title: Overlap syndrome between chronic obstructive pulmonary disease and obstructive sleep apnoea in a Southeast Asian teaching hospital.
abstract: BACKGROUND
  Overlap syndrome between obstructive sleep apnoea (OSA) and chronic obstructive pulmonary disease (COPD) is important but under-recognised. We aimed to determine the prevalence of overlap syndrome and the predictors of OSA in patients with COPD.
  
  
  METHODS
  Patients aged ≥ 40 years were recruited from a dedicated COPD clinic and underwent overnight polysomnography. A diagnosis of OSA was made when apnoea-hypopnoea index (AHI) was ≥ 5.
  
  
  RESULTS
  In all, 22 patients (aged 71 ± 9 years), predominantly men, were recruited. Mean values recorded were: predicted forced expiratory volume in the first second percentage 55 ± 15; body mass index 23.7 ± 6.5 kg/m2; Epworth Sleepiness Scale score 5.6 ± 5.8; and AHI 15.8 ± 18.6. Among the 14 patients with OSA (prevalence of overlap syndrome at 63.6%), the mean number of hospital visits for COPD exacerbations in the preceding one year was 0.5 ± 0.7. Patients with overlap syndrome had worse modified Medical Research Council dyspnoea scale scores and a lower percentage of rapid eye movement (REM) sleep than patients without. There were no other statistical differences in lung function or sleep study indices between the two patient groups.
  
  
  CONCLUSIONS
  The majority of our patients had overlap syndrome and minimal exacerbations, and were not obese or sleepy. Significant differences between patients with and without overlap syndrome were seen in two aspects - the former was more dyspnoeic and had less REM sleep. Our findings suggest that standard clinical predictors cannot be used for patients with overlap syndrome, and therefore, a high index of suspicion is needed.
authors.affiliation: Department of Respiratory and Critical Care Medicine, Changi General Hospital, 2 Simei Street 3, Singapore 529889. sridhar_venkateswaran@cgh.com.sg.
authors.forename: Sridhar
authors.initials: S
authors.lastname: Venkateswaran
authors.forename: Augustine
authors.initials: A
authors.lastname: Tee
mesh_terms: D000328:Adult; D000368:Aged; D015992:Body Mass Index; D015331:Cohort Studies; D015897:Comorbidity; D005260:Female; D005541:Forced Expiratory Volume; D006784:Hospitals, Teaching; D006801:Humans; D008297:Male; D008875:Middle Aged; D017286:Polysomnography; D015995:Prevalence; D029424:Pulmonary Disease, Chronic Obstructive / Q000150:complications* / Q000175:diagnosis*; D012129:Respiratory Function Tests; D012846:Singapore; D020181:Sleep Apnea, Obstructive / Q000150:complications* / Q000175:diagnosis*; D012895:Sleep, REM