Influence of Obstructive Sleep Apnea on Cognitive Impairment in Patients With COPD

Abstract

We read with great interest the recent article in CHEST (December 2012) by Villeneuve et al1Villeneuve S Pepin V Rahayel S et al.Mild cognitive impairment in moderate to severe COPD: a preliminary study.Chest. 2012; 142: 1516-1523Abstract Full Text Full Text PDF PubMed Scopus (131) Google Scholar entitled “Mild Cognitive Impairment in Moderate to Severe COPD: A Preliminary Study.” In their article, Villeneuve et al1Villeneuve S Pepin V Rahayel S et al.Mild cognitive impairment in moderate to severe COPD: a preliminary study.Chest. 2012; 142: 1516-1523Abstract Full Text Full Text PDF PubMed Scopus (131) Google Scholar demonstrated that 36% of patients with COPD had mild cognitive impairment (MCI), compared with 12% of healthy subjects. The authors took great care to exclude from the study all patients who presented comorbidities that could affect cognitive function. With regard to the comorbidities associated with COPD, we would like to highlight the important role of obstructive sleep apnea (OSA). Indeed, it was appreciated by several well-controlled epidemiologic studies that about 20% of subjects with OSA will have COPD,2Fletcher EC Chronic lung disease in the sleep apnea syndrome.Lung. 1990; 168: 751-761Crossref PubMed Scopus (33) Google Scholar and about 10% of OSA is disclosed among patients with COPD independently of the degree of functional status.3Chaouat A Weitzenblum E Krieger J Ifoundza T Oswald M Kessler R Association of chronic obstructive pulmonary disease and sleep apnea syndrome.Am J Respir Crit Care Med. 1995; 151: 82-86Crossref PubMed Scopus (385) Google Scholar There is evidence that OSA has an active role in the development of cognitive impairment.4Sforza E Roche F Sleep apnea syndrome and cognition.Front Neurol. 2012; 3: 87Crossref PubMed Scopus (91) Google Scholar In this regard, in the study of Villeneuve et al,1Villeneuve S Pepin V Rahayel S et al.Mild cognitive impairment in moderate to severe COPD: a preliminary study.Chest. 2012; 142: 1516-1523Abstract Full Text Full Text PDF PubMed Scopus (131) Google Scholar an intriguing finding is the slight (although not significant) increase in the Epworth Sleepiness Scale among patients with COPD and MCI compared with patients with COPD but without MCI, which may lead one to hypothesize the presence of a proportion of patients with OSA among subjects with COPD and MCI. The primary mechanisms underlying cognitive impairment in OSA are represented by nocturnal hypoxemia, sleep fragmentation, and daytime sleepiness4Sforza E Roche F Sleep apnea syndrome and cognition.Front Neurol. 2012; 3: 87Crossref PubMed Scopus (91) Google Scholar; large studies suggest that hypoxemia is responsible for frontal impairment and executive dysfunction, while sleep fragmentation and daytime sleepiness influence attention.4Sforza E Roche F Sleep apnea syndrome and cognition.Front Neurol. 2012; 3: 87Crossref PubMed Scopus (91) Google Scholar In patients with COPD, hypoxemia, hypercapnia, and vascular comorbidities may be a cause of cognitive alterations.1Villeneuve S Pepin V Rahayel S et al.Mild cognitive impairment in moderate to severe COPD: a preliminary study.Chest. 2012; 142: 1516-1523Abstract Full Text Full Text PDF PubMed Scopus (131) Google Scholar Therefore, in patients with COPD and OSA (overlap syndrome), there is the possibility that all the aforesaid mechanisms operate simultaneously and/or synergistically. In this regard, it is widely accepted that patients with overlap syndrome develop more pronounced, nocturnal, oxygen desaturation than those with COPD or OSA alone.3Chaouat A Weitzenblum E Krieger J Ifoundza T Oswald M Kessler R Association of chronic obstructive pulmonary disease and sleep apnea syndrome.Am J Respir Crit Care Med. 1995; 151: 82-86Crossref PubMed Scopus (385) Google Scholar Furthermore, there is evidence that subjects with overlap syndrome show more severe diurnal hypoxemia compared with patients with OSA.5Lacedonia D Carpagnano GE Aliani M et al.Daytime PaO(2) in OSAS, COPD and the combination of the two (overlap syndrome).Respir Med. 2013; 107: 310-316Abstract Full Text Full Text PDF PubMed Scopus (31) Google Scholar For all these reasons, we would like to stimulate discussion about the need to consider the presence of OSA among patients with COPD who have cognitive impairment.