Maintenance of Wakefulness Test scores and driving performance in sleep disorder patients and controls

Objective

Sleepiness at the wheel is a risk factor for traffic accidents. Past studies have demonstrated the validity of the Maintenance of Wakefulness Test (MWT) scores as a predictor of driving impairment in untreated patients with obstructive sleep apnea syndrome (OSAS), but there is limited information on the validity of the maintenance of wakefulness test by MWT in predicting driving impairment in patients with hypersomnias of central origin (narcolepsy or idiopathic hypersomnia). The aim of this study was to compare the MWT scores with driving performance in sleep disorder patients and controls.

Methods

19 patients suffering from hypersomnias of central origin (9 narcoleptics and 10 idiopathic hypersomnia), 17 OSAS patients and 14 healthy controls performed a MWT (4 × 40-minute trials) and a 40-minute driving session on a real car driving simulator. Participants were divided into 4 groups defined by their MWT sleep latency scores. The groups were pathological (sleep latency 0–19 min), intermediate (20–33 min), alert (34–40 min) and control (> 34 min). The main driving performance outcome was the number of inappropriate line crossings (ILCs) during the 40 minute drive test.

Results

Patients with pathological MWT sleep latency scores (0–19 min) displayed statistically significantly more ILC than patients from the intermediate, alert and control groups (F (3, 46) = 7.47, p < 0.001).

Interpretation

Pathological sleep latencies on the MWT predicted driving impairment in patients suffering from hypersomnias of central origin as well as in OSAS patients. MWT is an objective measure of daytime sleepiness that appears to be useful in estimating the driving performance in sleepy patients.     

The Maintenance of Wakefulness Test and driving simulator performance

STUDY OBJECTIVES: It has been suggested that the Maintenance of Wakefulness Test (MWT) may be clinically useful to assess fitness to drive, yet little is known about the actual relationship between sleep latency and driving performance. This study examined the ability of 2 MWT trials to predict driving-simulator performance in healthy individuals. DESIGN: Experimental. SETTING: NA. PATIENTS OR PARTICIPANTS: Twenty healthy volunteers (mean age 22.8 years; 9 men). INTERVENTIONS: NA. MEASUREMENTS AND RESULTS: The MWT and driving-simulator performance were examined under 2 conditions-partial sleep deprivation and a combination of partial sleep deprivation and alcohol consumption. Each subject was studied a week apart, with the order randomly assigned. Subjects completed a nighttime 70-minute AusEd driving simulation task and two 40-minute MWT trials, 1 before (MWT1) and 1 after (MWT2) the driving task. In the sleep-deprived condition, the MWT1 sleep latency was inversely correlated with braking reaction time. During the partial sleep deprivation and alcohol condition, the number of microsleeps during the driving task, steering deviation, braking reaction time, and crashes all negatively correlated with the MWT1 sleep latency. Additionally, construction of a receiver-operator characteristic curve revealed that MWT1 sleep latency in the partial sleep deprivation plus alcohol condition significantly discriminated subjects who had a crash from those who did not. CONCLUSIONS: These results indicate that sleep latency on the MWT is a reasonable predictor of driving simulator performance in sleepy, alcohol-impaired, normal subjects. Further research is needed to examine the relationship between daytime MWT results and driving simulator performance in sleepy patients (eg, those with obstructive sleep apnea) and in experimentally sleep-deprived normal subjects.     

The effect of in-laboratory polysomnography on sleep and objective daytime sleepiness

