Changes in cognitive function associated with sleep disordered breathing in older people

OBJECTIVES: Sleep disordered breathing (SDB) is very common in older people and is known to be associated with complaints of impaired daily functioning, including excessive daytime sleepiness and cognitive impairments. As part of a larger study on SDB and aging, it became possible to examine the relationship between SDB and cognition in older men and women. DESIGN: A population-based longitudinal study. SETTING: In-home interviews and home sleep recordings in the greater San Diego area. PARTICIPANTS: Community-dwelling people age 65 and older with high risk for SDB were originally studied from 1981 through 1985 and then followed every 2 years. Data from the 46 subjects who completed Visit 3 and Visit 4 are presented. MEASUREMENTS: Subjects were interviewed in the home about their sleep and medical condition before each visit. Cognitive function was assessed using the Mini-Mental State Examination (MMSE). Daytime sleepiness was based on self-report. Objective sleep was recorded in the home and scored for sleep, apneas and hypopneas, and oximetry variables. RESULTS: Increases in respiratory disturbance index (RDI) (P= .036) and increases in daytime sleepiness (P= .002) were associated with decreases in cognitive performance (i.e., increases in cognitive impairment). Increases in RDI were also associated with increases in daytime sleepiness (P= .012). Change in MMSE scores was therefore regressed onto changes in RDI, daytime sleepiness, age, and education, resulting in decreases in MMSE scores being associated with increases in daytime sleepiness (P= .019) but not with changes in RDI (P= .515). There was no significant relationship between changes in oxygen saturation levels and changes in MMSE. CONCLUSIONS: The results of this study suggest that declining cognitive function is associated primarily with increases in daytime sleepiness. Although cognitive decline was also associated with increases in RDI, this association did not hold in the more inclusive model which also included variable of SDB, oximetry, sleep and subjective report. One theoretical model could suggest that any relationship between SDB and cognitive function may be mediated by the effect of SDB on daytime sleepiness. These results suggest that older patients suffering from mild to moderate SDB may benefit from the treatment of SDB, even if they are not markedly hypoxemic.     

Sleep-related respiratory disturbance and dementia in elderly females

Sleep-related respiratory disturbance was studied with a microprocessor-based portable monitoring system in female residents of a retirement village aged greater than or equal to 75 years. Comparisons were made between 29 demented subjects Mini-Mental State Examination Score (MMSE) less than 21 and 48 controls (MMSE greater than 25). Respiratory disturbance index (RDI, the number of episodes of apnea and hypopnea/hour of total sleep time) was higher in the demented subjects: mean RDI (+/- SD) 18.5 +/- 18.6 vs 7.3 +/- 10.8, p = .004. The number of minutes per hour of sleep spent with disturbed breathing was greater in demented subjects than in controls (p = .01). These differences between demented subjects and controls persisted after adjustment for age and relevant medical history. Other possible confounders, namely body mass index and use of sedatives, were not significant. We conclude that respiratory disturbance during sleep is more prevalent in elderly demented females than in controls.     

Relation of measures of sleep-disordered breathing to neuropsychological functioning

Sleep-disordered breathing (SDB) has been associated with neuropsychological (NP) deficits. The extent to which such effects are attributable to unmeasured confounders or selection biases, or are manifest across a range of SDB is unclear. The relationship of SDB with a broad range of NP functions was examined in 100 volunteers with a spectrum of SDB and without underlying comorbidity. Factor analysis suggested that the NP tests could be summarized as four constructs: declarative memory, signal discrimination, working memory, and set shifting. These factors plus vigilance were dependent variables. Independent variables were age, the respiratory disturbance index (RDI), a sleepiness score, the arousal index, and sleep-associated hypoxemia. Factors "declarative memory" (measuring 25% of the common variance, alpha = 0.95), "signal discrimination" (10% variance, alpha = 0.70), and "working memory" (9% variance, alpha = 0.52) were each significantly, linearly predicted by hypoxemia and/or the RDI, with no evidence for significant threshold effects. SDB measures accounted for 4-6% of the variance in NP constructs. In contrast, sleepiness best predicted vigilance. Thus, adverse exposures (hypoxemia or RDI) during sleep may negatively influence NP functions in a dose-response relationship, and, other than vigilance, these effects may not be directly attributable to sleepiness.     

