Evaluation of sham-CPAP as a placebo in CPAP intervention studies

Functional recovery after ischemic stroke: Impact of different sleep health parameters

Sleep disturbances after ischaemic stroke include alterations of sleep architecture, obstructive sleep apnea, restless legs syndrome, daytime sleepiness and insomnia. Our aim was to explore their impacts on functional outcomes at month 3 after stroke, and to assess the benefit of continuous positive airway pressure in patients with severe obstructive sleep apnea. Ninety patients with supra-tentorial ischaemic stroke underwent clinical screening for sleep disorders and polysomnography at day 15 ± 4 after stroke in a multisite study. Patients with severe obstructive apnea (apnea-hypopnea index ≥ 30 per hr) were randomized into two groups: continuous positive airway pressure-treated and sham (1:1 ratio). Functional independence was assessed with the Barthel Index at month 3 after stroke in function of apnea-hypopnea index severity and treatment group. Secondary objectives were disability (modified Rankin score) and National Institute of Health Stroke Scale according to apnea-hypopnea index. Sixty-one patients (71.8 years, 42.6% men) completed the study: 51 (83.6%) had obstructive apnea (21.3% severe apnea), 10 (16.7%) daytime sleepiness, 13 (24.1%) insomnia, 3 (5.7%) depression, and 20 (34.5%) restless legs syndrome. Barthel Index, modified Rankin score and Stroke Scale were similar at baseline and 3 months post-stroke in the different obstructive sleep apnea groups. Changes at 3 months in those three scores were similar in continuous positive airway pressure versus sham-continuous positive airway pressure patients. In patients with worse clinical outcomes at month 3, mean nocturnal oxygen saturation was lower whereas there was no association with apnea-hypopnea index. Poorer outcomes at 3 months were also associated with insomnia, restless legs syndrome, depressive symptoms, and decreased total sleep time and rapid eye movement sleep.

The placebo effect in pharmacological treatment of obstructive sleep apnea, a systematic review and meta-analysis

OBJECTIVE

New drug treatments are under development in obstructive sleep apnea (OSA). The placebo effect is well recognized in various conditions, but its relevance in OSA is debated. In the current study we determined the influence of a placebo effect in studies of drug therapy in OSA.

METHODS

A systematic review and meta-analysis (PROSPERO CRD42021229410) with searches in MEDLINE, Scopus, Web of Science and Cochrane CENTRAL from inception to 2021-01-19. Inclusion criteria were (i) RCTs of adults with OSA, (ii) drug intervention with placebo baseline and follow-up sleep study (iii) outcomes: apnea hypopnea index (AHI), mean oxygen saturation (mSaO2), oxygen desaturation index (ODI) and/or Epworth Sleepiness Scale (ESS). Risk-of-bias was assessed with Cochrane RoB 2.

RESULTS

7436 articles were identified and 29 studies included (n = 413). Studies were generally small (median n = 14), with 78% men, baseline AHI range 9-74 events/h and treatment duration range 1-120 days. Meta-analyses were conducted for main outcomes. Mean change of the primary outcome, AHI, was -0.84 (95% CI -2.98 to 1.30); mSaO2 and ODI estimations were also non-significant. ESS showed a trend towards a reduction of -1 unit. Subgroup analysis did not show significant differences. Risk-of-bias assessment indicated mostly low risk but studies were small with wide confidence intervals.

CONCLUSIONS

In this meta-analysis we did not identify systematic placebo effects on the AHI, ODI or mSaO2 while ESS score showed a trend for a small reduction. These results have an impact on the design and interpretation of drug trials in OSA.

A trial of positive airway pressure for the treatment of sleep apnea in pregnancy

BACKGROUND

The pathophysiology of obstructive sleep apnea in pregnancy remains poorly understood and studies examining the effect of treatment with positive airway pressure on pregnancy have been limited.

OBJECTIVE

This study aimed to perform a randomized controlled trial of positive airway pressure treatment for obstructive sleep apnea in pregnancy.

STUDY DESIGN

Participants with a body mass index ≥30 kg/m² underwent polysomnography at 14 to 20 weeks' gestation (visit 1) and those with obstructive sleep apnea (apnea-hypopnea index ≥5 but <50) were enrolled. In phase 1, participants were randomized to autotitrating positive airway pressure vs sham positive airway pressure; in phase 2, the sham arm was replaced with a sleep hygiene control. Participants returned at 28 to 31 weeks' gestation (visit 2). The mean arterial blood pressure, uterine artery Doppler pulsatility index, endoglin, soluble FMS-like tyrosine kinase 1 levels, and placental growth factor levels were measured, as well as fasting glucose and insulin to calculate insulin resistance (homeostatic model assessment for insulin resistance). The primary outcome was a composite of the uterine artery Doppler pulsatility index, soluble FMS-like tyrosine kinase 1 to placental growth factor ratio, and the homeostatic model assessment for insulin resistance. For secondary analyses, each outcome variable was analyzed independently. Adherence to treatment was examined.

RESULTS

A total of 241 participants completed visit 1, and 89 (37%) had an apnea-hypopnea index between 5 and 50. Of the those, 51 participants were randomized in phase 1 and 38 in phase 2. There was no significant difference in our primary outcome by treatment group. In secondary analyses, the uterine artery Doppler pulsatility index was lower in participants on autotitrating positive airway pressure when compared with sleep hygiene controls. Otherwise, there were no differences in the mean arterial blood pressure, angiogenic markers, or metabolic markers in phase 1, phase 2, or across the entire study. The overall adherence to autotitrating positive airway pressure therapy was low, but the mean use was greater in phase 2 (0.3±0.6 hours/night vs 1.3±2.3 hours/night; P=.10). For those on active therapy, fasting glucose values decreased as adherence increased.

CONCLUSION

This randomized controlled trial of autotitrating positive airway pressure in pregnancy did not find any differences in a composite primary cardiometabolic risk profile between the treatment groups. Higher autotitrating positive airway pressure adherence was associated with lower fasting glucose levels. The use of a sham positive airway pressure control arm in phase1 may have negatively impacted adherence to active treatment.

Placebo response in objective and subjective measures of hypersomnia in randomized clinical trials on obstructive sleep apnea. A systematic review and meta-analysis

Sleepiness is one of the outcomes most used in randomized clinical trials (RCT) on the effect of treatments for obstructive sleep apnea (OSA). Furthermore, it is known that there is a placebo effect, especially in subjective measures. Therefore, given that sleepiness is a subjective measure, the objective of this systematic review with meta-analysis and three-level meta-regression was to assess the response to different placebos (pills and sham-CPAP) used in RCTs in OSA, both on subjective (Epworth Sleepiness Scale [ESS]) and objective (Multiple Sleep Latency Test [MSLT], Maintenance Wake Test [MWT], the Osler test and the Psychomotor Vigilance Task [PVT]). We observed a statistically significant placebo effect in both subjective and objective measures of hypersomnia, and in both sham-CPAP and pills. This placebo effect was greater, even clinically significant, in subjective measures (ESS: -2.84 points) and in those RCTs that used pills as a placebo. In the meta-regression, only a higher baseline value of the ESS and Osler test was related to the placebo effect.

Continuous positive airway pressure in cluster headache: A randomized, placebo-controlled, triple-blind, crossover study

BACKGROUND

Oxygen inhalation aborts cluster headache attacks, and case reports show the effect of continuous positive airway pressure. The aim of this study was to investigate the prophylactic effect of continuous positive airway pressure in chronic cluster headache.

METHODS

This was a randomized placebo-controlled triple-blind crossover study using active and sham continuous positive airway pressure treatment for chronic cluster headache. Patients entered a one month's baseline period before randomly being assigned to two months' active continuous positive airway pressure treatment followed by a four weeks' washout period and two months' sham continuous positive airway pressure or vice versa. Primary outcome measure was number of cluster headache attacks/week.

RESULTS

Of the 30 included participants (12 males, median age 49.5 years, min-max 20-66 years), 25 completed both treatment/sham cycles (two discontinued, three lost to follow-up). The median number of cluster headache attacks per week was reduced from 8.25 (0.75-89.75) attacks to 6.25 (0-56.00) attacks for active continuous positive airway pressure and to 7.50 (0.50-43.75) attacks for sham continuous positive airway pressure, but there was no difference in active versus sham (p = 0.904). One patient had a serious adverse event during active treatment, none occurred during sham treatment.

CONCLUSIONS

Continuous positive airway pressure treatment did not reduce the number of cluster headache attacks compared to sham treatment in chronic cluster headache patients.

TRIAL REGISTRATION CLINICALTRIALS.GOV

NCT03397563.

Feasibility of remote neurocognitive assessment: pandemic adaptations for a clinical trial, the Cognition and Obstructive Sleep Apnea in Parkinson's Disease, Effect of Positive Airway Pressure Therapy (COPE-PAP) study

Background

The COVID-19 pandemic poses challenges for timely outcome assessment in randomized clinical trials (RCT). Our aim was to describe our remote neurocognitive testing (NCT) protocol administered by telephone in patients with Parkinson’s disease (PD) and obstructive sleep apnea (OSA).

Methods

We studied PD patients with OSA and Montreal Cognitive Assessment (MoCA) score ≤ 27 participating in a RCT assessing OSA treatment impact on cognition. Trial outcomes included change in MoCA and specific cognitive domains from baseline to 3 and 6 months. With COVID19 pandemic-related restrictions, 3-month visits were converted from in-person to telephone administration with materials mailed to participants for compatible tests and retrieved by courier the same day. In exploratory analyses, we compared baseline vs. 3-month results in the control arm, which were not expected to change significantly (test-re-test), using a paired t-test and assessed agreement with the intraclass correlation coefficient (ICC).

