Moderate-to-Severe Obstructive Sleep Apnea and Cognitive Function Impairment in Patients with COPD

Abstract

Xiao Lei Zhang,1– 5 Bo Gao,1– 3 Teng Han,1,2 Bo Yun Xiang,1,2 Xin Liu1,2 1Department of Pulmonary and Critical Care Medicine, Center of Respiratory Medicine, China-Japan Friendship Hospital, Beijing, People’s Republic of China; 2National Clinical Research Center for Respiratory Diseases, Beijing, People’s Republic of China; 3Capital Medical University, Beijing, People’s Republic of China; 4The Graduate School of Peking Union Medical College, Chinese Academy of Medical Science and Peking Union Medical College, Beijing, People’s Republic of China; 5Peking University Health Science Center, Beijing, People’s Republic of ChinaCorrespondence: Xiao Lei ZhangDepartment of Pulmonary and Critical Care Medicine, Center of Respiratory Medicine, China-Japan Friendship Hospital, Beijing, People’s Republic of ChinaFax [phone]Email [email protected]: Prior studies have indicated that patients with chronic obstructive pulmonary disease (COPD) exhibit significant cognitive defects on neuropsychological testing. Obstructive sleep apnea (OSA) is common in patients with COPD and is associated with reduced cognitive function; however, the combined impact of these two conditions on cognitive function is unknown. The aim of the study was to investigate the impact of OSA on cognitive impairment in patients with COPD.Methods: Sixty-five stable COPD patients aged over 60 years underwent overnight polysomnography (PSG). Global cognitive functions were evaluated using the Mini-Mental State Examination (MMSE).Results: Compared to patients with COPD alone, patients with both COPD and OSA performed worse on the MMSE (25.5± 2.9 vs 23.5± 3.2; p=0.01) and were more likely to be at risk for developing dementia based on the MMSE score (MMSE≤ 24) (31% vs 66%; p< 0.01), independent of key demographic, educational and medical variables known to affect cognitive function in COPD. COPD patients with an apnea hypopnea index (AHI) of ≥ 30 events/h had lower MMSE scores than those with an AHI of < 15 events/h. In addition to age and education level, the severity of nocturnal intermittent hypoxia is an independent predictor of the risk of dementia in patients with COPD (OR=1.24, 95% CI 1.04– 1.48, p = 0.02).Conclusion: The current findings indicate that patients with COPD with comorbid OSA may be at greater risk for global cognitive impairment relative to patients with COPD alone. The mechanisms underlying the exaggerated cognitive dysfunction seem to be related to intermittent hypoxia. Further work is needed to understand the impact of OSA on the specific domains of cognitive impairment and the therapeutic implications of OSA in COPD.Keywords: chronic obstructive pulmonary disease, obstructive sleep apnea, cognitive function

Keywords

• chronic obstructive pulmonary disease
• obstructive sleep apnea
• cognitive function