Debby Nicoll

Effect of CPAP on insulin resistance and HbA1c in men with obstructive sleep apnoea and type 2 diabetes

Background: The effects of continuous positive airway pressure (CPAP) for obstructive sleep apnoea (OSA) on insulin resistance are not clear. Trials have found conflicting results and no appropriate control groups have been used. Methods: Forty-two men with known type 2 diabetes and newly diagnosed OSA (>10 dips/h in oxygen saturation of >4%) were randomised to receive therapeutic (n = 20) or placebo CPAP (n = 22) for 3 months. Baseline tests were performed and repeated after 3 months. The study was double blind. Results: Results are expressed as mean (SD). CPAP improved the Epworth sleepiness score significantly more in the therapeutic group than in the placebo group (−6.6 (4.5) vs −2.6 (4.9), p = 0.01). The maintenance of wakefulness test improved significantly in the therapeutic group but not in the placebo group (+10.6 (13.9) vs −4.7 (11.8) min, p = 0.001). Glycaemic control and insulin resistance did not significantly change in either the therapeutic or placebo groups: HbA1c (−0.02 (1.5) vs +0.1 (0.7), p = 0.7, 95% CI −0.6% to +0.9%), euglycaemic clamp (M/I: +1.7 (14.1) vs −5.7 (14.8), p = 0.2, 95% CI −1.8 to +0.3 l/kg/min1000), HOMA-%S (−1.5 (2.3) vs −1.1 (1.8), p = 0.2, 95% CI −0.3% to +0.08%) and adiponectin (−1.1 (1.2) vs −1.1 (1.3), p = 0.2, 95% CI −0.7 to +0.6 &mgr;g/ml). Body mass index, bioimpedance and anthropometric measurements were unchanged. Hours of CPAP use per night were 3.6 (2.8) in the treatment group and 3.3 (3.0) in the placebo group (p = 0.8). There was no correlation between CPAP use and the measures of glycaemic control or insulin resistance. Conclusion: Therapeutic CPAP does not significantly improve measures of glycaemic control or insulin resistance in men with type 2 diabetes and OSA.

Prevalence of obstructive sleep apnoea in men with type 2 diabetes

Background: A study was undertaken to establish the prevalence of obstructive sleep apnoea (OSA) in men with type 2 diabetes. Methods: Men with type 2 diabetes from local hospital and selected primary care practitioner databases received questionnaires about snoring, apnoeas, and daytime sleepiness based on the Berlin questionnaire. Selected respondents had overnight oximetry to establish whether they had OSA. Comparisons of oximetry were made with those from a previous general population study. HbA1c results were collected. Results: 1682 men were sent questionnaires, 56% of whom replied. 57% scored as “high” and 39% as “low” risk for OSA; 4% were already known to have OSA. Oximetry was performed in 240 respondents from both risk groups: 31% of the “high” and 13% of the “low” risk group had significant OSA (more than 10 >4% Sao2 dips/hour or Sao2 tracing consistent with OSA). These results were verified by detailed sleep studies. Extrapolation of the oximetry data to the questionnaire respondent population suggests that 23% had OSA. Comparison of the oximetry results with men from a previous general population study (using only more than 10 >4% Sao2 dips/hour to define OSA) showed the prevalence of OSA is significantly higher in this diabetes population (17% v 6%, p<0.001). Multiple linear regression revealed BMI and diabetes as significant independent predictors of OSA. Following correction for BMI (which explained 13% of the variance in OSA), diabetes explained a further 8% of the variance (p<0.001). There was a low correlation between OSA severity and HbA1c in the subgroup recruited from the hospital database (r = 0.2, p = 0.006) which remained significant after allowing for obesity (p = 0.03). Conclusions: OSA is highly prevalent in men with type 2 diabetes; most are undiagnosed. Diabetes itself may be a significant independent contributor to the risk of OSA.

Endothelial Function and Arterial Stiffness in Minimally Symptomatic Obstructive Sleep Apnea