Results

Seven participants were approached and agreed to remote NCT at 3-month follow-up. Compared to the in-person NCT control arm group, they were younger (60.6 versus 70.6 years) and had a shorter disease course (3.9 versus 9.2 years). Remote NCT data were complete. The mean test-retest difference in MoCA was similar for in-person and remote NCT control-arm groups (between group difference − 0.69; 95%CI − 3.67, 2.29). Agreement was good for MOCA and varied for specific neurocognitive tests.

Conclusion

Telephone administration of the MoCA and a modified neurocognitive battery is feasible in patients with PD and OSA. Further validation will require a larger sample size.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13063-021-05879-1.

Changes in cortisol levels by continuous positive airway pressure in patients with obstructive sleep apnoea: Meta-analysis of 637 individuals

BACKGROUND

Obesity, obstructive sleep apnoea (OSA) and hypertension frequently coexist and are associated with elevated cortisol levels. Identification and treatment of such patients is important when investigating for suspected Cushing's syndrome and hypertension. Studies of the impact of continuous positive airway pressure (CPAP) on cortisol and blood pressure are limited by the small sample size and show conflicting findings. We conducted a meta-analysis to document changes in the levels of cortisol and blood pressure in response to CPAP treatment of OSA.

METHODS

Meta-analysis was conducted using RevMan (v5.3) and expressed in standardized mean difference (SMD) for catecholamines and mean difference for systolic (SBP) and diastolic blood pressure (DBP). The quality of the studies was evaluated using standard tools for assessing the risk of bias.

RESULTS

A total of 22 studies met our search criteria; they consisted of 16 prospective cohort studies (PCS) that recruited 385 participants and six randomized control trials (RCT) totalling 252 participants. The range of mean age was 41-62 years and BMI 27.2-35.1 kg/m² . CPAP treatment reduced plasma cortisol levels in PCS: SMD = -0.28 [95% confidence interval (95% CI) = -0.45 to -0.12], I²  = 0%, p = .79 and in RCT: SMD = -0.39 (95% CI = -0.75 to -0.03), I²  = 28.3%, p = .25. CPAP treatment reduced SBP by 5.4 mmHg (95% CI = 1.7-9.1) and DBP by 3.3 mmHg (95% CI = 1.0-5.7). Interstudy heterogeneity was low for all studies. Bias in most RCT arose from the lack of blinding of participants and personnel.

CONCLUSION

CPAP treatment in individuals with OSA reduces cortisol levels and blood pressure.

Chronic non-invasive ventilation for chronic obstructive pulmonary disease

BACKGROUND

Chronic non-invasive ventilation (NIV) is increasingly being used to treat people with COPD who have respiratory failure, but the evidence supporting this treatment has been conflicting.

OBJECTIVES

To assess the effects of chronic non-invasive ventilation at home via a facial mask in people with COPD, using a pooled analysis of IPD and meta-analysis.

SEARCH METHODS

We searched the Cochrane Airways Register of Trials, MEDLINE, Embase, PsycINFO, CINAHL, AMED, proceedings of respiratory conferences, clinical trial registries and bibliographies of relevant studies. We conducted the latest search on 21 December 2020.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) comparing chronic NIV for at least five hours per night for three consecutive weeks or more (in addition to standard care) versus standard care alone, in people with COPD. Studies investigating people initiated on NIV in a stable phase and studies investigating NIV commenced after a severe COPD exacerbation were eligible, but we reported and analysed them separately. The primary outcomes were arterial blood gases, health-related quality of life (HRQL), exercise capacity (stable COPD) and admission-free survival (post-exacerbation COPD). Secondary outcomes for both populations were: lung function, COPD exacerbations and admissions, and all-cause mortality. For stable COPD, we also reported respiratory muscle strength, dyspnoea and sleep efficiency.

DATA COLLECTION AND ANALYSIS

We used standard methodological procedures expected by Cochrane. After inclusion of a study, we requested the IPD. We analysed continuous and time-to-event data using linear- and cox-regression mixed-effect models with a random effect on study level. We analysed dichotomous IPD using generalised estimating equations. We adjusted all models for age and sex. We assessed changes in outcomes after three and 12 months.  We also conducted a meta-analysis on aggregated trial data.

MAIN RESULTS

We included 14 new RCTs in this review update, in addition to the seven previously included. Seventeen studies investigated chronic NIV in stable COPD and four studies investigated chronic NIV commenced after a severe COPD exacerbation. Three studies compared NIV to sham continuous positive airway pressure (2 to 4 cmH₂O). Seven studies used a nasal mask, one study used an oronasal mask and eight studies used both interfaces. Five studies did not report the interface. The majority of trials (20/21) were at high risk of performance bias due to an unblinded design. We considered 11 studies to have a low risk of selection bias and 13 to have a low risk of attrition bias. We collected and analysed the IPD from 13 stable COPD studies (n = 778, 68% of the participants included) and from three post-exacerbation studies (n = 364, 96% of the participants included). In the stable COPD group, NIV probably results in a minor benefit on the arterial partial pressure of oxygen (PaO₂) after three months (adjusted mean difference (AMD) 0.27 kPa, 95% CI 0.04 to 0.49; 9 studies, 271 participants; moderate-certainty evidence), but there was little to no benefit at 12 months (AMD 0.09 kPa, 95% CI -0.23 to 0.42; 3 studies, 171 participants; low-certainty evidence). The arterial partial pressure of carbon dioxide (PaCO₂) was reduced in participants allocated to NIV after three months (AMD -0.61 kPa, 95% CI -0.77 to -0.45; 11 studies, 475 participants; high-certainty evidence) and persisted up to 12 months (AMD -0.42 kPa, 95% CI -0.68 to -0.16; 4 studies, 232 participants; high-certainty evidence).  Exercise capacity was measured with the 6-minute walking distance (minimal clinical important difference: 26 m). There was no clinically relevant effect of NIV on exercise capacity (3 months: AMD 15.5 m, 95% CI -0.8 to 31.7; 8 studies, 330 participants; low-certainty evidence; 12 months: AMD 26.4 m, 95% CI -7.6 to 60.5; 3 studies, 134 participants; very low-certainty evidence). HRQL was measured with the Severe Respiratory Insufficiency and the St. Georges's Respiratory Questionnaire and may be improved by NIV, but only after three months (3 months: standardised mean difference (SMD) 0.39, 95% CI 0.15 to 0.62; 5 studies, 259 participants; very low-certainty evidence; 12 months: SMD 0.15, 95% CI -0.13 to 0.43; 4 studies, 200 participants; very low-certainty evidence). Lastly, the risk for all-cause mortality is likely reduced by NIV (adjusted hazard ratio (AHR) 0.75, 95% CI 0.58 to 0.97; 3 studies, 405 participants; moderate-certainty evidence). In the post-exacerbation COPD group, there was little to no benefit on the PaO₂ after three months, but there may be a slight decrease after 12 months (3 months: AMD -0.10 kPa, 95% CI -0.65 to 0.45; 3 studies, 234 participants; low-certainty evidence; 12 months: -0.27 kPa, 95% CI -0.86 to 0.32, 3 studies; 170 participants; low-certainty evidence). The PaCO₂ was reduced by NIV at both three months (AMD -0.40 kPa, 95% CI -0.70 to -0.09; 3 studies, 241 participants; moderate-certainty evidence) and 12 months (AMD -0.52 kPa, 95% CI -0.87 to -0.18; 3 studies, 175 participants; high-certainty evidence). NIV may have little to no benefit on HRQL (3 months: SMD 0.25, 95% CI -0.01 to 0.51; 2 studies, 219 participants; very low-certainty evidence; 12 months: SMD 0.25, 95% -0.06 to 0.55; 2 studies, 164 participants; very low-certainty evidence). Admission-free survival seems improved with NIV (AHR 0.71, 95% CI 0.54 to 0.94; 2 studies, 317 participants; low-certainty evidence), but the risk for all-cause mortality does not seem to improve (AHR 0.97, 95% CI 0.74 to 1.28; 2 studies, 317 participants; low-certainty evidence).

AUTHORS' CONCLUSIONS

Regardless of the timing of initiation, chronic NIV improves daytime hypercapnia. In addition, in stable COPD, survival seems to be improved and there might be a short term HRQL benefit. In people with persistent hypercapnia after a COPD exacerbation, chronic NIV might prolong admission-free survival without a beneficial effect on HRQL. In stable COPD, future RCTs comparing NIV to a control group receiving standard care might no longer be warranted, but research should focus on identifying participant characteristics that would define treatment success. Furthermore, the optimal timing for initiation of NIV after a severe COPD exacerbation is still unknown.

A randomized sham-controlled trial on the effect of continuous positive airway pressure treatment on gait control in severe obstructive sleep apnea patients

To determine the effect of continuous positive airway pressure (CPAP), the gold standard treatment for obstructive sleep apnea syndrome (OSAS), on gait control in severe OSAS patients. We conducted a randomized, double-blind, parallel-group, sham-controlled monocentric study in Grenoble Alpes University Hospital, France. Gait parameters were recorded under single and dual-task conditions using a visuo-verbal cognitive task (Stroop test), before and after the 8-week intervention period. Stride-time variability, a marker of gait control, was the primary study endpoint. Changes in the determinants of gait control were the main secondary outcomes. ClinicalTrials.gov Identifier: (NCT02345694). 24 patients [median (Q1; Q3)]: age: 59.5 (46.3; 66.8) years, 87.5% male, body mass index: 28.2 (24.7; 29.8) kg. m⁻², apnea–hypopnea index: 51.6 (35.0; 61.4) events/h were randomized to be treated by effective CPAP (n = 12) or by sham-CPAP (n = 12). A complete case analysis was performed, using a mixed linear regression model. CPAP elicited no significant improvement in stride-time variability compared to sham-CPAP. No difference was found regarding the determinants of gait control. This study is the first RCT to investigate the effects of CPAP on gait control. Eight weeks of CPAP treatment did not improve gait control in severe non-obese OSAS patients. These results substantiate the complex OSAS-neurocognitive function relationship.

