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Continuous positive airway pressure reduces daytime sleepiness in mild to moderate obstructive sleep apnoea: a meta-analysis
  1. N S Marshall1,
  2. M Barnes2,
  3. N Travier1,3,
  4. A J Campbell4,
  5. R J Pierce2,
  6. R D McEvoy5,
  7. A M Neill4,
  8. P H Gander1
  1. 1Sleep/Wake Research Centre, Massey University, New Zealand
  2. 2Institute for Sleep and Breathing, Austin Health, Heidelberg, Victoria, Australia
  3. 3Centre for Public Health Research, Massey University, New Zealand
  4. 4WellSleep, Department of Medicine, Wellington School of Medicine, University of Otago, New Zealand
  5. 5Adelaide Institute for Sleep Health, Repatriation General Hospital, Daw Park, South Australia, Australia
  1. Correspondence to:
    Dr N S Marshall
    Sleep and Circadian Research Group, Woolcock Institute of Medical Research, P O Box M77, Missenden Road, NSW 2050, Australia; nmarshall{at}


Background: Obstructive sleep apnoea syndrome (OSAS) affects an estimated 2–4% of the middle aged population. Meta-analyses of randomised controlled trials have shown that the severe presentation of the syndrome (apnoea hypopnoea index (AHI) >30/hour) is effectively treated with continuous positive airway pressure (CPAP). Until recently there have been insufficient data to determine whether CPAP improves sleepiness in the larger subgroup with mild to moderate OSAS (AHI 5–30/hour).

Methods: A systematic search of Medline and a hand search identified seven randomised controlled trials where CPAP was compared with either a placebo or with conservative management in the treatment of mild to moderate OSAS (AHI 5–30/hour). All trials used the Epworth Sleepiness Scale (ESS), four used the Multiple Sleep Latency Test (MSLT), and three used the Maintenance of Wakefulness Test (MWT) to measure sleepiness.

Results: Meta-analyses indicated that CPAP significantly reduced subjective daytime sleepiness (ESS) by 1.2 points (95% CI 0.5 to 1.9, p = 0.001), improved objective daytime wakefulness (MWT) by 2.1 minutes (95% CI 0.5 to 3.7, p = 0.011), but did not affect objective daytime sleepiness (MSLT, mean benefit −0.2 minutes, 95% CI −1.0 to 0.6, p = 0.6). The two significant effects were small (effect size <0.30).

Conclusions: CPAP elicits small improvements in subjective sleepiness and objective wakefulness in people with mild to moderate OSAS. However, the effects on sleepiness are of limited clinical significance.

  • AHI, apnoea hypnoea index
  • BMI, body mass index
  • CPAP, continuous positive airway pressure
  • ESS, Epworth Sleepiness Scale
  • MSLT, Multiple Sleep Latency Test
  • MWT, Maintenance of Wakefulness Test
  • OSAS, obstructive sleep apnoea syndrome
  • continuous positive airway pressure
  • obstructive sleep apnoea
  • meta-analysis

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  • Published Online First 7 February 2006

  • This project was supported by the funding of a PhD stipend to NSM by Massey University and the Sleep Wake Research Centre.

  • Competing interests: none.