Heart rate variability during sleep in snorers with and without obstructive sleep apnea.

Changes in sympathetic and vagal tone may be the substrate for the development of cardiac arrhythmias in patients with obstructive sleep apnea (OSA). The cardiovascular responses in the traditional autonomic tests show great interindividual and intraindividual variations. During sleep there are repetitive modifications of heart rate (HR) that are not influenced by psychologic factors or the patient's cooperation. For this reason, we evaluated HR modifications in relation to spontaneous body movements (BM) and sleep apneas during nonrapid eye movement (NREM) and rapid eye movement (REM) sleep in habitual snorers with normal and pathologic respiratory disturbance index (RDI). From 132 consecutive patients referred to our sleep center for habitual snoring and/or daytime somnolence, we selected 35 male patients younger than 60 years without clinical evidence of autonomic dysfunction. They were divided into three groups: group A (RDI < 10); group B (RDI > 10 and < 20); and group C (RDI > 20). No significant difference was found among the three groups in the HR variability related to BM. In the evaluation of bradytachyarrhythmias related to apneic events of 20 to 30 s, we found a significant difference between group A and the other two groups. In patients with RDI > 10, a reduced HR variability related to a reduced sympathetic tone in the post-apnea phase was observed. Some authors suggested that an HR increase during the post-apnea period can be used as an index of "brainstem arousal." Our results seem to indicate a reduced apnea-related "arousability" in patients with RDI > 10. This finding might be one of the factors contributing to the worsening of OSA.     

Pre-eclampsia is associated with sleep-disordered breathing and endothelial dysfunction.

Pre-eclamptic toxaemia (PET) may be associated with both endothelial dysfunction (ED) and sleep-disordered breathing (SDB). It was hypothesised that females with PET would demonstrate both SDB and ED, and that a correlation between these two would suggest a potential causative association. A total of 17 females with PET and 25 matched females with uncomplicated pregnancy were studied. They underwent a nocturnal ambulatory sleep study (using Watch_PAT100) and noninvasive evaluation of endothelial function utilising the reactive hyperaemia test (using Endo_PAT 2000). A higher ratio of post- to pre-occlusion pulse-wave amplitude (endothelial function index (EFI)) indicated better endothelial function. Females with PET had a significantly higher respiratory disturbance index (RDI) and lower EFI than controls (18.4+/-8.4 versus 8.3+/-1.3.h(-1), and 1.5+/-0.1 versus 1.8+/-0.1, respectively). Blood pressure significantly correlated with RDI and with EFI. EFI tended to correlate with RDI. In conclusion, these results suggest that both sleep-disordered breathing and endothelial dysfunction are more likely to occur in females with pre-eclamptic toxaemia than in females with uncomplicated pregnancies. The current authors speculate that respiratory disturbances contribute to the functional abnormality of the blood vessels seen in females with pre-eclamptic toxaemia, although causality cannot be determined based on this study.     

Prevalence of snoring and sleep-disordered breathing in a group of commercial bus drivers in Hong Kong

Objectives: To assess the prevalence of sleep‐­disordered breathing (SDB) and its associated symptoms in a group of commercial bus drivers in Hong Kong. Methods: Two hundred and sixteen of 410 bus drivers from three different shifts were interviewed with the Sleep & Health Questionnaire (SHQ) and the Epworth sleepiness scale (ESS) at a Hong Kong bus depot. Seventeen subjects from each shift were then randomly selected for at‐home sleep study using the Mesam IV device (Madaus Medizin?Elektronik, Freiburg, Germany). Results: There were 207 men and nine women (mean age 42.4 ± 7.5 years; body mass index (BMI) 25.4 ± 4.5 kg/m²; ESS 5.3 ± 4.2). From the SHQ it was discovered that: (i) daytime sleepiness was reported by 87 subjects (40%), (ii) snoring ≥ 3 times per week was reported by 80 subjects (37%), (iii) witnessed apnoea was reported by 17 subjects (7.9%) and (iv) 29 subjects (13.4%) reported having fallen asleep during driving. Among the 51 subjects who underwent the at‐home sleep study: (i) 31 subjects (61%) had respiratory disturbance index (RDI) ≥ 5 per hour of sleep, (ii) 21 subjects (41%) had RDI ≥ 10 per hour of sleep, (iii) 12 subjects (24%) had RDI ≥ 15 per hour of sleep and (iv) 35 subjects (68.6%) snored objectively ≥ 10% of the night. Ten subjects (20%) had RDI ≥ 5 and sleepiness at work, while five subjects (9.8%) had RDI ≥ 5 and ESS > 10. No significant differences were noted in the SHQ responses, ESS, objective snoring or RDI among the three groups. Multiple regression analysis showed that BMI and witnessed apnoea were the only positive independent predictors of RDI. Conclusions: This study showed a high prevalence of objective snoring and SDB in a group of commercial bus drivers. Neither self‐reported sleepiness nor the ESS could identify subjects with SDB. (Intern Med J 2002; 32: 149?157)     