MSLT guidelines recommend performing MSLTs following polysomnography (PSG) to document the preceding night's sleep. We tested the hypothesis that patients are objectively sleepier after in-laboratory full diagnostic PSG than after a sleep recording at home. Sixteen patients with the sleep apnea/hypopnea syndrome (SAHS; AHI 35+/-SD 28 per hour slept) were recruited into a randomized crossover study. To monitor sleep with minimal disruption at home, only sleep was recorded on 2 consecutive nights, the first for acclimatization. The laboratory limb followed standard PSG. Both study nights were followed next day by MSLT and MWT. There were no differences in MSLT (12.0 SD 5.1 home, 11.6+/-4.7 min laboratory; p=0.7), MWT (32.7+/-8.7, 31.6+/-9.3 min; p=0.6) or total sleep time (362+/-53, 343+/-51 min; p=0.15) between home and laboratory limbs. However, on the home night, fewer microarousals (31+/-14, 54+/-25/hr slept; p<0.0001) and less % wake (15+/-10, 24+/-11; p=0.006) were found. On the home study night, patients had greater % REM sleep, slow-wave sleep and sleep efficiency (all p<0.009). This study does not support the hypothesis that patients are sleepier after laboratory PSG compared to home study night. However, the improved sleep at home raises the question whether laboratory-based polysomnography is always required prior to MSLT/MWT testing or whether less obtrusive monitoring of sleep duration at home would sometimes suffice.     

Factors associated with maintenance of wakefulness test mean sleep latency in patients with mild to moderate obstructive sleep apnoea and normal subjects

This study investigated the possible factors related to the Maintenance of Wakefulness Test (MWT) mean sleep latency. A second analysis explored the characteristics of subjects who had discrepant Epworth Sleepiness Scale (ESS) and MWT scores. A total of 151 subjects (110 mild to moderate obstructive sleep apnoea (OSA) patients and 41 control subjects) were recruited for the study. The subjects completed an overnight Polysomnography (PSG), MWT, cognitive, performance and vigilance tasks and answered self-report questionnaires on mood and sleepiness. A forward stepwise multiple regression was performed on MWT mean sleep latency. The predictor variables age (r = 0.28), subjective sleep history for 1 week prior to MWT (sleep diary; r = 0.19) and number of >4% SaO2 Dips during the PSG (r = -0.21) best explained the MWT results, but only accounted for 12.8% of the variance in the test. It was found that 33% of subjects had discrepant ESS and MWT scores. A new variable was created to analyse these subjects (MWT/ESS discrepancy score; MED). A forward stepwise multiple regression analysis found that depression, performance errors and sleep disordered breathing explained 13.4% of the variance in MED scores. The MWT is a complex behavioural test whose scores do not seem to have a very robust relationship with potential predictors and co-correlates. Further comprehensive study is needed if the test is to be used in a diagnostically meaningful way.     

Daytime Sleepiness and Driving Performance in Patients with Obstructive Sleep Apnea: Comparison of the MSLT,the MWT,and a Simulated Driving Task

Study Objectives:

To test the reliability of a driving-simulation test for the objective measurement of daytime alertness compared with the Multiple Sleep Latency Test (MSLT) and with the Maintenance of Wakefulness Test (MWT), and to test the ability to drive safely, in comparison with on-road history, in the clinical setting of untreated severe obstructive sleep apnea.

Design:

N/A.

Setting:

Sleep laboratory.

Patients or Participants:

Twenty-four patients with severe obstructive sleep apnea and reported daytime sleepiness varying in severity (as measured by the Epworth Sleepiness Scale).

Interventions:

N/A.

Measurements and Results:

Patients underwent MSLT and MWT coupled with 4 sessions of driving-simulation test on 2 different days randomly distributed 1 week apart. Simulated-driving performance (in terms of lane-position variability and crash occurrence) was correlated with sleep latency on the MSLT and more significantly on the MWT, showing a predictive validity toward the detection of sleepy versus alert patients with obstructive sleep apnea. In addition, patients reporting excessive daytime sleepiness or a history of car crashes showed poorer performances on the driving simulator.

Conclusions:

A simulated driving test is a suitable tool for objective measurement of daytime alertness in patients with obstructive sleep apnea. Further studies are needed to clarify the association between simulated-driving performance and on-road crash risk of patients with sleep disordered breathing.

Citation:

Pizza F; Contardi S; Mondini S; Trentin L; Cirignotta F. Daytime sleepiness and driving performance in patients with obstructive sleep apnea: comparison of the MSLT, the MWT, and a simulated driving task. SLEEP 2009;32(3):382-391.     