Rationale and design of the Hyperglycemic Profiles in Obstructive Sleep Apnea (HYPNOS) trial

The Hyperglycemic Profiles in Obstructive Sleep Apnea (HYPNOS) randomized clinical trial was conducted in adults with type 2 diabetes and moderate-to-severe obstructive sleep apnea (OSA) to determine whether treatment with positive airway pressure (PAP) therapy is associated with improvements in glycemic measures. Participants were randomly assigned to PAP therapy with lifestyle counseling or lifestyle counseling alone. While observational and experimental evidence indicate that intermittent hypoxemia and recurrent arousals in OSA may alter glucose metabolism and worsen glycemic measures, the effect of treating OSA with PAP therapy on these measures in type 2 diabetes is uncertain. Adequately powered randomized clinical trials have yet to be performed to demonstrate whether PAP therapy for OSA in patients with type 2 diabetes can improve glycemic measures. The HYPNOS trial was designed to determine whether PAP therapy for OSA in patients with type 2 diabetes over 3 months leads to improvements in glycemic measures including glycemic variability (standard deviation) based on Dexcom G4 Platinum continuous glucose monitoring. Secondary objectives were to assess the effects of PAP therapy for OSA on measures of: (1) glycemic variability based on Abbott Freestyle Pro Libre continuous glucose monitoring; (2) point-of-care hemoglobin A1c (HbA1c); (3) degree of post-prandial hyperglycemia as determined by 7-point self-monitoring of blood glucose; (4) clinic and ambulatory blood pressure; and (5) endothelial function. The HYPNOS trial was designed to address gaps in our understanding of the effects of PAP therapy on glucose metabolism in adults with type 2 diabetes and moderate-to-severe OSA. Trial Registration: ClinicalTrials.gov Identifier NCT02454153.

Meta-analysis of changes in the levels of catecholamines and blood pressure with continuous positive airway pressure therapy in obstructive sleep apnea

Stress from obstructive sleep apnea (OSA) stimulates catecholamine release consequently exacerbating hypertension. However, different studies have shown a conflicting impact of continuous positive airway pressure (CPAP) treatment in patients with OSA on catecholamine levels and blood pressure. We aimed to examine changes to catecholamine levels and blood pressure in response to CPAP treatment. We conducted a meta‐analysis of data published up to May 2020. The quality of the studies was evaluated using standard tools for assessing the risk of bias. Meta‐analysis was conducted using RevMan (v5.3) and expressed in standardized mean difference (SMD) for catecholamines and mean difference (MD) for systolic (SBP) and diastolic blood pressure (DBP). A total of 38 studies met our search criteria; they consisted of 14 randomized control trials (RCT) totaling 576 participants and 24 prospective cohort studies (PCS) of 547 participants. Mean age ranged between 41 and 62 year and body mass index between 27.2 and 35.1 kg/m². CPAP treatment reduced 24‐hour urinary noradrenaline levels both in RCT (SMD = −1.1; 95% confidence interval (CI): −1.63 to − 0.56) and in PCS (SMD = 0.38 (CI: 0.24 to 0.53). SBP was also reduced by CPAP treatment in RCT (4.8 mmHg; CI: 2.0‐7.7) and in PCS (7.5 mmHg; CI: 3.3‐11.7). DBP was similarly reduced (3.0 mmHg; CI: 1.4‐4.6) and in PCS (5.1 mmHg; CI: 2.3‐8.0). In conclusion, CPAP treatment in patients with OSA reduces catecholamine levels and blood pressure. This suggests that sympathetic activity plays an intermediary role in hypertension associated with OSA‐related stress.

The role of sham continuous positive airway pressure as a placebo in controlled trials: Best Apnea Interventions for Research Trial

STUDY OBJECTIVES

The main objective of this study was to evaluate the role of sham continuous positive airway pressure (CPAP) compared to conservative medical therapy (CMT) as a control arm in the Best Apnea Interventions for Research (BestAIR) study by assessing differences in subjectively and objectively measured outcomes, adverse events, adherence, and retention rates.

METHODS

BestAIR is a clinical trial aimed to identify important design features for future randomized controlled trials of CPAP. Participants with obstructive sleep apnea were randomized to one of four groups; two control arms (CMT, sham-CPAP) and two active CPAP arms (with and without behavioral interventions). Blood pressure and health-related quality of life outcomes were assessed at baseline, 6 and 12 months. Study outcomes, retention, and adverse event rates were compared between the two control arms. Sham-CPAP adherence and self-efficacy were also compared to active-CPAP adherence (without behavioral intervention).

RESULTS

Our sample included 86 individuals in the control arms and 42 participants in the active-CPAP arm. There were no differences in longitudinal profiles in blood pressure, health-related quality of life outcomes, dropout rates, or adverse events in sham-CPAP group compared to CMT-only group (all ps > 0.05); standardized differences were generally small and with inconsistent directionality across measurements. When compared to active-CPAP, sham-CPAP was associated with 93 fewer minutes/night of usage over 12 months (p = 0.007) and lower outcome expectations (p < 0.05).

CONCLUSION

We observed no evidence of differences in objectively or subjectively measured outcomes with the use of sham-CPAP compared to CMT group. The lower adherence on sham-CPAP and poorer self-efficacy compared to active-CPAP may suggest differences in perceived benefit.

REGISTRATION

NCT01261390 Best Apnea Interventions for Research (BestAIR) www.clinicaltrials.gov.

A Randomized, Controlled, Pilot Study of CPAP for Patients with Chronic Cough and Obstructive Sleep Apnea

BACKGROUND

An association between chronic cough and obstructive sleep apnea (OSA) has been reported in prior studies with resolution or improvement in cough after continuous positive airway pressure (CPAP) therapy. Controlled studies of the benefit of CPAP on cough-quality of life measures have not been conducted.

RESEARCH QUESTION

Does CPAP therapy for OSA improve cough in patients with chronic unexplained cough?

STUDY DESIGN AND METHODS

Patients with unexplained chronic cough (> 2 months duration of cough) and OSA were randomized to receive either CPAP or sham CPAP therapy for 6 weeks. The primary end point was the change in health status assessed with the Leicester Cough Questionnaire (LCQ) in patients treated with CPAP vs. sham CPAP. Secondary end points were changes in exhaled breath condensate markers of airway inflammation (interleukin-6, nitrite/nitrates, hydrogen peroxide and 8-isoprostanes).

RESULTS

A total of 22 patients with chronic unexplained cough and OSA were randomized of whom18 completed 6 weeks of treatments with either CPAP or sham CPAP. The CPAP vs. sham CPAP-treated group were comparable in terms of sex distribution, body mass index, and OSA severity. Following CPAP therapy, there was a significantly greater improvement in total LCQ scores as compared to those treated with sham therapy (ANCOVA p value 0.016). No significant differences were noted in the exhaled breath condensate marker changes between CPAP-treated vs. sham CPAP-treated groups.

CONCLUSION

Treatment of comorbid OSA in patients with chronic cough improved cough quality of life measures following treatment of OSA with CPAP in this pilot study. Larger studies to understand this association and unravel mechanisms of CPAP benefit in chronic cough need to be undertaken. Clinical Trial Registration NCT03172130.

Continuous positive airway pressure versus standard care for the treatment of people with mild obstructive sleep apnoea (MERGE): a multicentre, randomised controlled trial

BACKGROUND

The evidence base for the treatment of mild obstructive sleep apnoea is limited and definitions of disease severity vary. The MERGE trial investigated the clinical effectiveness of continuous positive airway pressure in patients with mild obstructive sleep apnoea.

METHODS

MERGE, a multicentre, parallel, randomised controlled trial enrolled patients (≥18 years to ≤80 years) with mild obstructive sleep apnoea (apnoea-hypopnoea index [AHI] ≥5 to ≤15 events per h using either AASM 2007 or AASM 2012 scoring criteria) from 11 UK sleep centres. Participants were assigned (1:1) to either 3 months of continuous positive airway pressure plus standard care (sleep counselling), or standard care alone, by computer-generated randomisation; neither participants nor researchers were blinded. The primary outcome was a change in the score on the Short Form-36 questionnaire vitality scale in the intention-to-treat population of patients with mild obstructive sleep apnoea diagnosed using the American Academy of Sleep Medicine 2012 scoring criteria. The study is registered with ClinicalTrials.gov, NCT02699463.

FINDINGS

Between Nov 28, 2016 and Feb 12, 2019, 301 patients were recruited and randomised. 233 had mild obstructive sleep apnoea using AASM 2012 criteria and were included in the intention-to-treat analysis: 115 were allocated to receive continuous positive airway pressure and 118 to receive standard care. 209 (90%) of these participants completed the trial. The vitality score significantly increased with a treatment effect of a mean of 10·0 points (95% CI 7·2-12·8; p<0·0001) after 3 months of continuous positive airway pressure, compared with standard care alone (9·2 points [6·8 to 11·6] vs -0·8 points [-3·2 to 1·5]). Using the ANCOVA last-observation-carried-forward analysis, a more conservative estimate, the vitality score also significantly increased with a treatment effect of a mean of 7·5 points (95% CI 5·3 to 9·6; p<0·0001) after 3 months of continuous positive airway pressure, compared with standard care alone (7·5 points [6·0 to 9·0] vs 0·0 points [-1·5 to 1·5]). Three serious adverse events occurred (one allocated to the continuous positive airway pressure group) and all were unrelated to the intervention.

