title: The relationship between sleep quality and functional exercise capacity in COPD.
abstract: BACKGROUND
  Poor sleep is often associated with a series of health problems in patients with chronic obstructive pulmonary disease (COPD), but the relationship between sleep quality and functional exercise capacity has not been previously investigated.
  
  
  OBJECTIVE
  To evaluate the relationship between quality of sleep and functional exercise capacity in clinically stable COPD.
  
  
  METHODS
  One hundred three consecutive subjects with stable COPD were recruited. The subjects were assessed with the Pittsburgh Sleep Quality Index (PSQI) and divided into poor sleep group (PSQI >5) and good sleep group (PSQI ≤5). Subjects were also assessed with spirometry, 6-min walk distance (6MWD), oxygen saturation (SP O2 ), the Epworth Sleepiness Scale, Hamilton Depression Rating Scale, Hamilton Anxiety Rating Scale, COPD Assessment Test (CAT), Modified Medical Research Council dyspnea scale and quadriceps muscle function.
  
  
  RESULTS
  Poor sleep was present in 43.69% of the patients with COPD. Subjects with poor sleep had shorter 6MWD (t = -3.588, P < 0.001), greater age (t = 2.519, P = 0.013), worse quality of life (t = 5.487, P < 0.001) and more depression (t = 6.576, P < 0.001) or anxiety (t = 4.245, P < 0.001) symptoms. 6MWD showed significant negative correlations with the PSQI global score (r = -0.373, P < 0.001). Multiple stepwise regresion analysis showed that PSQI global score was an independent psychological predictor of 6MWD, and 6MWD was the only physical predictor of PSQI total score in patients with COPD.
  
  
  CONCLUSIONS
  There is a close relationship between sleep quality and functional exercise capacity in patients with COPD.
authors.affiliation: Department of Respiratory Diseases, Sun Yat-sen Memorial Hospital, Sun Yat-sen University, Guangzhou, China.
authors.forename: Rui
authors.initials: R
authors.lastname: Chen
authors.affiliation: Department of Respiratory Diseases, Sun Yat-sen Memorial Hospital, Sun Yat-sen University, Guangzhou, China.
authors.forename: Jing-Wei
authors.initials: JW
authors.lastname: Tian
authors.affiliation: The State Key Laboratory of Respiratory Disease, Guangzhou Institute of Respiratory Disease, Guangzhou Medical University, Guangzhou, China.
authors.forename: Lu-Qian
authors.initials: LQ
authors.lastname: Zhou
authors.affiliation: Department of Respiratory Diseases, Zhujiang Hospital, Southern Medical University, Guangzhou, China.
authors.forename: Xin
authors.initials: X
authors.lastname: Chen
authors.affiliation: Department of Clinical Laboratory, Sun Yat-sen Memorial Hospital, Sun Yat-Sen University, Guangzhou, China.
authors.forename: Hai-Yan
authors.initials: HY
authors.lastname: Yan
authors.affiliation: Laboratory of Rehabilitation, Guangdong Provincial Hospital, Guangzhou, China.
authors.forename: Bin
authors.initials: B
authors.lastname: Zeng
authors.affiliation: Laboratory of Rehabilitation, Guangdong Provincial Hospital, Guangzhou, China.
authors.forename: Ming-Sheng
authors.initials: MS
authors.lastname: Zhang
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D003430:Cross-Sectional Studies; D005080:Exercise Test; D017079:Exercise Tolerance / Q000502:physiology*; D005260:Female; D005541:Forced Expiratory Volume; D006801:Humans; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D029424:Pulmonary Disease, Chronic Obstructive / Q000503:physiopathology* / Q000523:psychology; D011788:Quality of Life / Q000523:psychology; D012893:Sleep Wake Disorders / Q000503:physiopathology* / Q000517:prevention & control / Q000523:psychology; D013147:Spirometry; D011795:Surveys and Questionnaires
keywords: chronic obstructive pulmonary disease; exercise capacity; sleep; sleep quality