RATIONALE Moderate-severe obstructive sleep apnea (OSA) is associated with endothelial dysfunction, increased arterial stiffness, and hypertension. It is not known whether minimally symptomatic OSA is also associated with impaired vascular function. OBJECTIVES To determine whether minimally symptomatic OSA is associated with impaired vascular function. METHODS In 64 patients (7 females) with minimally symptomatic OSA (oxygen desaturation index, 23.1 [SD, 15.6]; Epworth Sleepiness Scale score, 8 [SD, 3.8]), and 15 matched control subjects without OSA, endothelial function was assessed by ultrasonographic measurement of flow-mediated dilatation, and by applanation tonometry-derived pulse wave analysis (forearm ischemia and salbutamol-induced changes in augmentation index, AI(x)). Arterial stiffness was assessed by AI(x) and ambulatory blood pressure (ABP) was measured over 1 week. MEASUREMENTS AND MAIN RESULTS In patients with OSA, flow-mediated dilatation was significantly lower than in control subjects (5.0% [SD, 2.7%] and 7.5% [SD, 3.3%], respectively; P = 0.003). AI(x) was significantly higher in the OSA group compared with the control group (26.0% [interquartile range (IQR), 19.0-29.5%] and 21.0% [IQR, 8.0-27.0%], respectively; P = 0.04). Change in AI(x) after both forearm ischemia and salbutamol was significantly smaller in patients with OSA (-2.0% [IQR, -5.0 to +4.0%] and -3.0% [IQR, -7.0 to 0.0%], respectively), than in control subjects (-6.0% [IQR, -8.0 to -5.0%] and -7.0% [IQR, -10.0 to -3.0%]; P = 0.005 and P = 0.04, respectively). ABP was similar (97.6 mm Hg [SD, 7.9 mm Hg] and 94.8 mm Hg [SD, 7.4 mm Hg], OSA and control groups, respectively; P = 0.21). CONCLUSIONS In patients with minimally symptomatic OSA, diverse properties of endothelial function are impaired and arterial stiffness is increased. Although this was not associated with a significantly increased ABP, the findings suggest that patients with minimally symptomatic OSA are at increased cardiovascular risk.

Continuous positive airway pressure improves sleepiness but not calculated vascular risk in patients with minimally symptomatic obstructive sleep apnoea: the MOSAIC randomised controlled trial

Background Continuous positive airway pressure (CPAP) for symptomatic obstructive sleep apnoea (OSA) improves sleepiness and reduces vascular risk, but such treatment for the more prevalent, minimally symptomatic disease is contentious. Methods This multicentre, randomised controlled, parallel, hospital-based trial across the UK and Canada, recruited 391 patients with confirmed OSA (oxygen desaturation index >7.5/h) but insufficient symptoms to warrant CPAP therapy. Patients were randomised to 6 months of auto-adjusting CPAP therapy, or standard care. Coprimary endpoints were change in Epworth Sleepiness Score (ESS) and predicted 5-year mortality using a cardiovascular risk score (components: age, sex, height, systolic blood pressure, smoking, diabetes, cholesterol, creatinine, left ventricular hypertrophy, previous myocardial infarction or stroke). Secondary endpoints included some of the individual components of the vascular risk score, objectively measured sleepiness and self-assessed health status. Results Of 391 patients randomised, 14 withdrew, 347 attended for their follow-up visit at 6 months within the predefined time window, of which 341 had complete ESS data (baseline mean 8.0, SD 4.3) and 310 had complete risk score data. 22% of patients in the CPAP group reported stopping treatment and overall median CPAP use was 2 : 39 h per night. CPAP significantly improved subjective daytime sleepiness (adjusted treatment effect on ESS −2.0 (95% CI −2.6 to −1.4), p<0.0001), objectively measured sleepiness and self-assessed health status. CPAP did not improve the 5-year calculated vascular risk or any of its components. Conclusions In patients with minimally symptomatic OSA, CPAP can reduce subjective and objective daytime sleepiness, and improve self-assessed health status, but does not appear to improve calculated vascular risk.

The effect of continuous positive airway pressure treatment on physical activity in patients with obstructive sleep apnoea: A randomised controlled trial.

BACKGROUND Continuous positive airway pressure (CPAP) improves daytime sleepiness in patients with obstructive sleep apnoea (OSA). The effect of CPAP on physical activity is unclear. We hypothesized that activity would increase after CPAP treatment. METHODS A double blind, parallel, randomised, controlled trial using therapeutic and placebo CPAP was performed in men with newly diagnosed OSA (more than 10>4% SaO(2) dips/hour and Epworth Sleepiness Score [ESS] 9). Activity was measured by wrist actigraphy before and after three months of CPAP therapy. RESULTS Thirty-six men completed 1 week of continuous actigraphy before and after therapeutic CPAP (n=16) or placebo CPAP (n=20). The two groups were well-matched at baseline, with no significant differences in mean age, body mass index, ESS and SaO(2) dips/hour. Mean (SD) ESS and modified maintenance of wakefulness test (OSLER) improved significantly after CPAP. ESS change in the therapeutic group was -6.1 (4.4), compared to placebo, -2.8 (5.0); difference between groups p=0.04; OSLER (minutes), therapeutic +10.4 (14.4), placebo -5.0 (12.0), p=0.003. There was no significant difference between groups in mean hourly activity levels for the seven days at baseline; activity levels did not significantly change in either group after CPAP [daytime activity (arbitrary units): therapeutic -13.9 (93.1) vs. placebo +8.3 (62.9), p=0.4]. There was no correlation between change in activity and CPAP use. CONCLUSION Activity does not increase after CPAP in men with OSA, despite improvements in daytime sleepiness. The reasons for this are not clear, but may be due to longstanding, habitual patterns of activity.