INTERPRETATION

3 months of treatment with continuous positive airway pressure improved the quality of life in patients with mild obstructive sleep apnoea. These results highlight the need for health-care professionals and providers to consider treatment for patients with mild obstructive sleep apnoea.

FUNDING

ResMed Ltd.

A randomized controlled trial on ambulatory blood pressure lowering effect of CPAP in patients with obstructive sleep apnea and nocturnal hypertension

Objective: In a randomised controlled trial, we investigated the blood pressure (BP) lowering effect of continuous positive airway pressure (CPAP) in patients with moderate-severe obstructive sleep apnoea syndrome (OSAS, an apnoea-hypopnoea index, AHI of 15 or higher) and nocturnal hypertension (night-time systolic/diastolic BP ≥120/70 mmHg).Methods: Sixty patients were randomly assigned to CPAP or sham CPAP, while maintaining their antihypertensive treatment. Ambulatory BP monitoring was performed at baseline (first run-in visit) and the end of follow-up. Clinic and home BP were measured at baseline and each of the monthly follow-up visits.Results: Of the 60 patients, 47 completed the 3-month study. CPAP (n = 26), compared with sham CPAP (n = 21), slightly and non-significantly reduced 24-h systolic/diastolic BP by -2.8/-2.5 mmHg (p ≥ 0.27), with a slightly greater between-group difference in the daytime (-4.0/-2.8 mmHg, p ≥ 0.29) than night-time (-0.2/-1.5 mmHg, p ≥ 0.50). The CPAP treatment did not significantly influence clinic or home BP during follow-up (p ≥ 0.27). Nonetheless, simple and partial correlation analyses showed that the ambulatory BP lowering effect was dependent on the daytime pulse rate at baseline (r ≥ 0.47, p ≤ 0.01). In patients with a daytime pulse rate greater than 85 beats/min, the mean changes in daytime systolic BP were significantly greater in the CPAP (n = 10) than sham CPAP group (n = 11), with a between-group mean difference of -10.1 mmHg (p = 0.048).Conclusions: The CPAP treatment did not show significant ambulatory BP lowering effect in patients with moderate-severe OSAS and nocturnal hypertension. However, it may be effective in lowering daytime BP in patients with a faster pulse rate.

Effects of continuous positive airway pressure on depression and anxiety symptoms in patients with obstructive sleep apnoea: results from the sleep apnoea cardiovascular Endpoint randomised trial and meta-analysis

BACKGROUND

Whether continuous positive airway pressure (CPAP) treatment can improve depression or anxiety symptoms in obstructive sleep apnoea (OSA) patients remains uncertain.

METHODS

Secondary analysis of the Sleep Apnea Cardiovascular Endpoints (SAVE) trial, combined with a systematic review of randomised evidence. The SAVE secondary analyses involved 2410 patients with co-existing moderate-severe OSA and established cardiovascular disease randomly allocated to CPAP treatment plus usual care or usual care alone and followed up for 3·7 (SD 1·6) years. We evaluated the effect of CPAP treatment on depression and anxiety caseness (scores ≥ 8 on the Hospital Anxiety and Depression Scale depression and anxiety subscales [HADS-D and HADS-A]) for OSA patients.

FINDINGS

CPAP treatment was associated with reduced odds of depression caseness (adjusted odds ratio [OR] 0·80, 95% confidence interval [CI] 0·65-0·98, P = 0·031) compared to usual care in the SAVE trial and the treatment effect was greater in those with pre-existing depression symptoms. A systematic review of 20 randomised trials including 4255 participants confirmed a benefit of CPAP in reducing depression symptoms in OSA patients: the overall effect (standardised mean difference) was - 0·18 (95% CI - 0·24 to - 0·12). No effect of CPAP treatment on anxiety caseness was found both in patients of the SAVE study (adjusted OR 0·98, 95% CI 0·78-1·24, P = 0·89) and the systematic review.

INTERPRETATION

CPAP reduces depression symptoms in patients with co-existing OSA and CVD independently of improvements in sleepiness.

Diabetes sleep treatment trial: Premise, design, and methodology

The Diabetes Sleep Treatment Trial (DSTT) is a multi-site, double-blinded, randomized, sham-controlled trial. The study objective is to test whether treatment of obstructive sleep apnea (OSA) with continuous positive airway pressure (CPAP) treatment results in improved glycemic control and diabetes self-management behavior compared to participants on a sham-CPAP (sub-therapeutic) device in participants with type 2 diabetes mellitus (T2DM) and co-morbid OSA. The purpose of this paper is to describe the premise for the DSTT, the study design, and the methodology used in this on-going trial. The target enrollment is 210 randomly assigned participants recruited from two sites. The primary outcome for glucose control is HbA1C; additional outcomes for diabetes self-management include objectively measured steps walked and subjectively measured diabetes-related distress, diabetes empowerment, and diabetes knowledge. All participants receive individual diabetes education and counseling for 6 weeks over two individual sessions and three telephone calls. Participants are randomized to receive either sham or active CPAP for 12 weeks, after which, they "guess" their group assignment; this will assist in determining the success of blinding participants to treatment group assignment. Participants revealed to be on active CPAP will be encouraged to continue CPAP for an additional 12 weeks; participants who had been on sham devices will be encouraged to have a repeat CPAP titration study and to crossover to active CPAP treatment for 24 weeks. An intention-to-treat approach will be used for efficacy analyses. The trial is registered with Clinicaltrials.gov (NCT01901055).

Peri-operative treatment of sleep-disordered breathing and outcomes in bariatric patients

Background

Obstructive sleep apnoea (OSA) is increasingly common in bariatric patients undergoing sedation during elective surgery. However, it has not been established how significant a contributor it is to peri-operative respiratory complications and mortality. We sought to pre-operatively identify OSA in bariatric patients and record peri-operative complications during and after bariatric surgery.

Methods

Data were collected and analysed from June 2014 to March 2017 for 410 bariatric surgery patients referred to the sleep laboratory for pre-operative screening and treatment of OSA. The STOP-Bang questionnaire, Epworth Sleepiness Scale (ESS) and nocturnal pulse oximetry were recorded and treatment was allocated with continuous positive airway pressure (CPAP). Peri-operative complications and mortality were the primary outcome measures for patients receiving CPAP treatment for OSA, with patients who did not require CPAP used as control. The mean follow-up time for all patients was 433 and 732 days for the patients who had undergone bariatric surgery. The two groups were compared with Chi square test and unpaired two-tailed t-test.

Results

OSA was present in any form in 70% of the screened patients; 40% of patients involved in the study received CPAP treatment. Patients receiving CPAP treatment [49.5 (11.3) years old, 61% female, 50.3 (8.5) kg/m²] were older, had a lower percentage of females and had a higher body mass index (BMI) than those not receiving CPAP [44.9 (12.0), 81% female, 46.6 (7.7)]. No significant differences were observed between patients on CPAP and those not on CPAP, there was no significant difference in hospital stay or rate of respiratory complications. Out of 53 patients who had undergone bariatric surgery at the cut-off date, only 1 had suffered a respiratory complication.

Conclusions

Bariatric patients who are screened pre-operatively for OSA and treated according to guidelines have no increased risk of respiratory complications compared to patients without OSA.

Effect of Continuous Positive Airway Pressure on Airway Reactivity in Asthma. A Randomized, Sham-controlled Clinical Trial

RATIONALE

Studies have demonstrated that application of stress suppresses airway smooth muscle contractility. In animal models of asthma, continuous positive airway pressure (CPAP) reduced airway reactivity. Short-term studies of CPAP in patients with asthma showed reductions in airway reactivity.

OBJECTIVES

To evaluate whether nocturnal CPAP decreased the provocative concentration of methacholine to reduce FEV₁ by 20% (PC₂₀).

METHODS

One hundred ninety-four individuals with asthma were randomized (1:1:1) to use CPAP with warmed, filtered, humidified air at night at pressures either less than 1 cm H₂O (sham) or at 5 cm H₂O or 10 cm H₂O. The primary outcome was change in PC₂₀ after 12 weeks.

MEASUREMENTS AND MAIN RESULTS

Adherence to CPAP was low in all groups. Regardless, all groups had a significant improvement in PC₂₀, with 12 weeks/baseline PC₂₀ ratios of 2.12, 1.73, and 1.78 for the sham, 5 cm H₂O, and 10 cm H₂O groups, respectively, and no significant differences between the active and sham groups. Changes in FEV₁ and exhaled nitric oxide were minimal in all groups. The sham group had larger improvements in most patient-reported outcomes measuring asthma symptoms and quality of life, as well as sinus symptoms, than the 5 cm H₂O group. The 10 cm H₂O group showed similar but less consistent improvements in scores, which were not different from improvements in the sham group.

CONCLUSIONS

Adherence to nocturnal CPAP was low. There was no evidence to support positive pressure as being effective for reducing airway reactivity in people with well-controlled asthma. Regardless, airway reactivity was improved in all groups, which may represent an effect of participating in a study and/or an effect of warm, humid, filtered air on airway reactivity. Clinical trial registered with www.clinicaltrials.gov (NCT01629823).