Microsleep as a marker of sleepiness in obstructive sleep apnea patients

We hypothesized that: (a) the presence of microsleep (MS) during a Maintenance Wakefulness Test (MWT) trial may represent a reliable marker of sleepiness in obstructive sleep apnea (OSA) patients; (b) the number of MSs will be higher in sleepy versus non‐sleepy patients with a borderline MWT mean sleep latency; and (c) scoring MS during MWT analysis may help physicians to recognize patients with a higher degree of sleepiness. We analysed the MWT data of 112 treatment‐naïve OSA patients: 20 with short sleep latency (SL, sleep latency <12.8 min), 43 with borderline latency (BL, sleep latency between 12.8 and 32.6 min) and 49 with normal latency (NL, sleep latency >32.6 min). Microsleep was identified in all SL, in 42 BL and in 18 NL patients, with a median latency of 5.6 min. Accordingly, patients were classified into two subgroups: group A (n = 43) with microsleep latency <5.6 min and group B (n = 69) with microsleep latency >5.6 min when present. The mean sleep latency in the MWT was 14.5 ± 7.5 min in group A and 34.6 ± 7.4 min in group B (p < 0.0001). The number of microsleep episodes during each MWT trial was higher in group A than in group B. Sleep latency survival curves demonstrated different patterns of sleep latency in these groups (log‐rank test <0.0001). This finding was confirmed in a Cox proportional hazard analysis: the presence of a mean MS latency <5.6 min is associated with an increasing risk of falling asleep during the MWT (RR, 1.93; 95 CI 1.04–3.6; p = 0.03). We conclude that the detection of microsleep may help in discriminating OSA patients with and without daytime vigilance impairment.     

Correlation between the severity of obstructive sleep apnea and heart rate variability indices

The risk of cardiovascular disease is known to be increased in obstructive sleep apnea syndrome (OSAS). Its mechanism can be explained by the observation that the sympathetic tone increases due to repetitive apneas accompanied by hypoxias and arousals during sleep. Heart rate variability (HRV) representing cardiac autonomic function is mediated by respiratory sinus arrhythmia, baroreflex-related fluctuation, and thermoregulation-related fluctuation. We evaluated the heart rate variability of OSAS patients during night to assess their relationship with the severity of the symptoms. We studied overnight polysomnographies of 59 male untreated OSAS patients with moderate to severe symptoms (mean age 45.4+/- 11.7 yr, apnea-hypopnea index [AHI]=43.2+/-23.4 events per hour, and AHI >15). Moderate (mean age 47.1+/-9.4 yr, AHI=15-30, n=22) and severe (mean age 44.5 +/-12.9 yr, AHI >30, n=37) OSAS patients were compared for the indices derived from time and frequency domain analysis of HRV, AHI, oxygen desaturation event index (ODI), arousal index (ArI), and sleep parameters. As a result, the severe OSAS group showed higher mean powers of total frequency (TF) (p=0.012), very low frequency (VLF) (p= 0.038), and low frequency (LF) (p=0.002) than the moderate OSAS group. The LF/HF ratio (p=0.005) was higher in the severe group compared to that of the moderate group. On the time domain analysis, the HRV triangular index (p=0.026) of severe OSAS group was significantly higher. AHI was correlated best with the LF/HF ratio (r(p))=0.610, p<0.001) of all the HRV indices. According to the results, the frequency domain indices tended to reveal the difference between the groups better than time domain indices. Especially the LF/HF ratio was thought to be the most useful parameter to estimate the degree of AHI in OSAS patients.     

Blink duration as an indicator of driver sleepiness in professional bus drivers.

This study focused on eyeblink duration as a measure of sleepiness in on-road driving and on the driving performance of professional bus drivers with polysomnographically confirmed mild obstructive Sleep Apnea Syndrome (OSAS). Ten bus drivers with OSAS and their matched controls participated in the study. The Maintenance of Wakefulness Test (MWT) and a monotonous on-road driving task were completed. Eyeblink duration and frequency and speed control were measured while driving. Lane-keeping was evaluated by the supervisor in the car. Subsequent to these tasks, drivers with OSAS received continuous positive airway pressure treatment (nasal CPAP). After nine weeks of treatment, the tasks were repeated. Prior to treatment the average blink duration in the driving task was significantly longer and sleep latency in the MWT was significantly shorter for bus drivers with OSAS than for controls (mean blink duration 82.3 ms; 51.9 ms and mean sleep latency 23.2 min; 35.4 min), indicating increased daytime sleepiness. Subsequent to treatment both measures in drivers with OSAS decreased to the level of the controls. Treatment effects in MWT and blink duration in on-road driving also correlated significantly. No significant differences between the groups appeared in average blink frequency or driving performance in terms of maintenance of speed. No significant lane drifting appeared either. These results support earlier findings on blink duration as an indicator of increased sleepiness and have important implications for those involved in the transport technological industry. The findings also suggest that nasal CPAP treatment is effective in reducing excessive daytime sleepiness.     