CPAP Improves Endothelial Function in Patients With Minimally Symptomatic OSA : Results From a Subset Study of the MOSAIC Trial

BACKGROUND Minimally symptomatic OSA is a highly prevalent disorder, and the effects of CPAP on vascular function in these patients are unknown. This trial aimed to investigate whether CPAP improves vascular function in minimally symptomatic OSA. METHODS In two centers taking part in the MOSAIC (Multicentre Obstructive Sleep Apnoea Interventional Cardiovascular) trial, 253 patients with minimally symptomatic OSA were randomized to 6 months of CPAP or standard care. Two hundred eight patients attended their follow-up visit within the predefined time window and had complete measurements of arterial stiffness (augmentation index [AIx]), and 64 patients had endothelial function measurements by brachial artery flow-mediated dilatation (FMD). Multivariable analyses adjusting for baseline measurements and minimization factors were performed to assess the effect of CPAP treatment on FMD (% dilatation) and AIx (% augmentation) compared with standard care. RESULTS The mean ± SD baseline oxygen desaturation index and Epworth Sleepiness Score (ESS) of the 208 patients (age 58 ± 7.3 years, 31 women) were 13.7 ± 12.8 events/h and 8.3 ± 4.2, respectively. There was no CPAP treatment effect on arterial stiffness (AIx, -1.4%; 95% CI, -3.6 to +0.9%; P = .23), but CPAP improved endothelial function (FMD, +2.1%; 95% CI, +1.0 to +3.2%; P < .0001). CPAP reduced daytime sleepiness (ESS, -2.2; 95% CI, -3.0 to -1.5; P < .0001) compared with standard care. There was a larger improvement in FMD in patients using CPAP for > 4 h/night than those who used it less (P = .013). CONCLUSIONS CPAP improves endothelial function, but not arterial stiffness, in minimally symptomatic OSA. Thus, minimally symptomatic OSA may be a cardiovascular risk factor. TRIAL REGISTRY ISRCTN Register; No.: ISRCTN 34164388; URL: http://isrctn.org.

Circulating cell-derived microparticles in patients with minimally symptomatic obstructive sleep apnoea.

Moderate–severe obstructive sleep apnoea (OSA) has been associated with several pro-atherogenic mechanisms and increased cardiovascular risk, but it is not known if minimally symptomatic OSA has similar effects. Circulating cell-derived microparticles have been shown to have pro-inflammatory, pro-coagulant and endothelial function-impairing effects, as well as to predict subclinical atherosclerosis and cardiovascular risk. In 57 patients with minimally symptomatic OSA, and 15 closely matched control subjects without OSA, AnnexinV-positive, platelet-, leukocyte- and endothelial cell-derived microparticles were measured by flow cytometry. In patients with OSA, median (interquartile range) levels of AnnexinV-positive microparticles were significantly elevated compared with control subjects: 2,586 (1,566–3,964) μL−1 versus 1,206 (474–2,501) μL−1, respectively. Levels of platelet-derived and leukocyte-derived microparticles were also significantly higher in patients with OSA (2,267 (1,102–3,592) μL−1 and 20 (14–31) μL−1, respectively) compared with control subjects (925 (328–2,068) μL−1 and 15 (5–23) μL−1, respectively). Endothelial cell-derived microparticle levels were similar in patients with OSA compared with control subjects (13 (8–25) μL−1 versus 11 (6–17) μL−1). In patients with minimally symptomatic obstructive sleep apnoea, levels of AnnexinV-positive, platelet- and leukocyte-derived microparticles are elevated when compared with closely matched control subjects without obstructive sleep apnoea. These findings suggest that these patients may be at increased cardiovascular risk, despite being minimally symptomatic.