Effect of Home Noninvasive Ventilation With Oxygen Therapy vs Oxygen Therapy Alone on Hospital Readmission or Death After an Acute COPD Exacerbation: A Randomized Clinical Trial

IMPORTANCE

Outcomes after exacerbations of chronic obstructive pulmonary disease (COPD) requiring acute noninvasive ventilation (NIV) are poor and there are few treatments to prevent hospital readmission and death.

OBJECTIVE

To investigate the effect of home NIV plus oxygen on time to readmission or death in patients with persistent hypercapnia after an acute COPD exacerbation.

DESIGN, SETTING, AND PARTICIPANTS

A randomized clinical trial of patients with persistent hypercapnia (Paco2 >53 mm Hg) 2 weeks to 4 weeks after resolution of respiratory acidemia, who were recruited from 13 UK centers between 2010 and 2015. Exclusion criteria included obesity (body mass index [BMI] >35), obstructive sleep apnea syndrome, or other causes of respiratory failure. Of 2021 patients screened, 124 were eligible.

INTERVENTIONS

There were 59 patients randomized to home oxygen alone (median oxygen flow rate, 1.0 L/min [interquartile range {IQR}, 0.5-2.0 L/min]) and 57 patients to home oxygen plus home NIV (median oxygen flow rate, 1.0 L/min [IQR, 0.5-1.5 L/min]). The median home ventilator settings were an inspiratory positive airway pressure of 24 (IQR, 22-26) cm H2O, an expiratory positive airway pressure of 4 (IQR, 4-5) cm H2O, and a backup rate of 14 (IQR, 14-16) breaths/minute.

MAIN OUTCOMES AND MEASURES

Time to readmission or death within 12 months adjusted for the number of previous COPD admissions, previous use of long-term oxygen, age, and BMI.

RESULTS

A total of 116 patients (mean [SD] age of 67 [10] years, 53% female, mean BMI of 21.6 [IQR, 18.2-26.1], mean [SD] forced expiratory volume in the first second of expiration of 0.6 L [0.2 L], and mean [SD] Paco2 while breathing room air of 59 [7] mm Hg) were randomized. Sixty-four patients (28 in home oxygen alone and 36 in home oxygen plus home NIV) completed the 12-month study period. The median time to readmission or death was 4.3 months (IQR, 1.3-13.8 months) in the home oxygen plus home NIV group vs 1.4 months (IQR, 0.5-3.9 months) in the home oxygen alone group, adjusted hazard ratio of 0.49 (95% CI, 0.31-0.77; P = .002). The 12-month risk of readmission or death was 63.4% in the home oxygen plus home NIV group vs 80.4% in the home oxygen alone group, absolute risk reduction of 17.0% (95% CI, 0.1%-34.0%). At 12 months, 16 patients had died in the home oxygen plus home NIV group vs 19 in the home oxygen alone group.

CONCLUSIONS AND RELEVANCE

Among patients with persistent hypercapnia following an acute exacerbation of COPD, adding home noninvasive ventilation to home oxygen therapy prolonged the time to readmission or death within 12 months.

TRIAL REGISTRATION

clinicaltrials.gov Identifier: NCT00990132.

Asthma outcomes improve with continuous positive airway pressure for obstructive sleep apnea

BACKGROUND

Continuous positive airway pressure (CPAP) in asthma patients with concomitant obstructive sleep apnea syndrome (OSAS) seems to have a favorable impact on asthma, but data are inconsistent due to methodological limitations of previous studies.

METHODS

Prospective, multicenter study. We examined asthma outcomes after 6 months of CPAP in 99 adult asthma patients (mean age 57 years) with OSAS (respiratory disturbance index ≥20). Asthma control and quality of life were assessed with the Asthma Control Questionnaire (ACQ) and the Mini Asthma Quality of Life Questionnaire (MiniAQLQ), respectively. Data were analyzed by intention-to-treat basis.

RESULTS

The mean ± SD score of the ACQ decreased from 1.39 ± 0.91 at baseline to 1.0 ± 0.78 at 6 months (P = 0.003), the percentage of patients with uncontrolled asthma from 41.4% to 17.2% (P = 0.006), and the percentage of patients with asthma attacks in the 6 months before and after treatment from 35.4% to 17.2% (P = 0.015). The score of the mAQLQ increased from 5.12 ± 1.38 to 5.63 ± 1.17 (P = 0.009). There were also significant improvements in symptoms of gastroesophageal reflux and rhinitis, bronchial reversibility, and exhaled nitric oxide values (all P < 0.05). No significant changes were observed in drug therapy for asthma or their comorbidities nor in the patients' weight.

CONCLUSIONS

Asthma control (both actual and future risk), quality of life, and lung function improved after starting continuous positive airway pressure in asthmatics with moderate to severe obstructive sleep apnea syndrome.

Nasal Dilator Strip is an Effective Placebo Intervention for Severe Obstructive Sleep Apnea

STUDY OBJECTIVES

The aim of this study was to evaluate the effects of nasal dilator strip (NDS) as a placebo intervention compared with continuous positive airway pressure (CPAP) treatment in patients with severe obstructive sleep apnea (OSA).

METHODS

Patients were treated with both NDS and nasal CPAP. The sequence was randomized and interposed by 15 days of washout. Polysomnography was performed at baseline and on the first night of intervention with NDS and CPAP (titration). The Epworth Sleepiness Scale (ESS), Functional Outcomes of Sleep Questionnaire (FOSQ), and Beck Depression Inventory (BDI) were completed at baseline and at the end of both interventions. A questionnaire on the comfort and satisfaction (0 = no to 10 = total) was completed at the end of each intervention.

RESULTS

Twenty-six patients with OSA were evaluated (19 male; age 46.3 ± 9.3 y; body mass index 33.2 ± 5.1 kg/m²; ESS 15.8 ± 4.1; apnea-hypopnea index 60.7 ± 25.2). Adherence was high in both NDS (98%) and CPAP interventions (94%; 5.8 ± 1.7 h/night). In contrast to the baseline values, NDS intervention had no significant effect on all polysomnographic parameters, but NDS improved somnolence (ESS 13.0 ± 5.4, p = 0.001) and depressive symptoms (BDI 7.7 ± 6.9, p = 0.005). Reported satisfaction was significantly higher for CPAP than for NDS (sleep quality 9.2 ± 0.8 vs. 6.1 ± 2.1; wake up at morning: 8.6 ± 1.2 vs. 6.0 ± 2.2; daily activities: 8.9 ± 1.4 vs. 5.8 ± 1.5; quality of life: 8.3 ± 2.1 vs. 3.8 ± 3.5, p < 0.001), but similar low levels of difficulty for both interventions were observed (1.3 ± 2.2 vs. 0.3 ± 1.3, p = 0.098).

CONCLUSIONS

Our data indicate that NDS is an attractive placebo intervention for randomized controlled trials evaluating the effects of CPAP in sleepy patients with OSA.

Effects of continuous positive airway pressure on energy intake in obstructive sleep apnea: A pilot sham-controlled study

Obesity is among the leading risk factors for obstructive sleep apnea (OSA). A reciprocal relationship between obesity and OSA has been proposed, which may be due to excessive food intake. We conducted a pilot study to test the effects of continuous positive airway pressure (CPAP) on energy intake (EI) in OSA patients using a sham-controlled crossover design. In-laboratory total daily EI was assessed after 2mo of active and sham CPAP. Four men were enrolled (age±SEM: 51.8±2.1y; body mass index: 31.5±1.5kg/m²). All received active treatment first. Meals (breakfast, lunch, dinner, snack) were served in excess portions at fixed times and additional palatable snacks were freely available throughout the day. Total EI was lower after active (3744±511kcal/d) vs. sham (4030±456kcal/d) CPAP but this difference was not significant (p=0.51) due to variability in the free snack intake. When only fixed eating occasions were considered, daily EI was significantly lower in the active (3105±513kcal/d) vs. sham (3559±420kcal/d) condition (p=0.006). This small pilot and feasibility study is the first to utilize a sham-controlled design to investigate the effects of CPAP treatment on objective measures of EI. Findings suggest that CPAP may cause a reduction in fixed meal intake. In demonstrating feasibility of study methodology, our study also suggests a larger randomized sham-controlled trial be conducted to fully characterize the effects of CPAP treatment on EI and energy balance overall.

Effects of continuous positive airway pressure on energy balance regulation: a systematic review

Obesity is both a cause and a possible consequence of obstructive sleep apnoea (OSA), as OSA seems to affect parameters involved in energy balance regulation, including food intake, hormonal regulation of hunger/satiety, energy metabolism and physical activity. It is known that weight loss improves OSA, yet it remains unclear why continuous positive airway pressure (CPAP) often results in weight gain.The goal of this systematic review is to explore if and how CPAP affects the behaviour and/or metabolism involved in regulating energy balance.CPAP appears to correct for a hormonal profile characterised by abnormally high leptin and ghrelin levels in OSA, by reducing the circulating levels of each. This is expected to reduce excess food intake. However, reliable measures of food intake are lacking, and not yet sufficient to make conclusions. Although studies are limited and inconsistent, CPAP may alter energy metabolism, with reports of reductions in resting metabolic rate or sleeping metabolic rate. CPAP appears to not have an appreciable effect on altering physical activity levels. More work is needed to characterise how CPAP affects energy balance regulation.It is clear that promoting CPAP in conjunction with other weight loss approaches should be used to encourage optimal outcomes in OSA patients.

Trial of early noninvasive ventilation for ALS: A pilot placebo-controlled study

OBJECTIVE

To evaluate the use and tolerability of noninvasive positive pressure ventilation (NIV) in patients with amyotrophic lateral sclerosis (ALS) early in their disease by comparing active NIV and sham NIV in patients not yet eligible for NIV use as recommended by practice guidelines.