N-terminal pro-brain natriuretic peptide for detection of cardiovascular stress in patients with obstructive sleep apnea syndrome

Patients with obstructive sleep apnea syndrome (OSAS) have an elevated incidence of cardiovascular events that may be related to an increased ventricular load and hypoxemia caused by apneas and hypopneas. N-terminal pro-brain natriuretic peptide (NTproBNP) appears to be an excellent marker of myocardial stretch and could serve as an indicator of subclinical cardiac stress, thereby identifying a patient population at risk for cardiac effects from OSAS. Adult patients presenting with suspected OSAS and scheduled for nocturnal polysomnography were recruited. Patients with heart or renal failure or severe lung disease were excluded. NTproBNP was measured the evening before and the morning after sleep. Blood pressure (BP) was monitored intermittently throughout the night. Fifteen male and 15 female subjects with a mean +/- SD body mass index of 38.2 +/- 9.8 were studied. Mean Apnea-Hypopnea Index (AHI) was 38.4 +/- 26, with 17 subjects having severe OSAS (AHI > 30). No subject had a significant rise in BP. NTproBNP values overnight decreased in 19 patients and rose in 11 (mean change 3.8 +/- 33 pg mL(-1)), but only one patient had an abnormal morning value. Three patients had an abnormal NTproBNP value prior to sleep, but their levels decreased with sleep. No correlations were detected between the evening baseline or postsleep NTproBNP levels and OSAS. Monitoring pre- and postsleep NTproBNP levels revealed no association with the occurrence or degree of OSAS, making it unlikely that NTproBNP could serve as a marker of cardiac stress in OSAS patients with stable BP and without overt heart failure.     

Sleep apnea in acute cerebrovascular diseases: final report on 128 patients

Although obstructive sleep apnea (OSA) appears to be a cardiovascular risk factor, its frequency in patients with transient ischemic attack (TIA) and stroke remains poorly known. We prospectively studied 128 patients (mean +/- SD age = 59 +/- 15 years) with stroke (n = 75) or TIA (n = 53). Assessment included body mass index (BMI); history of snoring and daytime sleepiness; cardiovascular risk factors and diseases; and severity of stroke (Scandinavian Stroke Scale = SSS). Polysomnography (PSG) was obtained in 80 subjects (group 1), a mean of 9 days (range, 1-71 days) after TIA or stroke. In 48 subjects (group 2), PSG was not available, refused, or inadequate. Groups 1 and 2 were similar with the exception of gender distribution. Clinical and PSG data were compared to those of 25 healthy controls matched for age, gender, and BMI. An apnea-hypopnea index (AHI) > 10 was found in 62.5% of subjects and 12.5% of controls. Between patients and controls there was a significant difference in AHI (mean [range]: 28 (0-140) vs 5 (0-24), p < 0.001), maximal apnea duration (mean + SD: 37 +/- 23 vs 23 +/- 13 seconds, p = 0.009), and minimal oxygen saturation (mean + SD: 82 +/- 10% vs 90 +/- 5%, p < 0.001). Conversely, frequency and severity of OSA were similar in stroke and TIA subjects. Multiple regression analysis identified age, BMI, diabetes, and SSS as independent predictors of AHI. Sleep apnea has a high frequency in patients with TIA and stroke, particularly in older patients with high BMI, diabetes, and severe stroke. These results may have implications for prevention, acute treatment, and rehabilitation of patients with acute cerebrovascular diseases.     

