title: The effects of nasal continuous positive airway pressure on platelet activation in obstructive sleep apnea syndrome.
abstract: OBJECTIVE
  A case-controlled study to assess the effects of nasal continuous positive airway pressure (CPAP) on platelet activation in patients with obstructive sleep apnea (OSAS) syndrome.
  
  
  METHODS
  We recruited 65 patients with suspected OSAS for this study. Blood samples were taken with the patient in the supine position in the morning immediately after polysomnography, and 1 night and 3 months after the start of nasal CPAP therapy to measure an index of platelet activation (IPA+), which reflected both the quantity and quality of platelet activation. Significant OSAS was defined as an apnea-hypopnea index (AHI) of > or = 10 events per hour.
  
  
  RESULTS
  There were 42 patients with significant OSAS and 23 control subjects with AHI < 10 events per hour. The mean (+/- SD) age for the OSAS patients was 48 +/- 9 years, the mean body mass index was 30.7 +/- 4.8, the mean AHI was 47 +/- 25 events per hour, the mean arousal index (AI) was 37 +/- 23 events per hour, and the mean minimum arterial oxygen saturation was 74 +/- 11%. Following multiple linear regression analyses of the clinical and polysomnography parameters, AI was the independent factor that correlated best with the baseline IPA+ (beta-coefficient, 0.386; p = 0.006). Following nasal CPAP treatment with a mean objective CPAP compliance of 3.9 +/- 1.9 h per night, there was a significant decrease in IPA+ from 15.1 +/- 12.2 U (at baseline) to 12.2 +/- 5.2 U (p < 0.001) and 9.8 +/- 4.3 U (p = 0.005), respectively, after 1 night and 3 months, whereas no significant change was noted among the control subjects. Using univariate analysis of variance to compare the changes in IPA+ between the two groups at 3 months with adjustment for the baseline value, nasal CPAP reduced IPA+ by 5.63 (SE, 1.85), whereas IPA+ increased in control subjects by 1.33 (SE, 1.27) [least-squared mean difference between groups, 3.34; 95% confidence interval, 0.42 to 6.26; p = 0.026].
  
  
  CONCLUSIONS
  OSAS, through repeated episodes of arousals, may lead to platelet activation, which can be reduced by nasal CPAP therapy.
authors.affiliation: Department of Medicine & Therapeutics, Chinese University of Hong Kong, Prince of Wales Hospital, Shatin, New Territories, Hong Kong. dschui@cuhk.edu.hk
authors.forename: David S
authors.initials: DS
authors.lastname: Hui
authors.forename: Fanny W
authors.initials: FW
authors.lastname: Ko
authors.forename: Joan P
authors.initials: JP
authors.lastname: Fok
authors.forename: Michael C
authors.initials: MC
authors.lastname: Chan
authors.forename: Thomas S
authors.initials: TS
authors.lastname: Li
authors.forename: Brian
authors.initials: B
authors.lastname: Tomlinson
authors.forename: Gregory
authors.initials: G
authors.lastname: Cheng
mesh_terms: D016022:Case-Control Studies; D045422:Continuous Positive Airway Pressure; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D015539:Platelet Activation; D020181:Sleep Apnea, Obstructive / Q000097:blood* / Q000628:therapy*