Prevalence of snoring and sleep-disordered breathing in a student population

INTRODUCTION: The prevalence of snoring and sleep-disordered breathing (SDB) in young adults in Southeast Asian countries is unknown. We aim to determine the symptoms and prevalence of SDB in a university student population using a questionnaire survey followed by home sleep monitoring. METHODS: The Sleep and Health Questionnaire (a modified version of the Specialized Centers of Research Sleep Questionnaire, translated into Chinese) was distributed to all first-year students (1,306 male and 1,757 female) enrolled in the Chinese University of Hong Kong. Subsequently, those students who returned the questionnaires were randomly chosen to undergo portable home sleep monitoring using the MESAM IV device (Madaus Medizin-Elektronik; Freiburg, Germany). RESULTS: A total of 1,910 replies were obtained from 3,063 questionnaires sent by mail (response rate, 62.4%). The female to male ratio was 1.8:1, with mean age of 19.4 years (SD, 1.3 years) and mean body mass index (BMI) of 20.0 (SD, 2.5). Overall, 25.7% of subjects reported snoring; 10.7% and 42.1% reported impaired performance ability and daytime sleepiness, respectively. Of the 88 subjects who underwent overnight sleep monitoring, 66 subjects (75%) were snorers and 8 subjects (9%) snored > 10% of the night. Male subjects had a higher BMI (p < 0.001) and tended to snore more often than female subjects (p = 0.06). Subjects with an oxygen desaturation index (ODI) > or = 3 had a BMI > 22 (p < 0.05). On sleep study, nine subjects (10.2%) and two subjects (2.3%) had a respiratory disturbance index (RDI) > or = 3 and an RDI > or = 5, respectively, associated with self-reported sleepiness, giving a minimum estimated prevalence of SDB as 0.1% (RDI > or = 5) in the study population. There was no correlation between recorded snoring with either RDI or self-reported sleepiness. Questionnaire responses, neck circumference, and alcohol consumption did not predict the occurrence of SDB. CONCLUSION: Snoring was prevalent, while SDB was uncommon in this student population. However, snoring and self-reported symptoms by questionnaire were poor predictors for SDB. Male gender showed a trend as an independent predictor for snoring, but not for SDB.     

A 3-year longitudinal study of sleep disordered breathing in the elderly

Limited and controversial data exist on the natural evolution of sleep disordered breathing (SDB) in untreated individuals. This study examines the evolution of SDB over a 3-yr period in a community-based sample of elderly subjects. From the initial cohort of 854 healthy subjects aged mean±sd 68.4±0.8 yrs, 519 untreated subjects accepted clinical and instrumental follow-up 3.6±1.6 yrs later. SDB was defined as a respiratory disturbance index (RDI) >15 events·h(-1). At baseline, 202 (39%) subjects had an RDI ≤15 events·h(-1) and 317 (61%) had an RDI >15 events·h(-1). 3 yrs later, 280 (54%) subjects were non-SDB and 239 (46%) had SDB. Between evaluations, the RDI decreased from 22.3±16.2 to 16.4±13.0 events·h(-1), with a greater decrease in the number of cases with an RDI >30 events·h(-1) that in those with RDI ≥30 events·h(-1). In the non-SDB group, 81% had a stable RDI and 19% increased their RDI by a mean of 13.7 events·h(-1). In the SDB group, the RDI decreased to values ≤15 events·h(-1) in 36.6% of cases, 63.4% still having SDB. The RDI changes did not depend on weight changes. In healthy elderly subjects, the prevalence and severity of SDB did not show a tendency toward natural worsening, some cases having improvement or a remission independent of weight changes. These findings also suggest that in the elderly, natural SDB progression is still hypothetical.     