Polysomnographic, performance, and personality differences of sleepy and alert normals

The nocturnal sleep, performance, and personality of healthy, asymptomatic, normal young men, 18 who had unusually short sleep latencies on the Multiple Sleep Latency Test (average latency, less than or equal to 6 min) and 20 with unusually long latencies (average latency, greater than or equal to 16 min) were compared. On the nocturnal sleep recording, sleepy subjects had a shorter sleep latency, less waking time, and overall greater sleep efficiency than alert subjects. During the day, sleepy subjects performed more poorly than alert subjects on divided attention and vigilance performance tasks. The sleepy and alert subjects did not differ appreciably on the Minnesota Multiphasic Personality Inventory and Jenkins Activity measures of personality. On the Institute of Personality and Ability Testing Anxiety Scale, the sleepy subjects showed higher levels of anxiety than the alert subjects. The data were interpreted as indicating that the sleepy subjects had a sleep debt due to chronic sleep restriction.     

Willingness to pay for polysomnography in children with obstructive sleep apnea syndrome: a cost-benefit analysis

OBJECTIVES: To analyze willingness to pay (WTP) for polysomnography (PSG) among parents of children with obstructive sleep apnea syndrome (OSAS). To analyze the cost-benefit of PSG in a collectively funded healthcare system. SETTING: University-affiliated sleep laboratory. SUBJECTS: Parents of 158 boys and 94 girls, who had a mean age of 6.0 +/- 3.9 years. The telephone survey, using a contingent valuation approach, was conducted with 3 groups of parents: those whose children were scheduled for PSG (n = 83), whose children were had had PSG within the previous 6 months (n = 77), and whose children had had PSG and adenotonsillectomy in the previous 6 months (n = 92). RESULTS: Two hundred and fifty-two parents (92% compliance rate), 75% of whom were mothers, responded to the WTP interview. Multivariate analysis revealed that the independent variables influencing WTP were bid (OR = 0.745, P < .001), age times bid (OR = 0.835, P < .05), and affected health status (OR = 3.5, P < .001). The median WTP value for PSG studies of children with OSAS following adenotonsillectomy was dollars 762 plus the savings of dollars 60 to the health care system-subtracting the cost of the dollars 250 PSG study resulted in a monetary benefit of dollars 572 per diagnosis. CONCLUSIONS: We conclude that PSG diagnosis for children with OSAS is beneficial. Decision makers and sleep specialists can use WTP to prioritize allocation of resources to increase the availability of PSG studies for children.     

阻塞性睡眠呼吸暂停综合征患者血清IL-6、TNF-α测定的临床意义

目的:探讨阻塞性睡眠呼吸暂停综合征(OSAS)患者血清IL-6、TNF-α水平测定的临床意义。方法:68例OSAS患者分为轻度组(36例)和中、重度组(32例),同时选取健康对照者30例,采用酶联免疫吸附法(ELISA)测定其血清IL-6、TNF-α水平,同时检测睡眠呼吸暂停低通气指数(AHI)及夜间最低血氧饱和度(SaO2),并进行相关性分析。32例中、重度OSAS患者经鼻持续正压通气(nCPAP)治疗,于治疗前及治疗后监测AHI、SaO2、IL-6和TNF-α水平。结果:OSAS患者AHI和血清IL-6、TNF-α水平显著高于对照组(P<0.01),平均SaO2和最低SaO2与对照组相比明显降低(P<0.01)。中、重度OSAS患者经nCPAP后AHI和最低SaO2明显改善,血清IL-6和TNF-α水平均较治疗前明显降低(P<0.01)。OSAS患者血清IL-6、TNF-α水平分别与AHI呈正相关(r=0.75,r=0.82,P<0.01);与SaO2呈负相关(r=-0.65、r=-0.74,P<0.01)。结论:血清IL-6、TNF-α参与了OSAS的发病,而且与病情严重程度密切相关。     

