tanvir C. Turin, MBBS, PhD; Patrick J. Hanly, MD
Author and Funding Information

From the Department of Medicine (Mr Nicholl; Drs Ahmed, Loewen, Hemmelgarn, Turin, and Hanly; and Ms Sola), Faculty of Medicine, and Sleep Centre (Drs Loewen and Hanly and Mr Beecroft), Foothills Medical Centre, University of Calgary.

Correspondence to: Patrick J. Hanly, MD, 1421 Health Sciences Centre, 3330 Hospital Dr NW, Calgary, AB, T2N 4Z5, Canada; e-mail: phanly@ucalgary.ca


Financial/nonfinancial disclosures: The authors have reported to CHEST that no potential conflicts of interest exist with any companies/organizations whose products or services may be discussed in this article.

Reproduction of this article is prohibited without written permission from the American College of Chest Physicians. See online for more details.


Chest. 2012;142(4):1076-1077. doi:10.1378/chest.12-1482
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To the Editor:

We agree with Dr Mirrakhimov that age, obesity, and comorbidities such as congestive heart failure and cerebrovascular disease are recognized risk factors for the development of obstructive sleep apnea. In addition, chronic medical disorders, such as COPD, may cause nocturnal hypoxia. In view of this, we surveyed patients for these risk factors and found that those with chronic kidney disease (CKD) and end-stage renal disease (ESRD) generally were older and heavier and had a higher prevalence of these comorbidities.1 Consequently, we performed a multivariate analysis to determine how much these risk factors and kidney function status contributed to the increased prevalence of sleep apnea and nocturnal hypoxia. We found that although age, BMI, and neck circumference were associated with sleep apnea, kidney function status, reflected by ESRD, was also associated with the presence of sleep apnea independently of other traditional risk factors for obstructive sleep apnea. Furthermore, we found that CKD was associated with the presence of nocturnal hypoxia independently of COPD. Notwithstanding the limitations of our cross-sectional design or residual confounding due to unmeasured factors, these findings suggest that chronic kidney failure contributes significantly to the pathogenesis of sleep apnea and nocturnal hypoxia in this patient population.

The underlying mechanisms responsible for the association between kidney failure and sleep apnea and nocturnal hypoxia are not clear and require further investigation. Our study did not address this issue. A relationship between rostral displacement of fluid from the legs and the apnea-hypopnea time was recently described in patients with ESRD.2 This supports one of the potential mechanisms we discussed, namely that fluid overload may play a role independently of the other aforementioned risk factors. We have previously found in a longitudinal study that nocturnal hypoxia is associated with accelerated loss of kidney function.3 Consequently, the relationship between nocturnal hypoxia and CKD may be bidirectional, with one exacerbating the other. Regardless, the presence of nocturnal hypoxia in CKD represents a potential target for future interventional studies that may improve several important clinical outcomes.4

Finally, portable monitoring was performed following the current American Academy of Sleep Medicine guidelines and was analyzed by a sleep medicine physician.5 We have acknowledged the limitations of portable monitoring and the steps we took to minimize their potential impact on the study findings, which we do not believe is significant. We agree that well-designed, longitudinal studies are required to further evaluate the relationship between kidney function and the development of sleep apnea and nocturnal hypoxia.

Nicholl DDM, Ahmed SB, Loewen AHS, et al. Declining kidney function increases the prevalence of sleep apnea and nocturnal hypoxia. Chest. 2012;141(6):1422-1430. [PubMed] [CrossRef]
 
Elias RM, Bradley TD, Kasai T, Motwani SS, Chan CT. Rostral overnight fluid shift in end-stage renal disease: relationship with obstructive sleep apnea. Nephrol Dial Transplant. 2012;27(4):1569-1573.
 
Ahmed SB, Ronksley PE, Hemmelgarn BR, et al. Nocturnal hypoxia and loss of kidney function. PLoS ONE. 2011;6(4):e19029.
 
James MT, Hemmelgarn BR, Tonelli M. Early recognition and prevention of chronic kidney disease. Lancet. 2010;375(9722):1296-1309.
 
Collop NA, Anderson WM, Boehlecke B, et al. Portable Monitoring Task Force of the American Academy of Sleep Medicine. Clinical guidelines for the use of unattended portable monitors in the diagnosis of obstructive sleep apnea in adult patients. J Clin Sleep Med. 2007;3(7):737-747.
 

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References

Nicholl DDM, Ahmed SB, Loewen AHS, et al. Declining kidney function increases the prevalence of sleep apnea and nocturnal hypoxia. Chest. 2012;141(6):1422-1430. [PubMed] [CrossRef]
 
Elias RM, Bradley TD, Kasai T, Motwani SS, Chan CT. Rostral overnight fluid shift in end-stage renal disease: relationship with obstructive sleep apnea. Nephrol Dial Transplant. 2012;27(4):1569-1573.
 
Ahmed SB, Ronksley PE, Hemmelgarn BR, et al. Nocturnal hypoxia and loss of kidney function. PLoS ONE. 2011;6(4):e19029.
 
James MT, Hemmelgarn BR, Tonelli M. Early recognition and prevention of chronic kidney disease. Lancet. 2010;375(9722):1296-1309.
 
Collop NA, Anderson WM, Boehlecke B, et al. Portable Monitoring Task Force of the American Academy of Sleep Medicine. Clinical guidelines for the use of unattended portable monitors in the diagnosis of obstructive sleep apnea in adult patients. J Clin Sleep Med. 2007;3(7):737-747.
 
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