Measurement of sleep-related breathing disturbances in epidemiologic studies. Assessment of the validity and reproducibility of a portable monitoring device

The feasibility and reliability of measuring sleep-related breathing disorders with a portable monitor (PM) were assessed in a heterogeneous population, consisting of 31 patients recruited from a sleep laboratory and pulmonary disease clinic, 16 participants in a genetic-epidemiologic study of sleep apnea, and four volunteers with no specific sleep complaints. The validity of measurements made by the PM was assessed with comparisons of respiratory parameters made with the PM to those determined with in-hospital polysomnography (PSG) (25 studies). Reproducibility was assessed in 29 subjects who underwent in-home monitoring on two occasions. There was a high level of agreement between the number of respiratory events (apneas or hypopneas) per hour of estimated sleep (respiratory disturbance index, RDI) recorded with the PM and PSG and log-transformed (r = 0.96). Using a RDI of greater than or equal to 10 to define "abnormality," 20 of the 21 subjects who would have been classified as abnormal with PSG were classified similarly with use of the PM. A similar high level of agreement was demonstrated for the log-transformed RDI determined with replicate in-home studies (r = 0.94). No evidence of a "first-night effect" for the RDI was suggested in studies performed with the PM; ie, RDI was 18.4 +/- 27.7 and 17.4 +/- 25.7 (mean +/- SD) for first and second night studies, respectively (p = 0.21). A second compared with an initial study with the PM would have resulted in reclassification of abnormality based on an RDI of greater than or equal to 10 in one subject. These findings suggest that measurement of the RDI with in-home monitoring provides a valid and highly reproducible index for assessment of sleep-related respiratory disturbances for use in epidemiologic studies of general populations.     

Polysomnographic characteristics in patients with Prader-Willi syndrome

To evaluate the occurrence of sleep-disordered breathing and to clarify the characteristics of sleep among patients with Prader-Willi syndrome (PWS). Overnight continuous EEG-polysomnographic studies were performed in 30 patients with PWS (16 males and 14 females; mean age, 7.4 +/- 4.1 years; age range, 1-19 years) unselected for sleep disturbance. The baseline arterial oxygen saturation (SpO2) was 96.6 +/- 0.6%, with a nadir of 77.2 +/- 10.2%. The rapid eye movement (REM) latency was 67.4 +/- 30.0 min. The percent of total sleep time spent in sleep stages 1, 2, slow wave, and REM were 13.1 +/- 8.2%, 41.9 +/- 10.5%, 21.5 +/- 9.4%, and 21.1 +/- 5.7%, respectively. The respiratory disturbance index (RDI) was 5.8 +/- 3.7/hr and desaturation index (DI) was 8.1 +/- 7.3/hr, respectively. Age-adjusted BMI was associated with more severe hypoxemia during sleep (baseline SpO2, r = -0.53, P < 0.01; nadir SaO2, r = -0.65, P < 0.01; RDI, r = 0.37, P < 0.05; DI, r = 0.53, P < 0.01) and more sleep disruption (arousal index, r = 0.46, P < 0.01). There were no significant associations between gender or genotype pattern (deletion vs. uniparental disomy) and the results of polysomnography. Sleep hypoxemia and sleep disruption are more prevalent in patients with PWS than in normal children. Obesity in these patients is associated with more severe sleep-disordered breathing.     

Nightly variation in sleep-related respiratory disturbance in older adults

This study investigated variation in respiratory disturbance during sleep. Sixty-six healthy elderly subjects (mean age = 67.2) underwent two consecutive nights of polysomnography. Respiratory disturbance was assessed by Respiratory Disturbance Index (RDI), the number of events per hour of sleep. Results indicated an increase in RDI from Night 1 to Night 2. Fourteen subjects increased their RDI by over 2.5, and eight by over 5.0, events per hour on Night 2. The increase was not a function of increased REM on Night 2. Age was positively related to RDI on individual lab nights but unrelated to nightly variation in RDI. Subjects without complaints of insomnia were more likely to show increases in RDI, perhaps reflecting the sounder sleep of this group on the second laboratory night. This study suggests that a single night of polysomnography is likely to underestimate the absolute level of respiratory disturbance seen in a subsequent recording night. Studies placing prevalence of such disturbance in the elderly at approximately 30% are thus likely to be underestimates. Whether this "error" is important will depend ultimately upon the meaning of various absolute levels of respiratory disturbance in healthy older persons.     