METHODS

This was a single-center, prospective, double-blind, randomized, placebo (sham)-controlled pilot trial. Patients with ALS were randomized to receive either sham NIV or active NIV and underwent active surveillance approximately every 3 months until they reached a forced vital capacity (FVC) <50% or required NIV for clinical symptom management.

RESULTS

In total, 54 participants were randomized. The mean NIV use was 2.0 hours (95% confidence interval [CI] 1.1-3.0) per day in the sham NIV treatment group and 3.3 hours (CI 2.0-4.6) per day in the active NIV group, which did not differ by treatment group (p = 0.347). The majority of sham NIV participants (88%) and active NIV participants (73%) reported only mild or no problem with NIV use. Difference of change in FVC through the treatment period by group (0.44 per month) favored active NIV (p = 0.049). Survival and changes in maximal inspiratory or expiratory pressure did not differ between treatment groups.

CONCLUSIONS

The efficacy of early NIV in ALS should be tested in randomized, placebo-controlled trials. The trial is registered on clinicaltrials.gov (NCT00580593).

CLASSIFICATION OF EVIDENCE

This study provides Class II evidence that for patients with ALS, adherence with NIV and sham NIV are similar.

Effect of CPAP therapy on cardiovascular events and mortality in patients with obstructive sleep apnea: a meta-analysis

PURPOSE

Continuous positive airway pressure (CPAP) therapy may decrease the risk of mortality and cardiovascular events in patients with obstructive sleep apnea. However, these benefits are not completely clear.

METHODS

We undertook a meta-analysis of randomized clinical trials identified in systematic searches of MEDLINE, EMBASE, and the Cochrane Database.

RESULTS

Eighteen studies (4146 patients) were included. Overall, CPAP therapy did not significantly decrease the risk of cardiovascular events compared with the control group (odds ratio (OR), 0.84; 95 % confidence intervals (CI), 0.62-1.13; p = 0.25; I (2) = 0 %). CPAP was associated with a nonsignificant trend of lower rate of death and stroke (for death: OR, 0.85; 95 % CI, 0.35-2.06; p = 0.72; I (2) = 0.0 %; for stroke: OR, 0.56; 95 % CI, 0.18-1.73; p = 0.32; I (2) = 12.0 %), a significantly lower Epworth sleepiness score (ESS) (mean difference (MD), -1.78; 95 % CI, -2.31 to -1.24; p < 0.00001; I (2) = 76 %), and a significantly lower 24 h systolic and diastolic blood pressure (BP) (for 24 h systolic BP: MD, -2.03 mmHg; 95 % CI, -3.64 to -0.42; p = 0.01; I (2) = 0 %; for diastolic BP: MD, -1.79 mmHg; 95 % CI, -2.89 to -0.68; p = 0.001; I (2) = 0 %). Daytime systolic BP and body mass index were comparable between the CPAP and control groups. Subgroup analysis did not show any significant difference between short- and mediate-to-long-term follow-up groups with regard to cardiovascular events, death, and stroke.

CONCLUSIONS

CPAP therapy was associated with a trend of decreased risk of cardiovascular events. Furthermore, ESS and BP were significantly lower in the CPAP group. Larger randomized studies are needed to confirm these findings.

Eight Hours of Nightly Continuous Positive Airway Pressure Treatment of Obstructive Sleep Apnea Improves Glucose Metabolism in Patients with Prediabetes. A Randomized Controlled Trial

RATIONALE

Although obstructive sleep apnea (OSA) is associated with impaired glucose tolerance and diabetes, it remains unclear whether OSA treatment with continuous positive airway pressure (CPAP) has metabolic benefits.

OBJECTIVES

To determine the effect of 8-hour nightly CPAP treatment on glucose metabolism in individuals with prediabetes and OSA.

METHODS

In a randomized controlled parallel group study, 39 participants were randomly assigned to receive either 8-hour nightly CPAP (n = 26) or oral placebo (n = 13). Sleep was polysomnographically recorded in the laboratory on each night. CPAP adherence was ensured by continuous supervision. Participants continued their daily routine activities outside the laboratory. Glucose metabolism was assessed at baseline and after 2 weeks of assigned treatment using both the oral and intravenous glucose tolerance tests. The primary outcome was the overall glucose response as quantified by the area under the curve for glucose during 2-hour oral glucose tolerance testing. Secondary outcomes included fasting and 2-hour glucose and insulin, the area under the curves for insulin and insulin secretion, norepinephrine, insulin sensitivity, acute insulin response to glucose, and 24-hour blood pressure.

MEASUREMENTS AND MAIN RESULTS

The overall glucose response was reduced (treatment difference: -1,276.9 [mg/dl] · min [95% confidence interval, -2,392.4 to -161.5]; P = 0.03) and insulin sensitivity was improved (treatment difference: 0.77 [mU/L](-1) · min(-1) [95% confidence interval, 0.03-1.52]; P = 0.04) with CPAP as compared with placebo. Additionally, norepinephrine levels and 24-hour blood pressure were reduced with CPAP as compared with placebo.

CONCLUSIONS

In patients with prediabetes, 8-hour nightly CPAP treatment for 2 weeks improves glucose metabolism compared with placebo. Thus, CPAP treatment may be beneficial for metabolic risk reduction. Clinical trial registered with www.clinicaltrials.gov (NCT 01156116).

Effects of exercise training on sleep apnea: a meta-analysis

BACKGROUND

Several studies have shown a favorable effect of supervised exercise training on obstructive sleep apnea (OSA). This meta-analysis was conducted to analyze the data from these studies on the severity of OSA (primary outcome) in adults. Secondary outcomes of interest included body mass index (BMI), sleep efficiency, daytime sleepiness and cardiorespiratory fitness.

METHODS

Two independent reviewers searched PubMed and Embase (from inception to March 6, 2013) to identify studies on the effects of supervised exercise training in adults with OSA. Pre- and postexercise training data on our primary and secondary outcomes were extracted.

RESULTS

A total of 5 studies with 6 cohorts that enrolled a total of 129 study participants met the inclusion criteria. The pooled estimate of mean pre- to postintervention (exercise) reduction in AHI was −6.27 events/h (95 % confidence interval [CI] -8.54 to -3.99; p < 0.001). The pooled estimates of mean changes in BMI, sleep efficiency, Epworth sleepiness scale and VO2 peak were -1.37 (95 % CI −2.81 to 0.07; p = 0.06), 5.75 % (95 % CI 2.47-9.03; p = 0.001), -3.3 (95 % CI -5.57 to -1.02; p = 0.004), and 3.93 mL/kg/min (95 % CI 2.44-5.42; p < 0.001), respectively.

CONCLUSIONS

This meta-analysis shows a statistically significant effect of exercise in reducing the severity of sleep apnea in patients with OSA with minimal changes in body weight. Additionally, the significant effects of exercise on cardiorespiratory fitness, daytime sleepiness, and sleep efficiency indicate the potential value of exercise in the management of OSA.

Comparative effectiveness research in obstructive sleep apnea: bridging gaps between efficacy studies and clinical practice

Comparative effectiveness research encompasses research that compares two interventions to each other, and takes place in real-world settings without strict inclusion and exclusion criteria, according to the established standard of care. There is a need for comparative evaluations of the treatments for obstructive sleep apnea, a disease associated with increased cardiovascular risk, stroke and metabolic derangement. This article reviews the recent, representative literature that addresses obstructive sleep apnea intervention and treatment, paradigms for diagnosis and randomized control trials addressing the efficacy of interventions, in an effort to demonstrate examples of both traditional observational and randomized control trials, as well as to illustrate the considerable overlap between some traditional studies and comparative effectiveness research. Despite methodological challenges, the potentially large clinical and public health impact of obstructive sleep apnea, accompanied by considerable cost, mandates that randomized controlled trials and comparative effectiveness research be systematically applied to identify both the efficacy and effectiveness of alternative diagnosis and treatment strategies.

CPAP, weight loss, or both for obstructive sleep apnea

BACKGROUND

Obesity and obstructive sleep apnea tend to coexist and are associated with inflammation, insulin resistance, dyslipidemia, and high blood pressure, but their causal relation to these abnormalities is unclear.

METHODS

We randomly assigned 181 patients with obesity, moderate-to-severe obstructive sleep apnea, and serum levels of C-reactive protein (CRP) greater than 1.0 mg per liter to receive treatment with continuous positive airway pressure (CPAP), a weight-loss intervention, or CPAP plus a weight-loss intervention for 24 weeks. We assessed the incremental effect of the combined interventions over each one alone on the CRP level (the primary end point), insulin sensitivity, lipid levels, and blood pressure.

RESULTS

Among the 146 participants for whom there were follow-up data, those assigned to weight loss only and those assigned to the combined interventions had reductions in CRP levels, insulin resistance, and serum triglyceride levels. None of these changes were observed in the group receiving CPAP alone. Blood pressure was reduced in all three groups. No significant incremental effect on CRP levels was found for the combined interventions as compared with either weight loss or CPAP alone. Reductions in insulin resistance and serum triglyceride levels were greater in the combined-intervention group than in the group receiving CPAP only, but there were no significant differences in these values between the combined-intervention group and the weight-loss group. In per-protocol analyses, which included 90 participants who met prespecified criteria for adherence, the combined interventions resulted in a larger reduction in systolic blood pressure and mean arterial pressure than did either CPAP or weight loss alone.

