title: Nocturnal Hypoxemia Is Associated with White Matter Hyperintensities in Patients with a Minor Stroke or Transient Ischemic Attack.
abstract: OBJECTIVE
  Obstructive sleep apnea (OSA) is a risk factor for stroke, which is modulated by accompanying nocturnal hypoxemia. White matter hyperintensities (WMH) share many of the same risk factors as stroke. The purpose of this study was to investigate whether OSA and nocturnal hypoxemia are associated with white matter disease in patients with minor stroke and transient ischemic attack.
  
  
  METHODS
  Patients with minor stroke or TIA were recruited. Level 3 diagnostic sleep testing was used to diagnose OSA and quantify nocturnal hypoxemia. Significant OSA was defined as respiratory disturbance index ≥ 15, and nocturnal hypoxemia was defined as oxyhemoglobin saturation < 90% for ≥ 12% of total monitoring time. WMH were assessed and quantified on FLAIR MRI. The volume of WMH was compared between those with and without significant OSA and between those with and without nocturnal hypoxemia.
  
  
  RESULTS
  One hundred nine patients were included. Thirty-four (31%) had OSA and 37 (34%) had nocturnal hypoxemia. Total WMH volume was significantly greater in the OSA than in the non-OSA groups (p = 0.04). WMH volume was also significantly higher in the hypoxic than the non-hypoxic groups (p = 0.001). Mutivariable analysis with adjustment for age, hypertension, and diabetes showed that nocturnal hypoxemia was independently associated with WMH volume (p = 0.03) but OSA was not (p = 0.29).
  
  
  CONCLUSIONS
  We conclude that nocturnal hypoxemia, predominantly related to OSA, is independently associated with WMH in patients who present with minor ischemic stroke and TIA and may contribute to its pathogenesis.
authors.affiliation: Clinical Neurosciences, Foothills Medical Centre, University of Calgary, Calgary, Alberta, Canada.
authors.forename: Shiel K
authors.initials: SK
authors.lastname: Patel
authors.affiliation: Medicine, Foothills Medical Centre, University of Calgary, Calgary, Alberta, Canada.|Hotchkiss Brain Institute, Foothills Medical Centre, University of Calgary, Calgary, Alberta, Canada.|Sleep Centre, Foothills Medical Centre, University of Calgary, Calgary, Alberta, Canada.
authors.forename: Patrick J
authors.initials: PJ
authors.lastname: Hanly
authors.affiliation: Clinical Neurosciences, Foothills Medical Centre, University of Calgary, Calgary, Alberta, Canada.|Radiology, Foothills Medical Centre, University of Calgary, Calgary, Alberta, Canada.|Community Health Sciences, Foothills Medical Centre, University of Calgary, Calgary, Alberta, Canada.|Hotchkiss Brain Institute, Foothills Medical Centre, University of Calgary, Calgary, Alberta, Canada.|Seaman Family MR Centre, Foothills Medical Centre, University of Calgary, Calgary, Alberta, Canada.
authors.forename: Eric E
authors.initials: EE
authors.lastname: Smith
authors.affiliation: Clinical Neurosciences, Foothills Medical Centre, University of Calgary, Calgary, Alberta, Canada.
authors.forename: Wesley
authors.initials: W
authors.lastname: Chan
authors.affiliation: Clinical Neurosciences, Foothills Medical Centre, University of Calgary, Calgary, Alberta, Canada.|Radiology, Foothills Medical Centre, University of Calgary, Calgary, Alberta, Canada.|Community Health Sciences, Foothills Medical Centre, University of Calgary, Calgary, Alberta, Canada.|Hotchkiss Brain Institute, Foothills Medical Centre, University of Calgary, Calgary, Alberta, Canada.|Seaman Family MR Centre, Foothills Medical Centre, University of Calgary, Calgary, Alberta, Canada.
authors.forename: Shelagh B
authors.initials: SB
authors.lastname: Coutts
mesh_terms: D005260:Female; D006801:Humans; D000860:Hypoxia / Q000150:complications* / Q000503:physiopathology*; D002546:Ischemic Attack, Transient / Q000145:classification*; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D012307:Risk Factors; D020521:Stroke / Q000150:complications*; D066127:White Matter / Q000503:physiopathology*
keywords: MRI; TIA; hypoxia; obstructive sleep apnea; stroke; white matter disease