Nightly variation in sleep-related respiratory disturbance in older adults

This study investigated variation in respiratory disturbance during sleep. Sixty-six healthy elderly subjects (mean age = 67.2) underwent two consecutive nights of polysomnography. Respiratory disturbance was assessed by Respiratory Disturbance Index (RDI), the number of events per hour of sleep. Results indicated an increase in RDI from Night 1 to Night 2. Fourteen subjects increased their RDI by over 2.5, and eight by over 5.0, events per hour on Night 2. The increase was not a function of increased REM on Night 2. Age was positively related to RDI on individual lab nights but unrelated to nightly variation in RDI. Subjects without complaints of insomnia were more likely to show increases in RDI, perhaps reflecting the sounder sleep of this group on the second laboratory night. This study suggests that a single night of polysomnography is likely to underestimate the absolute level of respiratory disturbance seen in a subsequent recording night. Studies placing prevalence of such disturbance in the elderly at approximately 30% are thus likely to be underestimates. Whether this “error” is important will depend ultimately upon the meaning of various absolute levels of respiratory disturbance in healthy older persons.     

Cognitive disturbances in non-demented subjects: heterogeneity of neuropsychological pictures

The aim of this study was to individuate different clinical and cognitive pictures among non-demented subjects reporting cognitive disturbances. We evaluated 75 subjects referring to Alzheimer's Disease Assessment Unit of IRCCS C. Mondino, Pavia, who complained memory disturbances in absence of impairment in every day activities, not fitting DSM-IV criteria for dementia (MMSE>24). The subjects underwent neurological examination, blood chemistry and neuroimaging. The neuropsychological evaluation included tests exploring language, short- and long-term memories, logical abilities, attentive and visuo-constructional functions. Fifty-two patients fitted the criteria for mild cognitive impairment (MCI); twenty-three subjects had a neuropsychological evaluation within normal range for age and schooling; they were significantly younger and better educated and presented higher scores at scale for depression and anxiety than the MCI patients. In the MCI group, on the basis of cognitive profile and neuroimaging, different subtypes could be distinguished. Subjective cognitive complaints represent a heterogeneous condition, which can develop into different clinical pictures. It is, therefore, important to individuate specific clinic and neuropsychological profiles, possible predictive of different evolution.     

Classification of sleep-disordered breathing

Increasing recognition of sleep-disordered breathing (SDB) and its morbidity have prompted reevaluation of techniques to identify respiratory events during sleep. The present study was designed to evaluate the utility of various metrics of SDB and to identify the optimal respiratory metric that objectively correlates to symptoms of excessive daytime somnolence (EDS). Metrics were derived from combinations of conventional apnea/hypopnea, flow limitation events (transient elevated upper airway resistance identified by characteristic flattening on the flow/time tracing, using a noninvasive nasal cannula technique), desaturation, and arousal. A total of 137 subjects underwent clinical evaluation and nocturnal polysomnogram. In 34 randomly selected subjects, the best metrics for discriminating between 13 subjects with no EDS/snoring and 21 patients with EDS and snoring were identified by receiver operator curve analysis. Of the metrics and cut points tested, a total respiratory disturbance index (RDI(Total), sum of apneas, hypopnea, and flow limitation events) of 18 events/h was found to have the best discriminant ability (100% sensitivity and 96% specificity). Prospective testing of this metric was then performed with the remaining 103 subjects (14 nonsnoring non-EDS, 21 snoring non-EDS, 68 snoring with EDS). Using this cutoff of 18 events/h, we obtained 71% sensitivity and 60% specificity for identifying subjects with EDS. We conclude that, in subjects with upper airway dysfunction, an index that incorporates all respiratory events provides the best quantitative physiological correlate to EDS.     

Neuropsychological function and sleep

Neuropsychological function and sleep in the aged have been studied for more than 20 years. The elderly studies focused on psychometric correlates of sleep architecture (REM, SWS, and various measures of sleep disturbance). More recently, psychometrics have been related to breathing disturbance in sleep, but the interpretation of such deficits in terms of hypoxemia and sleepiness remains controversial. To a large extent, all such relationships may depend upon the medical risk factors and chronic conditions affecting both neuropsychological function and sleep in old age.     

