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Patients with the sleep apnoea/hypopnoea syndrome (SAHS) have impaired daytime function with demonstrable sleepiness and impaired cognition. The hypothesis that brief arousals from sleep cause these daytime impairments was tested. One hundred and fifty patients with sleep disordered breathing were studied prospectively, comparing overnight polysomnography with daytime measures of objective sleepiness, psychological well-being and cognitive performance. Significant, but weak (r2<0.1), relationships were seen between several nocturnal measures (apnoea/hypopnoea index, arousals and desaturation variables) and daytime measures of quality of life, well-being, subjective sleepiness, symptoms and cognitive performance. The only significant relationship between nocturnal variables and objective sleepiness was a very weak correlation (r2<0.05) between the lowest oxygen saturation and mean maintenance of wakefulness test (MWT) result. The MWT was better correlated with daytime function than the multiple sleep latency test. This study shows a lack of strong relationships between conventional nocturnal measures and daytime function in patients with sleep disordered breathing.

Patients with the sleep apnea/hypopnea syndrome suffer from impaired daytime function. This has been attributed to both sleep fragmentation and hypoxemia. To help understand which is casual, we studied the effects of sleep fragmentation alone on daytime function. Sixteen normal subjects were studied on two pairs of two nights. The first night of each pair was for acclimatization, and on the second the subject either slept undisturbed or had sleep fragmented with sound pulses every 2 min. Sound volume and duration was titrated to cause a return to theta or alpha rhythm on the EEG for at least 3 s. Study nights were followed by daytime testing of psychometric function and mood and by a multiple sleep latency test (MSLT) and a maintenance of wakefulness test (MWT). Total sleep time did not differ between study nights (400 +/- 20 SD min undisturbed, 396 +/- 24 min fragmented; p = 0.6). Fragmentation decreased sleep latency on both the MSLT (11 +/- 3, 7 +/- 2 min; p = 0.001) and the MWT (34 +/- 8, 24 +/- 10 min; p<0.001). Energetic arousal (22 +/- 4, 19 +/- 4; p = 0.005) and hedonic tone (29 +/- 4, 27 +/- 4; p = 0.05) decreased after fragmentation. Fragmentation impaired daytime function adjudged by the Trailmaking B (p = 0.05) and PASAT 4-s tests (p<0.03). One night of sleep fragmentation makes normal subjects sleepier during the day, impairs their subjective assessment of mood, and decreases mental flexibility and sustained attention.

Continuous positive airway pressure (CPAP) is the treatment of choice for the sleep apnoea/hypopnoea syndrome (SAHS); it is usually given with the aim of improving daytime cognitive function, mood, and sleepiness. However, its efficacy has not been validated by controlled trials. We have carried out a randomised, placebo-controlled, crossover study of objective daytime sleepiness, symptoms, cognitive function, and mood in a consecutive series of 32 SAHS patients with a median apnoea plus hypopnoea frequency of 28 (range 7-129) per hour slept. Patients were treated with 4 weeks each of CPAP and an oral placebo, which they were told might improve upper airway muscle function during sleep. Assessments on the last day of each treatment included a multiple sleep latency test and tests of symptom scores, mood profiles, and cognitive performance. The patients had significantly less daytime sleepiness on CPAP than during the placebo period (mean sleep latency 7.2 [SE 0.7] vs 6.1 [0.7] min, p = 0.03). There were also improvements with CPAP in symptom ratings (2.1 [0.2] vs 4.3 [0.3], p < 0.001), mood (p < 0.05 for several measures), and cognitive performance, which showed improved vigilance (obstacles hit in Steer Clear "driving" test 76 [5] vs 81 [6], p < 0.01), mental flexibility (trail-making B time 66 [5] vs 75 [5] s, p < 0.05), and attention (p < 0.05). Objectively monitored CPAP use averaged only 3.4 (0.4) hours per night, but this study provides evidence of improved cognitive performance even at this low level of CPAP compliance.

Background: Patients with the sleep apnoea/hypopnoea syndrome often receive continuous positive airway pressure to improve their symptoms and daytime performance, yet objective evidence of the effect of this treatment on cognitive performance is lacking., Methods: A prospective parallel group study was performed comparing the change in objective daytime sleepiness as assessed by multiple sleep latency, cognitive function, and mood in 21 patients (mean (SE) number of apnoeas and hypopnoeas/hour 57 (6)) who received continuous positive airway pressure for three months and 16 patients (49(6) apnoeas and hypopnoeas/hour) who received conservative treatment for a similar period., Results: Both groups showed significant within group changes in cognitive function between baseline and three months, but when comparisons were made between groups the only significant difference was a greater improvement in multiple sleep latency with continuous positive airway pressure. However, the improvement in sleep latency with continuous positive airway pressure was relatively small (3.5 (0.5) to 5.6 (0.7) min). The group treated with continuous positive airway pressure was divided into those who complied well with treatment (> 4.5 hours/night) and those who did not. Those who complied well (n = 14) showed significant improvement in mean sleep latency and also in depression score compared with the controls but no greater improvement in cognitive function., Conclusion: This study confirms significant improvements in objective sleepiness and mood with continuous positive airway pressure, but shows no evidence of major improvements in cognitive function.

The effect of theophylline on sleep quality and cognitive performance in patients with obstructive lung disease has been the subject of controversy. To examine the direct effects of theophylline on sleep quality and cognitive performance, without confounding effects from bronchodilatation, we have undertaken a study of the drug in healthy subjects. A double-blind, placebo-controlled crossover protocol was used to study the effect of oral sustained-release theophylline (Theodur) on subjective sleep quality, objective sleep quality, and cognitive performance. Overnight sleep studies were carried out on Nights 13 and 14 of each 2-wk study limb, and cognitive performance tests administered on Days 1 and 13 of each limb. A total of 18 subjects satisfactorily completed the study (8 males, median age 37, range 24 to 67 yr). Theophylline levels were median 10.2, range 2.3 to 13.3 micrograms/ml on Day 1 and 14.7, range 9.6 to 17.5 micrograms/ml on Day 13. No significant difference was observed between theophylline and placebo on subjective or objective sleep quality or on acute or medium-term cognitive performance. We conclude that theophylline does not affect sleep quality or cognitive performance in normal adults.