Efficacy and cost of home-initiated auto-nCPAP versus conventional nCPAP

STUDY OBJECTIVES: To compare in a multicenter prospective study the efficacy and cost of conventional nasal continuous positive airway pressure (nCPAP) initiated at the sleep laboratory versus auto-nCPAP initiated at home. DESIGN: Patients with severe obstructive sleep apnea syndrome (OSAS) were randomized to treatment with either the REM+ auto device in constant mode at the effective pressure determined by titration at the sleep laboratory (n=17) or the REM+ auto device in automatic mode initiated at the patients home by a nurse (n=18). After 2 months, the efficacy and cost of nCPAP therapy and the time from diagnosis to nCPAP were evaluated. All values are reported as means +/- SD. PATIENTS: Thirty-five subjects with newly diagnosed OSAS (8 women and 27 men, mean age: 54.3 +/- 10.6 years, apnea-hypopnea index (AHI) 58.1 +/- 14.0 h(-1)). INTERVENTIONS: N/A MEASUREMENTS AND RESULTS: Both treatments were used properly and induced similar decreases in the AHI (7.6 +/- 6.9 vs. 10.4 +/ -12.5 h(-1) for auto-nCPAP and conventional nCPAP, respectively; NS) and Epworth Sleepiness score (from 15.5 +/- 4.7 to 7.5 +/- 3.4 vs. 14.7 +/- 3.9 to 7.6 +/- 3.4 for auto-nCPAP and conventional nCPAP, respectively; NS). With auto-nCPAP initiated at home, the time from diagnosis to final adjustment of nCPAP was shorter (16.3 +/- 5.0 vs. 47.2 +/- 46.5 days with conventional nCPAP, P < 0.02) and the cost was lower (1,263 +/- 352 vs. 1720+/-455 E, respectively; P < 0.05). CONCLUSIONS: Treatment of OSAS with auto-nCPAP initiated at home is effective and reliable and reduces the time from diagnosis to therapy and the cost of treatment.     

Utility of actigraphy in the diagnosis of obstructive sleep apnea

STUDY OBJECTIVES: To determine whether adding actimetry to simplified polygraphy (respiratory-parameter monitoring without neurophysiologic variable recording) improves apnea-hypopnea index (AHI) evaluation as compared to simplified polygraphy alone. DESIGN: Comparison of AHI values obtained by all-night polysomnography and by simplified polygraphy with and without actimetry. SETTING: A teaching-hospital sleep laboratory in Garches, France. PATIENTS: 20 adults with suspected obstructive sleep apnea syndrome (OSAS). MEASUREMENTS AND RESULTS: Data were analyzed by two scorers working independently. AHI was calculated as the number of apneas and hypopneas per hour of sleep time (polysomnography: AHI-pg), per hour of time in bed (simplified polygraphy: AHI-tib), and per hour of actimetry-estimated total sleep time (AHI-act). AHI-pg showed that 12 patients had OSAS (AHI>10), which was severe (AHI > or =30) in eight. AHI-act was more closely correlated to AHI-pg (r=0.976) than was AHI-tib (r=0.940). According to the Bland and Altman method, AHI-tib underestimated the AHI in two patients and AHI-act overestimated the AHI in one patient. For the diagnosis of severe OSAS, sensitivity and negative predictive value were 50% and 75% with AHI-tib as compared to 88% and 92.5% with AHI-act. CONCLUSIONS: Actimetry, when added to simplified polygraphy, may assist in the diagnosis of OSAS.     

78例睡眠呼吸暂停综合征患者的睡眠特征及其与夜间低氧血症的关系

目的 :了解SAS患者的睡眠特征及其与夜间低氧血症的关系。方法 :采用PSG对 78例SAS患者和 30例正常对照者进行整夜睡眠监测 ,比较两组间的睡眠特征。并对不同严重程度的夜间低氧血症SAS患者进行睡眠变量比较 ,分析二者的关系。结果 :与正常对照者相比 ,SAS患者夜间睡眠结构紊乱 ,主要为深睡眠减少、浅睡眠相对增加、REM睡眠减少、觉醒增加、睡眠潜伏期缩短、呼吸暂停或低通气次数增加、动脉血氧饱和显著下降 (P <0 .0 5 )。SAS患者夜间最低血氧饱和度与夜间总睡眠时间、睡眠效率、NREM睡眠时间及呼吸紊乱指数呈显著负相关 (r>0 .3,P <0 .0 5 ) ,与觉醒比例呈显著正相关 (r >0 .5 ,P <0 .0 1)。结论 :SAS患者睡眠结构紊乱突出 ,夜间反复发作的低氧血症对睡眠质量产生较大影响。     