CONCLUSIONS

In adults with obesity and obstructive sleep apnea, CPAP combined with a weight-loss intervention did not reduce CRP levels more than either intervention alone. In secondary analyses, weight loss provided an incremental reduction in insulin resistance and serum triglyceride levels when combined with CPAP. In addition, adherence to a regimen of weight loss and CPAP may result in incremental reductions in blood pressure as compared with either intervention alone. (Funded by the National Heart, Lung, and Blood Institute; ClinicalTrials.gov number, NCT0371293 .).

Interactions between sleep, circadian function, and glucose metabolism: implications for risk and severity of diabetes

Sleep disturbances, including sleep insufficiency and sleep fragmentation, have been linked to abnormal glucose metabolism and increased diabetes risk. Well-controlled laboratory studies have provided insights regarding the underlying mechanisms. Several large prospective studies suggest that these sleep disturbances are associated with an increased risk of incident diabetes. Obstructive sleep apnea, which combines sleep fragmentation and hypoxemia, is a major risk factor for insulin resistance and possibly diabetes. Whether glycemic control in type 2 diabetes patients can be improved by treating sleep apnea remains controversial. Recently, sleep disturbances during pregnancy and their relationship to gestational diabetes and hyperglycemia have received considerable attention owing to potential adverse effects on maternal and fetal health. Additionally, evidence from animal models has identified disruption of the circadian system as a putative risk factor for adverse metabolic outcomes. The purpose of this review is to provide an update on the current state of knowledge linking sleep disturbances, circadian dysfunction, and glucose metabolism. Experimental, prospective, and interventional studies are discussed.

The effect of sleep disordered breathing on the outcome of stroke and transient ischemic attack: a systematic review

STUDY OBJECTIVES

The primary objective was to systematically review the literature on how sleep disordered breathing (SDB) affects recurrence and death among stroke or transient ischemic attack (TIA) patients. A secondary objective was to evaluate how treatment of SDB with continuous positive airway pressure (CPAP) affects the risk of recurrence and death in these patients.

METHODS

Adults (18+) with a stroke or TIA diagnosis were eligible for inclusion. Case groups consisted of patients with a sleep disorder. The outcomes of interest were all-cause mortality, recurrent vascular events, and case fatality.

RESULTS

Ten articles covering 1,203 stroke and TIA patients were included in the review. The results generally support a dose-response relationship between severity of SDB and risk of recurrent events and all-cause mortality in stroke and TIA patients. Three small-scale articles with substantial risk of bias evaluated the effects of CPAP therapy, and the results are inconclusive. Data on case fatality is too sparse to be conclusive.

CONCLUSIONS

Existing studies provide sufficient data to establish obstructive SDB as a negative predictor of all-cause mortality and recurrent vascular events following stroke or TIA. The ability of CPAP treatment to lower the risk of serious adverse outcomes after stroke remains controversial because of substantial risk of bias identified in most of the eligible studies addressing this relation. Additional studies are needed.

Continuous positive airway pressure improves sleep and daytime sleepiness in patients with Parkinson disease and sleep apnea

STUDY OBJECTIVES

Obstructive sleep apnea (OSA), common in Parkinson disease (PD), contributes to sleep disturbances and daytime sleepiness. We assessed the effect of continuous positive airway pressure (CPAP) on OSA, sleep, and daytime sleepiness in patients with PD.

DESIGN

This was a randomized placebo-controlled, crossover design. Patients with PD and OSA were randomized into 6 w of therapeutic treatment or 3 w of placebo followed by 3 w of therapeutic treatment. Patients were evaluated by polysomnography (PSG) and multiple sleep latency test (MSLT) pretreatment (baseline), after 3 w, and after 6 w of CPAP treatment. Analyses included mixed models, paired analysis, and within-group analyses comparing 3 w to 6 w of treatment.

SETTING

Sleep laboratory.

PARTICIPANTS

Thirty-eight patients with PD (mean age = 67.2 ± 9.2 y; 12 females).

INTERVENTION

Continuous positive airway pressure.

MEASUREMENTS

PSG OUTCOME MEASURES: sleep efficiency, %sleep stages (N1, N2, N3, R), arousal index, apnea-hypopnea index (AHI), and % time oxygen saturation < 90% (%time SaO2 < 90%). MSLT outcome measures: mean sleep-onset latency (MSL).

RESULTS

There were significant group-by-time interactions for AHI (P < 0.001), % time SaO2 < 90% (P = 0.02), %N2 (P = 0.015) and %N3 (P = 0.014). Subjects receiving therapeutic CPAP showed significant decrease in AHI, %time SaO2 < 90%, %N2, and significant increase in %N3 indicating effectiveness of CPAP in the treatment of OSA, improvement in nighttime oxygenation, and in deepening sleep. The paired sample analyses revealed that 3 w of therapeutic treatment resulted in significant decreases in arousal index (t = 3.4, P = 0.002). All improvements after 3 w were maintained at 6 w. Finally, 3 w of therapeutic CPAP also resulted in overall decreases in daytime sleepiness (P = 0.011).

CONCLUSIONS

Therapeutic continuous positive airway pressure versus placebo was effective in reducing apnea events, improving oxygen saturation, and deepening sleep in patients with Parkinson disease and obstructive sleep apnea. Additionally, arousal index was reduced and effects were maintained at 6 weeks. Finally, 3 weeks of continuous positive airway pressure treatment resulted in reduced daytime sleepiness measured by multiple sleep latency test. These results emphasize the importance of identifying and treating obstructive sleep apnea in patients with Parkinson disease.

Improving activity in adults with diabetes and coexisting obstructive sleep apnea

This study in participants with type 2 diabetes and obstructive sleep apnea evaluated changes in activity, sleep quality, and daytime sleepiness after 4 weeks of continuous positive airway pressure (CPAP). This pilot study was a double-blind, randomized, placebo-controlled trial. Sleep apnea was quantified with an overnight sleep study. Sleep quality was measured by the Pittsburgh Sleep Quality Index, daytime sleepiness by the Epworth Sleepiness Scale, vigor and fatigue with the Profiles of Mood States, subjective activity with the Functional Outcomes of Sleep Questionnaire, and objective activity with the Bodymedia SenseWear Armband. Subjects were randomized to either CPAP (n = 12) or sham-devices (n = 11). The intervention group had reduced apneas and hypopneas, daytime sleepiness, and fatigue; they also had improved sleep quality and increased objective activity and vigor. The study suggested that treatment of obstructive sleep apnea results in a modest improvement of activity in persons with type 2 diabetes.

Agreement in computer-assisted manual scoring of polysomnograms across sleep centers

STUDY OBJECTIVES

To determine intersite agreement in respiratory event scoring of polysomnograms (PSGs) using different hypopnea definitions.

DESIGN

Technical assessment.

SETTING

Five academic medical centers.

PARTICIPANTS

N/A.

INTERVENTIONS

N/A.

MEASUREMENTS AND RESULTS

Seventy good-quality PSGs performed in middle-aged women were manually scored by two experienced technologists at each of the five sleep centers using the particular laboratory's own software system. Studies were scored once by each scorer using American Academy of Sleep Medicine (AASM) standards for scoring sleep stages, arousals, and apneas. Hypopneas were then scored using three different AASM criteria: recommended, alternate, and research (Chicago). Means of each PSG variable for the scorers at each site were used to calculate an across-site intraclass correlation coefficient (ICC). Average AHI across the 10 scorers was 7.4 ± 12.3 (standard deviation) events/h using recommended criteria (ICC 0.984; 95% confidence interval [CI] 0.977-0.990), 12.1 ± 13.3 events/h using alternate criteria (ICC 0.947; 95% CI 0.889-0.972), and 15.1 ± 13.9 events/h with Chicago criteria (ICC 0.800; 95% CI 0.768-0.828). ICC across sites was 0.870 (95% CI = 0.847-0.889) for total sleep time, 0.861 (95% CI 0.837-0.881) for number of obstructive apneas and 0.683 (95% CI 0.640-0.722) for number of central apneas. ICCs across sites for hypopneas were very good using recommended criteria (ICC 0.843; 95% CI 0.820-0.870) but decreased when alternate criteria (ICC 0.728; 95% CI 0.689-0.763) and Chicago criteria (ICC 0.535; 95% CI 0.485-0.583) were used.

CONCLUSION

Experienced scorers at different laboratories have very good agreement in hypopnea and AHI results when good-quality PSGs are scored using AASM-recommended criteria. Substantial degradation of reliability was observed for alternative definitions of hypopneas, particularly that proposed for research.

Effects of continuous positive airway pressure on endothelial function and circulating progenitor cells in obstructive sleep apnoea: a randomised sham-controlled study

OBJECTIVE

Obstructive sleep apnoea (OSA) is characterised by reoccurring apnoeas and hypopneas, causing repetitive hypoxia and reoxygenation, and is associated with endothelial dysfunction and reduced levels of circulating progenitor cells (CPCs). The potential to improve endothelial function and CPC levels in people with OSA by preventing hypoxic episodes with Continuous Positive Airway Pressure (CPAP) was investigated in a sham-controlled CPAP study.

METHODS

Men with moderate-to-severe OSA (mean ± SD: age=49 ± 12 y, apnoea hypopnea index (AHI)=37.6 ± 16.4 events/h, body mass index=31.5 ± 5.7 kg/m(2)) who were CPAP naïve without diabetes mellitus were randomised in a 12-week double-blind sham-controlled parallel group study to receive either active (n=25) or sham (n=21) CPAP. CPCs, isolated from blood, were measured by flow cytometry and by co-staining cultured cells (7 days) with acetylated low-density lipoprotein (acLDL) and lectin. Endothelial function was assessed by peripheral arterial tonometry (PAT).