Original ResearchSleep DisordersCPAP Improves Endothelial Function in Patients With Minimally Symptomatic OSA: Results From a Subset Study of the MOSAIC Trial

BACKGROUND Minimally symptomatic OSA is a highly prevalent disorder, and the effects of CPAP on vascular function in these patients are unknown. This trial aimed to investigate whether CPAP improves vascular function in minimally symptomatic OSA. METHODS In two centers taking part in the MOSAIC (Multicentre Obstructive Sleep Apnoea Interventional Cardiovascular) trial, 253 patients with minimally symptomatic OSA were randomized to 6 months of CPAP or standard care. Two hundred eight patients attended their follow-up visit within the predefined time window and had complete measurements of arterial stiffness (augmentation index [AIx]), and 64 patients had endothelial function measurements by brachial artery flow-mediated dilatation (FMD). Multivariable analyses adjusting for baseline measurements and minimization factors were performed to assess the effect of CPAP treatment on FMD (% dilatation) and AIx (% augmentation) compared with standard care. RESULTS The mean ± SD baseline oxygen desaturation index and Epworth Sleepiness Score (ESS) of the 208 patients (age 58 ± 7.3 years, 31 women) were 13.7 ± 12.8 events/h and 8.3 ± 4.2, respectively. There was no CPAP treatment effect on arterial stiffness (AIx, -1.4%; 95% CI, -3.6 to +0.9%; P = .23), but CPAP improved endothelial function (FMD, +2.1%; 95% CI, +1.0 to +3.2%; P < .0001). CPAP reduced daytime sleepiness (ESS, -2.2; 95% CI, -3.0 to -1.5; P < .0001) compared with standard care. There was a larger improvement in FMD in patients using CPAP for > 4 h/night than those who used it less (P = .013). CONCLUSIONS CPAP improves endothelial function, but not arterial stiffness, in minimally symptomatic OSA. Thus, minimally symptomatic OSA may be a cardiovascular risk factor. TRIAL REGISTRY ISRCTN Register; No.: ISRCTN 34164388; URL: http://isrctn.org.

Markers of inflammation: data from the MOSAIC randomised trial of CPAP for minimally symptomatic OSA

ABSTRACT The Multi-centre Obstructive Sleep Apnoea Interventional Cardiovascular (MOSAIC) trial compared 6 months of CPAP therapy, versus no CPAP, in 391 patients with minimally symptomatic obstructive sleep apnoea (OSA). We now report some exploratory outcomes, markers of systemic inflammation (interleukin 6 (IL-6), IL-10, C reactive protein, tumour necrosis factor). We found no consistent changes (all p values >0.13). Trial registration number: ISRCTN 34164388.

Effect of CPAP on Cardiac Function in Minimally Symptomatic Patients with OSA: Results from a Subset of the MOSAIC Randomized Trial

STUDY OBJECTIVES Minimally symptomatic obstructive sleep apnea (OSA) is highly prevalent, and the effects of continuous positive airway pressure (CPAP) on myocardial function in these patients are unknown. The MOSAIC randomized, controlled trial of CPAP for minimally symptomatic OSA assessed the effect of CPAP on myocardial function in a subset of patients. METHODS Two centers taking part in the MOSAIC trial randomized 238 patients in parallel to 6 months of CPAP (120) or standard care (118). Of these, 168 patients had echocardiograms, and 68 patients had a cardiac magnetic resonance scan (CMR). A larger group (314) from 4 centers had brain natriuretic peptide (BNP) measured. RESULTS Mean (SD) baseline oxygen desaturation index (ODI) and Epworth sleepiness score (ESS) were 13.5 (13.2), and 8.4 (4.0), respectively. CPAP significantly reduced ESS and ODI. Baseline LV ejection fraction (LVEF) was well preserved (60.4%). CPAP had no significant effect on echo-derived left atrial (LA) area (-1.0 cm2, 95% CI -2.6 to +0.6, p = 0.23) or early to late left ventricular filling velocity (E/A) ratio (-0.01, 95% CI -0.07 to +0.05, p = 0.79). There was a small change in echo-derived LV end diastolic volume (EDV) with CPAP (-5.9 mL, 95% CI -10.6 to -1.2, p = 0.015). No significant changes were detected by CMR on LV mass index (+1.1 g/m(2), 95% CI -5.9 to +8.0, p = 0.76) or LVEF (+0.8%, 95% CI -1.2 to +2.8, p = 0.41). CPAP did not affect BNP levels (p = 0.16). CONCLUSIONS Six months of CPAP therapy does not change cardiac functional or structural parameters measured by echocardiogram or CMR in patients with minimally symptomatic mild-to-moderate OSA. CLINICAL TRIAL REGISTRATION ISRCTN 34164388 (http://isrctn.org).