Prevalence and mechanisms of diurnal hypercapnia in a sample of morbidly obese subjects with obstructive sleep apnoea

It is well known that obstructive sleep apnoea is especially frequent in the morbidly obese. In these subjects diurnal chronic hypercapnia, whose mechanism is still debated, may be present. Our study was performed to evaluate the prevalence and the mechanism of diurnal hypercapnia in the morbidly obese affected by obstructive sleep apnoea. From a population referred to our centre because of suspicion of sleep related breathing disorders, we selected 285 subjects without cardiopulmonary, neuromuscular or endocrinological diseases: 89 (36 M and 53 F, aged 46+/-13 years) had body mass index (BMI) > or = 40 kg m(-2) (MO group: morbidly obese subjects) and 196 (99 M and 97 F, aged 48+/-16 years) had BMI <40 kg m(-2) (NMO group: non-morbidly obese subjects). Then the MO group was divided into three subgroups: normocapnic subjects without obstructive sleep apnoea, normocapnic subjects with obstructive sleep apnoea, hypercapnic subjects with obstructive sleep apnoea; while we found no hypercapnic subject without obstructive sleep apnoea. All subjects underwent anthropometric evaluations and bioelectrical impedance analyses, respiratory function tests and arterial blood gas analysis, a modified version of the Sleep and Healthy questionnaire and a full night polysomnography. Our results showed that hypercapnia (PaCO2 > or = 45 mm Hg) associated with obstructive sleep apnoea [respiratory disturbance index (RDI) > or = 10 h(-1)] was found in 27% of the morbidly obese subjects, but only in 11% of the nonmorbidly obese ones (P<0.01). The comparison among the three subgroups, in which we divided the morbidly obese subjects, shows that those with hypercapnia and obstructive sleep apnoea had significantly more important ventilatory restrictive defects [forced vital capacity (FVC)% of pred 73.27+/-14 81 vs. 82.37+/-16.93 vs. 87.25+/-18.14 respectively; total lung capacity (TLC)% of pred 63.83+/-16.35 vs. 79.11+/-14.15 vs. 87.01+/-10.5], a significantly higher respiratory disturbance index (RDI 46.34+/-26.90 vs. 31.79+/-22.47 vs. 4.98+/-3.29) a longer total sleep time with oxyhaemoglobin saturation<90% [total sleeptime (TST)SaO2<90% 63.40+/-33.86 vs. 25.95+/-29.34 vs. 8.22+/-22.12] and a lower rapid eye movement (REM) stage (9.5+/-1.2 vs. 14.0+/-0.9 vs. 17.05+/-1.2) than normocapnic subjects with obstructive sleep apnoea or subjects without obstructive sleep apnoea. The best model to predict PaCO2 resulted from a combination of TSTSaO2<90% (r2 = 0.22, P<0.001), forced expiratory volume in 1 sec (FEV1)% of pred (r2 = 0.09, P<0.01), FVC % of pred (r2 = 0.075, P<0.01). In conclusion our study suggests that diurnal hypercapnia is frequently associated with obstructive sleep apnoea in the morbidly obese without chronic obstructive pulmonary disorder (COPD) and that ventilatory restriction and sleep related respiratory disturbances correlate to diurnal hypercapnia.     

Mean blood pressure, pulse pressure and grade of hypertension in untreated hypertensive patients with sleep-related breathing disorder

