Article Text

Continuous positive airway pressure was beneficial in mild sleep apnoea-hypopnoea syndrome

Statistics from

Request Permissions

If you wish to reuse any or all of this article please use the link below which will take you to the Copyright Clearance Center’s RightsLink service. You will be able to get a quick price and instant permission to reuse the content in many different ways.

Engleman HM, Kingshott RN, Wraith PK, et al. Randomized placebo-controlled crossover trial of continuous positive airway pressure for mild sleep apnea/hypopnea syndrome. Am J Respir Crit Care Med. 1999 Feb;159: 461-7.


In patients with the sleep apnoea-hy- popnoea syndrome (SAHS), does con- tinuous positive airway pressure (CPAP) therapy improve symptoms, cognitive performance, and psychological well-being?


Randomised (unclear allocation concealment), unblinded, placebo-controlled, crossover trial with 4-week follow-up.


A sleep clinic in Edinburgh, Scotland.


37 patients with 2 symptoms of SAHS, including substantial sleepiness (Epworth sleepiness score 8 or admitted sleepiness while driving), and apnoea and hypopnoea index (AHI) of 5.0 to 14.9 per hour slept. Exclusion criteria included shift work, coexisting sleep disorders, or neurological or lung disease. 34 patients (92%) (mean age 44 y, 62% men) were included in the analysis.


Patients were initially allocated to CPAP therapy or placebo (2 tablets/d) for 4 weeks and a subsequent 4 weeks of crossover treatment with no washout period. 1 day of training was given on the use of Sullivan III CPAP units and heated CPAP humidifiers (ResMed Ltd., Abingdon, England, UK). An overnight CPAP titration study was done to determine optimal pressure for eliminating breathing irregularities and sleep arousals.

Main outcome measures

Sleepiness (maintenance of wakefulness test, Epworth sleepiness scale, and University of Wales Institute of Science and Technology mood adjective check list energetic arousal scale); symptoms (9-item questionnaire); cognitive performance (SteerClear, TrailMaking Tests A and B, Wechsler Adult Intelligence ScaleRevised scale performance IQ subtests: Digit Symbol Substitution and Block Design, and Paced Auditory Serial Addition Test [PASAT]); psychological well-being (Hospital Anxiety and Depression Scale); and health and functional status (Nottingham Health Profile Part 2 and Short Form-36).

Main results

CPAP therapy led to an improvement in symptoms, depression, and some measures of sleepiness, cognition, and health status (Table).


In patients with mild sleep apnoea-hypopnoea syndrome, continuous positive airway pressure therapy improved symptoms and some measures of cognition and psychological well-being.

Sources of funding: Glaxo (placebo tablets) and ResMed (CPAP Compliance metres).

For correspondence: Dr. H.M. Engleman, Scottish National Sleep Centre, Royal Infirmary of Edinburgh, Lauriston Place, Edinburgh EH3 9YW, Scotland, UK. FAX 44-131-536-2362.

Continuous positive airway pressure (CPAP) vs placebo for mild sleep apnoea-hypopnoea syndrome*

Outcomes at 4 wk Mean scores Effect size P value

CPAP Placebo

Symptom score (9 items) 11 16 0.63 0.003

Sleepiness (Epworth score) 8 11 0.75 0.008

Cognitive performance (Digit symbol) 59 57 0.50 0.004

Cognitive performance (PASAT-2) 40 36 0.36 0.02

Depression (HADS) 4.0 5.7 0.41 0.003

Health transition (SF-36) 2.6 3.0 0.50 0.03

Role-physical (SF-36) 81 64 0.55 0.03

Bodily pain (SF-36) 75 68 0.44 0.02

Social function (SF-36) 84 73 0.44 0.01

Vitality (SF-36) 58 46 0.67 0.001

*HADS = Hospital Anxiety and Depression Scale; PASAT = Paced Auditory Serial Addition Test; SF-36 = Short Form-36


The literature on SAHS has been criticised for lack of adequate controls. The study by Engleman and colleagues showed more benefit with CPAP therapy in mild SAHS than with oral placebo. In more severe SAHS, CPAP therapy has been shown to be much more effective than a machine set at sub-therapeutic pressure (1) or conservative advice, including weight loss (2). These studies remove any lingering doubts about the effectiveness of CPAP on sleepiness and symptoms resulting from SAHS.

Engleman and colleagues show that mild SAHS can be associated with substantial symptoms that can be improved by CPAP therapy, but many patients may not consider the benefit worth the inconvenience. Only 14 of 34 patients preferred CPAP. Symptoms of SAHS and the benefit of CPAP therapy correlate poorly with conventional measures of severity, such as the AHI.

A practical approach to management of sleepy patients is to investigate for SAHS when sleepiness has no other obvious cause. A trial of effectiveness and acceptability of CPAP therapy should be considered for suitably motivated patients with sufficient symptoms, even if the AHI is low. Such treatments as mandibular advancement splints are another option in mild SAHS (3).

Treatment should be based on symptoms and sleep study findings, not on AHI alone or possible long-term vascular consequences for which no adequate studies exist.

P. John Rees, MD

Guy's Hospital

London, England, UK


1. Jenkinson C, Davies RJ, Mullins R, Stradling JR. Lancet. 1999;353:2100-5.

2. Ballester E, Badia JR, Hernandez L, et al. Am J Respir Crit Care Med. 1999;159:495-501.

3. Clark GT, Blumenfeld I, Yoffe N, Peled E, Lavie P. Chest. 1996;109:1477-83.