RESULTS

Compared to sham, CPAP significantly decreased AHI (mean between-group difference -36.0 events/h; 95%CI, -49.7 to -22.3, p<0.0001) after 12 weeks. Despite this improvement in AHI, CPAP had no effect on change in CPC levels (including CD34(+)/KDR(+) (565 cells/mL; -977 to 2106, p=0.45), CD34(+)/KDR(+)/CD45(-) (37.0 cells/mL; -17.7 to 85.7, p=0.13), acLDL(+)/lectin(+) (-43.1 cells/field, -247 to 161, p=0.67)) or change in endothelial function (0.27; -0.14 to 0.67, p=0.19) compared to sham therapy.

CONCLUSIONS

Despite the improvement in OSA parameters and ablation of apnoeic events by CPAP, CPC counts and endothelial function in men with moderate-to-severe OSA were not significantly improved after 12 weeks of therapeutic CPAP when compared to sham control.

Success in blinding to group assignment with sham-CPAP

This study evaluated the success of sham-continuous positive airway pressure (CPAP) as a placebo in a 4-week clinical trial of adults with sleep apnea. Participants (n = 23) were previously undiagnosed for obstructive sleep apnea, had no one in their household on sleep apnea therapy, and were willing to be randomly assigned to either active or sham-CPAP. Before final debriefing, participants were asked to "guess" their group assignment. When questioned, 10 of the 23 participants (44%) were incorrect in their guess of group assignment; 2 of these participants stated that their guess was "random." The active CPAP group's average usage was significantly longer when compared to participants on the sham device (293 ± 117 min/day vs. 188 ± 110 min/day, p = .046). The results suggest that participants remained blinded to group assignment and that sham-CPAP is an appropriate placebo control device. Participants' lower adherence to the sham device may be a potential problem that requires attention in the use of sham-CPAP as a placebo during clinical trials.

Improvement of EEG slowing in OSAS after CPAP treatment

OBJECTIVES

This study was done to investigate change of electroencephalography (EEG) slowing and its relationship to daytime sleepiness and cognitive functions by continuous positive airway pressure (CPAP) in patients with obstructive sleep apnea syndrome (OSAS).

METHODS

We enrolled thirteen male subjects with severe OSAS, and all the subjects were treated with CPAP for 3 months. Quantitative EEG (QEEG) and neuropsychological tests were performed before and after CPAP treatment.

RESULTS

After CPAP treatment, delta absolute power decreased in the frontal, central, parietal and temporal regions and the slowing ratio was reduced in the frontal region. The Epworth Sleepiness Scale (ESS) score was reduced after CPAP treatment. Reduction in the ESS score was correlated with a decrease in delta absolute power in the frontal region (r=0.559) and a decrease in slowing ratio in frontal, central, parietal, and temporal regions (frontal, r=0.650; other regions, r=0.603). Results of neuropsychological tests assessing memory and attention were improved after CPAP treatment.

CONCLUSIONS

EEG slowing was decreased across all cerebral regions in patients with severe OSAS after CPAP treatment accompanied by improvement of cognitive functions involving several brain areas. These findings suggest that CPAP can induce improvement of cerebral function in OSAS without regional specificity.

Continuous positive airway pressure treatment of sleepy patients with milder obstructive sleep apnea: results of the CPAP Apnea Trial North American Program (CATNAP) randomized clinical trial

RATIONALE

Twenty-eight percent of people with mild to moderate obstructive sleep apnea experience daytime sleepiness, which interferes with daily functioning. It remains unclear whether treatment with continuous positive airway pressure improves daytime function in these patients.

OBJECTIVES

To evaluate the efficacy of continuous positive airway pressure treatment to improve functional status in sleepy patients with mild and moderate obstructive sleep apnea.

METHODS

Patients with self-reported daytime sleepiness (Epworth Sleepiness Scale score >10) and an apnea-hypopnea index with 3% desaturation and from 5 to 30 events per hour were randomized to 8 weeks of active or sham continuous positive airway pressure treatment. After the 8-week intervention, participants in the sham arm received 8 weeks of active continuous positive airway pressure treatment.

MEASUREMENTS AND MAIN RESULTS

The Total score on the Functional Outcomes of Sleep Questionnaire was the primary outcome measure. The adjusted mean change in the Total score after the first 8-week intervention was 0.89 for the active group (n = 113) and -0.06 for the placebo group (n = 110) (P = 0.006). The group difference in mean change corresponded to an effect size of 0.41 (95% confidence interval, 0.14-0.67). The mean (SD) improvement in Functional Outcomes of Sleep Questionnaire Total score from the beginning to the end of the crossover phase (n = 91) was 1.73 ± 2.50 (t[90] = 6.59; P < 0.00001) with an effect size of 0.69.

CONCLUSIONS

Continuous positive airway pressure treatment improves the functional outcome of sleepy patients with mild and moderate obstructive sleep apnea.

The use of nasal dilator strips as a placebo for trials evaluating continuous positive airway pressure

OBJECTIVES

The aim of the current study was to compare the objective and subjective effects of continuous positive airway pressure to the use of nasal dilator strips in patients with acromegaly and moderate to severe obstructive sleep apnea.

METHODS

We studied 12 patients with acromegaly and moderate to severe obstructive sleep apnea (male/ females = 8/4, age = 52 ± 8 ys, body mass index = 33.5 ± 4.6 Kg/m(2), apnea-hypopnea index = 38 ± 14 events/h) who had been included in a randomized, crossover study to receive three months of treatment with continuous positive airway pressure and nasal dilator strips. All patients were evaluated at study entry and at the end of each treatment by polysomnography, and Epworth Sleepiness Scale, Pittsburgh Sleep Quality Index and treatment satisfaction questionnaires. ClinicalTrials.gov: NCT01265121

RESULTS

The apnea-hypopnea index values decreased significantly with continuous positive airway pressure treatment but did not change with the use of nasal dilator strips. All of the subjective symptoms improved with both treatments, but these improvements were significantly greater with continuous positive airway pressure than with the nasal dilator strips.

CONCLUSION

The use of nasal dilator strips had a much smaller effect on the severity of obstructive sleep apnea in patients with acromegaly and moderate to severe obstructive sleep apnea in comparison to the use of continuous positive airway pressure. Moreover, the improvement in several subjective parameters without any significant objective improvement in obstructive sleep apnea resulting from the use of nasal dilator strips is compatible with a placebo effect.

Continuous positive airway pressure reduces postprandial lipidemia in obstructive sleep apnea: a randomized, placebo-controlled crossover trial

RATIONALE

Dyslipidemia is common in Obstructive Sleep Apnea (OSA). Postprandial lipidemia (PPL) is a strong marker of cardiovascular risk. Evidence that OSA treatment improves PPL is lacking.

OBJECTIVES

To investigate the effect of continuous positive airway pressure (CPAP) treatment on postprandial lipidemia (PPL) in patients with obstructive sleep apnea (OSA) in the upper moderate or severe range.

METHODS

In this randomized, placebo-controlled crossover trial, we compared the effects of 2 months each of therapeutic and placebo CPAP on PPL.

MEASUREMENTS AND MAIN RESULTS

PPL was determined from the area under the 24-hour triglyceride concentration curve (TAG-AUC(24)) using seven blood samples drawn across both the wake and sleep periods. Secondary outcomes were the difference in other 24-hour lipid profiles. Thirty-eight eligible patients were randomly assigned to a treatment order and 29 patients completed the trial. CPAP reduced PPL compared with placebo with a mean TAG-AUC(24) difference of -357 mmol/L/d (95% confidence interval [CI], -687.3 to -26.8; P = 0.035). During both the CPAP and placebo studies, TAG levels peaked during both wakefulness (2:00 p.m.) and sleep (3:00 a.m.). Both peaks were lower during CPAP than placebo: 2:00 p.m., -0.49 mmol/L (95% CI, -0.74 to -0.24; P < 0.0005) and 3:00 a.m., -0.40 mmol/L (95% CI, -0.65 to -0.15; P = 0.002). Moreover, mean 24-hour total cholesterol was -0.19 mmol/L lower on CPAP (95% CI, -0.27 to -0.11; P < 0.00001).

CONCLUSIONS

This randomized trial demonstrated that treatment of severe OSA with CPAP improves postprandial TAG and total cholesterol levels. These effects may reduce the risk for cardiovascular events. The results imply that the association between OSA and cardiovascular disease may, in part, be caused by direct effects on dyslipidemia. Clinical trial registered with the Australian and New Zealand Clinical Trials Registry at www.anzctr.org.au (ACTRN 12605000066684).

Ethical issues in the conduct of clinical trials in obstructive sleep apnea

Scientifically rigorous clinical trials are needed to test continuous positive airway pressure's (CPAP) effect on important clinical endpoints known to be associated with obstructive sleep apnea, such as myocardial infarction, cardiac arrhythmias, stroke, mortality, seizures, and cognitive function. In this "Special Article," we review the regulatory and ethical issues that surround the design and conduct of CPAP trials, including selection of the appropriate control condition, exclusion criteria, and follow-up duration.

How treatment affects cognitive deficits in patients with sleep disorders: methodological issues and results

Sleep disorders are frequently associated with impaired performance although the type and extent of cognitive deficits varies widely between different types of sleep disorders. Treatment is expected to ameliorate these deficits. However, cognitive functioning and its change with treatment depend on numerous factors. In this chapter we discuss methodological issues, including test selection, and person-specific, task-specific and environmental factors that influence cognitive functioning. In addition, features of study design and sampling strategies are discussed. The chapter ends with a short overview of routes by which treatment may affect cognition in sleep-disordered patients.