title: Obstructive sleep apnea and risk of cardiovascular events and all-cause mortality: a decade-long historical cohort study.
abstract: BACKGROUND
  Obstructive sleep apnea (OSA) has been reported to be a risk factor for cardiovascular (CV) disease. Although the apnea-hypopnea index (AHI) is the most commonly used measure of OSA, other less well studied OSA-related variables may be more pathophysiologically relevant and offer better prediction. The objective of this study was to evaluate the relationship between OSA-related variables and risk of CV events.
  
  
  RESULTS
  A historical cohort study was conducted using clinical database and health administrative data. Adults referred for suspected OSA who underwent diagnostic polysomnography at the sleep laboratory at St Michael's Hospital (Toronto, Canada) between 1994 and 2010 were followed through provincial health administrative data (Ontario, Canada) until May 2011 to examine the occurrence of a composite outcome (myocardial infarction, stroke, congestive heart failure, revascularization procedures, or death from any cause). Cox regression models were used to investigate the association between baseline OSA-related variables and composite outcome controlling for traditional risk factors. The results were expressed as hazard ratios (HRs) and 95% CIs; for continuous variables, HRs compare the 75th and 25th percentiles. Over a median follow-up of 68 months, 1,172 (11.5%) of 10,149 participants experienced our composite outcome. In a fully adjusted model, other than AHI OSA-related variables were significant independent predictors: time spent with oxygen saturation <90% (9 minutes versus 0; HR = 1.50, 95% CI 1.25-1.79), sleep time (4.9 versus 6.4 hours; HR = 1.20, 95% CI 1.12-1.27), awakenings (35 versus 18; HR = 1.06, 95% CI 1.02-1.10), periodic leg movements (13 versus 0/hour; HR = 1.05, 95% CI 1.03-1.07), heart rate (70 versus 56 beats per minute [bpm]; HR = 1.28, 95% CI 1.19-1.37), and daytime sleepiness (HR = 1.13, 95% CI 1.01-1.28).The main study limitation was lack of information about continuous positive airway pressure (CPAP) adherence.
  
  
  CONCLUSIONS
  OSA-related factors other than AHI were shown as important predictors of composite CV outcome and should be considered in future studies and clinical practice.
authors: Institute of Health Policy, Management and Evaluation, Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada.
authors: Tetyana
authors: T
authors: Kendzerska
authors: Institute of Health Policy, Management and Evaluation, Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada ; Department of Medicine, Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada ; Institute for Clinical Evaluative Sciences, Toronto, Ontario, Canada ; Department of Medicine, Sunnybrook Health Sciences Centre, Toronto, Ontario, Canada.
authors: Andrea S
authors: AS
authors: Gershon
authors: Institute of Health Policy, Management and Evaluation, Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada ; Department of Medicine, Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada ; Institute for Clinical Evaluative Sciences, Toronto, Ontario, Canada ; Department of Medicine, Women's College Hospital, Toronto, Ontario, Canada.
authors: Gillian
authors: G
authors: Hawker
authors: Department of Medicine, Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada ; Sleep Laboratory, St. Michael's Hospital, Toronto, Ontario, Canada ; Department of Medicine, St. Michael's Hospital, Toronto, Ontario, Canada.
authors: Richard S
authors: RS
authors: Leung
authors: Institute of Health Policy, Management and Evaluation, Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada ; Department of Medicine, Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada ; Department of Medicine, University Health Network/Mt Sinai Hospital, Toronto, Ontario, Canada.
authors: George
authors: G
authors: Tomlinson
mesh_terms: D000328:Adult; D002318:Cardiovascular Diseases / Q000175:diagnosis / Q000401:mortality*; D016009:Chi-Square Distribution; D018572:Disease-Free Survival; D005260:Female; D006801:Humans; D053208:Kaplan-Meier Estimate; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D049451:Nomograms; D009864:Ontario / Q000453:epidemiology; D017286:Polysomnography; D011237:Predictive Value of Tests; D011379:Prognosis; D016016:Proportional Hazards Models; D018570:Risk Assessment; D012307:Risk Factors; D020181:Sleep Apnea, Obstructive / Q000175:diagnosis / Q000401:mortality*; D013997:Time Factors