Behavioral correlates of sleep-disordered breathing in older women

STUDY OBJECTIVES: To examine the association between SDB and subjective measures of daytime sleepiness, sleep quality, and sleep related quality of life in a large cohort of primarily community-dwelling older women, specifically considering the relative importance of sleep duration in mediating these associations. DESIGN: Cross-sectional. The functional outcome measures of interest were daytime sleepiness (using the Epworth Sleepiness Scale, ESS), sleep-related symptoms (Pittsburgh Sleep Quality Index, PSQI), and sleep related quality of life (Functional Outcomes of Sleep Questionnaire, FOSQ). ANOVA and regression analyses examined the association between SDB severity (measured by indices of breathing disturbances and overnight oxygen saturation) and sleep time (by actigraphy) and these outcome measures. Regression models were adjusted for age, body mass index (BMI), and a medical comorbidity index. We specifically explored whether associations with indices of SDB were mediated by sleep deprivation by adjusting models for actigraphy-determined average total sleep time (TST) during the night. SETTING: Community-based sample examined in home and outpatient settings. PARTICIPANTS: 461 surviving older women from the multicenter Study of Osteoporotic Fractures were examined during Visit 8 from 2002-03. All participants underwent in-home overnight polysomnography for one night and wrist actigraphy for a minimum of 3 24-h periods and completed the above functional outcomes questionnaires. INTERVENTIONS: N/A. MEASUREMENTS AND RESULTS: Participants were aged 82.9 +/- 3.5 (mean +/- SD) years, had BMI of 27.9 +/- 5.1 kg/m2, and had an apnea-hypopnea index (AHI) of 15.7 +/- 15.1. AHI and TST demonstrated a weak correlation (r = -0.15). ESS score individually demonstrated a modest association with AHI, oxygen desaturation, and TST. The association of ESS score and AHI--but not oxygen desaturation-was attenuated to some extent by adjustment for TST. PSQI and FOSQ scores were not associated with measures of SDB severity or TST. CONCLUSIONS: After adjustment for TST, SDB severity in community-dwelling older women was not independently associated with self-reported daytime sleepiness, although there may be a modest association that is mediated through reduced TST. In older women, SDB severity was not associated with indices of sleep related symptoms or sleep related quality of life.     

Comparing the neurocognitive effects of 40 h sustained wakefulness in patients with untreated OSA and healthy controls

We hypothesized that individuals with untreated obstructive sleep apnea (OSA) would exhibit greater vulnerability to sleep deprivation than healthy controls, due to the additional neurobiological 'load' of chronic sleep fragmentation. After baseline sleep with 8 h time in bed, participants remained awake for 40 h. Psychomotor Vigilance Task (PVT, mean slowest 10% 1/RT), AusEd Driving Simulator task (steering and speed deviation), and subjective sleepiness (Karolinska Sleepiness Scale, KSS) were assessed every 2 h. Nonlinear mixed-effects models were used to characterize individual differences in baseline/average performance, the linear effect of increasing hours awake, circadian amplitude and phase. Eight participants with untreated OSA with mean (SD) age 44.6 (8.4), apnea–hypopnea index (AHI) 49.8 (24.7), Epworth Sleepiness Scale (ESS) 11.9 (4.8) and nine healthy controls age 27.8 (3.7), AHI 4.5 (2.7), ESS 7.3 (2.1) completed the protocol. Baseline KSS was significantly higher (1.4 units, P  = 0.03) in the OSA group and there was a trend toward lower baseline speed deviation on the AusEd ( P  = 0.05). After adjusting for the significant effects of accumulated time awake, circadian amplitude and phase (all P  < 0.005), there was no difference in performance decrements between those with and without sleep apnea in PVT, driving simulator performance and subjective sleepiness ( P  > 0.5). Random-effects modeling confirmed the presence of significant inter-individual variability in vulnerability to sleep deprivation. Patients with OSA did not respond differently to sleep deprivation than healthy controls. As expected, total sleep deprivation led to significant worsening in performance and subjective sleepiness in both groups.     