OBJECTIVE: To test the hypothesis that sleep-related breathing disorder (SRBD) is associated with increasing severity of cardiovascular risk markers. DESIGN: A cross-sectional study of sleep laboratory patients. SETTING: University Hospital Sleep Disorders Centre. PATIENTS: We studied 591 patients referred for a sleep study, all of them without a history of systemic hypertension. INTERVENTIONS: Clinical interview, two unattended sleep studies, and assessment of office blood pressure, cholesterol concentration, alcohol and nicotine consumption and daytime blood gases. MAIN OUTCOME MEASURE: Post-hoc analysis of different cardiovascular risk markers: mean blood pressure, pulse pressure, and the type and grade of systemic hypertension. RESULTS: Patients were classified as normotensive (blood pressure < 140/90 mmHg, n = 228) or hypertensive (blood pressure > or = 140/90 mmHg, n = 363) according to office blood pressure measurements. Mixed (systolic and diastolic) hypertension was the most common type of hypertension (n = 182), followed by isolated diastolic hypertension (n = 101), borderline isolated systolic hypertension (n = 70), and isolated systolic hypertension (n = 10). The frequency of mixed hypertension increased with SRBD activity (P < 0.05) and respiratory disturbance index (RDI; the number of breathing disorders per hour of estimated sleep time) was increased in those with mixed hypertension compared with those with normotension (24.8 compared with 15.7; t test: P < 0.01). In hypertensive patients classified as having grades 1 -3 of hypertension (n = 265, 80 and 18, respectively), there was a progressive increase in RDI (18.9, 27.2 and 30.3, respectively, P < 0.01). Mean blood pressure increased significantly with RDI. Pulse pressure increased significantly with age (P < 0.001), but was unrelated to the degree of SRBD. CONCLUSION: We conclude that mean blood pressure and the severity of hypertension, but not pulse pressure, increase with the severity of the SRBD.     

Follow-up assessment of CPAP efficacy in patients with obstructive sleep apnea using an ambulatory device based on peripheral arterial tonometry

This study aimed to assess the accuracy of a wrist-worn device based on peripheral arterial tonometry (Watch_PAT 100) to detect residual episodes of respiratory disturbance during continuous positive airway pressure (CPAP) therapy. Concurrent polysomnography was used as the reference standard to identify sleep disordered breathing (SDB) events. The study was conducted in three sleep laboratories affiliated with tertiary care academic medical centers. Seventy patients using CPAP to treat obstructive sleep apnea for at least 3 months, following an in-laboratory titration to determine the optimal therapeutic positive airway pressure, participated in this study. Symptoms indicating suboptimal therapy were not required for participation, but self-reported adherence to CPAP therapy was necessary for inclusion. Interventions are not applicable in this study. The accuracy of the PAT-derived respiratory disturbance index (PAT RDI scored by automated algorithm) to detect residual SDB on CPAP was assessed against polysomnography (PSG) using Bland–Altman analysis, receiver–operator characteristic (ROC) curves, and likelihood ratios for increasing (LR+) and decreasing (LR−) the probability of moderate–severe SDB in the study population. Respiratory events on the PSG were quantified using standard criteria for research investigations (“Chicago criteria”) to yield a PSG RDI.C. Based on the PSG results, 19% of the participants had moderate–severe SDB (PSG RDI.C>15 events per hour) on their prescribed pressure. For PAT RDI >15 events per hour, the area under the ROC curve was 0.95 (SE 0.03, p<0.0001, 95% CI 0.89 to 1.00), the LR+ was 8.04 (95% CI 3.64–17.7), and the LR− was 0.17 (95% CI 0.05–0.62). The mean difference between the PAT RDI and PSG RDI.C was three (2SD 14.5) events per hour. Therefore, residual moderate–severe SDB on CPAP was not uncommon in a multicenter population self-reporting adherence to CPAP therapy to treat obstructive sleep apnea. The Watch_PAT device accurately identified participants with moderate–severe SDB while using CPAP in the attended setting of a sleep laboratory.     

A visual recognition memory test for the assessment of cognitive function in aging and dementia

Young, non-demented elderly, and elderly demented subjects were administered a computerized visual recognition memory task. In the task, subjects were instructed to point out the new object from a group of objects whose number was progressively incremented. The test was subject-paced and made use of face-valid stimulus materials; it is closely comparable to tests developed for memory assessment in non-human primates that are sensitive to the effects of hippocampal ablation. The present task was found to elicit significant differences in performance between young and non-demented aged subjects, between the non-demented and demented elderly, and between demented subjects in the early and more advanced stages of senile dementia of the Alzheimer type (SDAT). In a discriminant analysis, the visual recognition memory test scores correctly classified 72.6% of the aged subjects and early SDAT patients. No significant difference in task performance was found between SDAT patients and demented patients with a significant cerebrovascular etiological component. Thus, although the task does not appear to be suitable for diagnostic purposes it would be useful for the assessment of treatment effects upon age-related cognitive dysfunction.