A randomized, double-blind clinical trial comparing continuous positive airway pressure with a novel bilevel pressure system for treatment of obstructive sleep apnea syndrome

STUDY OBJECTIVES: To obtain efficacy, objective compliance, and self-assessment data from obstructive sleep apnea syndrome (OSAS) patients treated with continuous positive airway pressure (CPAP) or a novel bilevel (NBL) therapy. DESIGN: Randomized, controlled, double-blind trial. SETTING: Home treatment after diagnosis and titration by split-night polysomnography (PSG) in a sleep laboratory. PATIENTS: Twenty-seven adults (22 men) newly referred for suspected OSAS but without concomitant medical or sleep disorders. INTERVENTIONS: If the subject's apnea-hypopnea index was greater than 10 and less than 100, the CPAP was titrated during PSG and then followed by NBL titration. Treatment was randomly and blindly set to either CPAP or NBL mode for 1 month. MEASUREMENTS & RESULTS: There were no significant baseline group differences in age, body mass index, apnea-hypopnea index (mean +/- SD, CPAP group vs NBL group of 46.1 +/- 23.1/hour vs 41.8 +/- 25.8), CPAP requirement, or scores on the Epworth Sleepiness Scale and Functional Outcomes of Sleep Questionnaire. Treatment with CPAP and NBL equivalently reduced the apnea-hypopnea index during the laboratory titration (7.6 +/- 11.9/hour vs. 3.7 +/- 4.4, respectively). At 1 month, there were no significant group compliance differences as determined by percentage of nights with at least 4 hours of use (CPAP, 80.5 +/- 24 vs NBL, 77.6 +/- 24.8) and hours of use per night (CPAP, 5.6 +/- 1.4 hours/night vs NBL, 5.6 +/- 1.7). Similar improvements were seen in scores on the Epworth Sleepiness Scale and Functional Outcomes of Sleep Questionnaire. CONCLUSIONS: The NBL appeared to be as effective as CPAP for the treatment of OSAS but offered no advantages in patients receiving first-time therapy for OSAS.     

Sleep during titration predicts continuous positive airway pressure compliance

STUDY OBJECTIVES: Poor compliance with continuous positive airway pressure (CPAP) has been identified as a significant obstacle in the treatment of obstructive sleep apnea. While previous studies have focused on diagnostic screening variables, side effects, health beliefs, and measures of disease severity, investigators have generally ignored sleep parameters assessed during CPAP titration as predictors of compliance. As the titration night represents patients' initial exposure to nocturnal CPAP treatment, we hypothesized that nocturnal polysomnographic (PSG) variables, representing improved sleep at this time, would predict higher subsequent compliance. DESIGN: Prospective analyses of a sequential case series were undertaken using nocturnal PSG variables during titration as early predictors of CPAP compliance. SETTING: Accredited sleep center. PATIENTS: Seventy-one patients with sleep apnea, aged 31-78 years, with a mean respiratory disturbance index of 62.0 +/- 32.2. Interventions: N/A MEASUREMENTS AND RESULTS: Compliance was calculated as mean hours per night of CPAP use over the initial follow-up period (mean 46.9 days). Standard PSG variables and subjective reports of sleep were used as predictive variables in multivariate analyses. Mean objective compliance was 5.04 hours per night +/- 2.59. Consistent with our hypothesis, the best predictor of compliance was change in sleep efficiency (SE) from diagnostic to titration night [F (1,66) = 17.31, p < .000 (r = .48)], indicating that patients whose sleep improved most on the titration night had the highest levels of compliance. This relationship was also significant after controlling for measures of disease severity obtained during the diagnostic testing night. Importantly, individuals whose sleep improved on the CPAP titration night had nightly compliance rates of approximately 2 hours greater than patients whose sleep did not improve during titration. CONCLUSIONS: The findings suggest that patients' initial experience with CPAP treatment and, in particular, the degree of improvement in sleep during CPAP titration may be crucial factors in determining their subsequent use of this treatment modality.