Sleep apnea and the risk of dementia: A systematic review and meta-analysis.

Sleep apnea (SA) is potentially a modifiable risk factor for dementia. However, its associations to specific aetiologies of dementia remain uncertain. A systematic review and meta-analysis of cohort studies investigating the association between sleep apnea and specific aetiologies of dementia, including Alzheimer's disease (AD), Parkinson's disease (PD), Lewy body dementia (LBD), vascular dementia (VaD), and frontotemporal dementia (FTD) was performed. The use of biomarkers to support clinical diagnoses in eligible studies was collected. Eleven studies were included, comprising 1,333,424 patients. Patients with sleep apnea had an increased risk of developing any type of neurocognitive disorder (HR: 1.43 [95% CI 1.26-1.62]), Alzheimer's disease (HR: 1.28 [95% CI 1.16-1.41]), and Parkinson's disease (HR: 1.54 [95% CI 1.30-1.84]). No statistically significant association was found for vascular dementia. One study reported a two-fold increased risk for Lewy body dementia (HR: 2.06 [95% CI 1.45-2.91]). No studies investigated the risk for frontotemporal dementia and none of the studies reported results pertaining to biomarkers. Sleep apnea is associated with a significantly increased risk of dementia, particularly for Alzheimer's disease and Parkinson's disease, but not for vascular dementia. Future studies should look at the impact of sleep apnea on specific dementia biomarkers.

Sleep-disordered breathing and daytime postural stability.

OBJECTIVE: Postural stability depends on the coordination of the central nervous system with visual sense, proprioceptive and vestibular information. Sleep deprivation has been shown to affect this function. The objective of our study was to assess the effects of sleep-disordered breathing (SDB) on postural stability. METHODS: 158 subjects referred for suspected SDB had an overnight sleep study and were placed on a posturographic platform in late afternoon. This platform allows measuring the centre of pressure (CoP) oscillations and to calculate: total displacement of CoP in X and Y axes, mean speed of CoP displacement and the length as function of surface (LFS) ratio (length of CoP displacement/surface of CoP trajectory). RESULTS: 98 men and 60 women were included. Mean age±SD was 45.4±5.5 years old, body mass index (BMI) 27.5±5.6 kg/m(2) and apnoea-hypopnoea index (AHI) 13.6±16.1/h. AHI was <5/h in 64 (41%) subjects, 5-15/h in 43 (27%), 15-30/h in 30 (19%) and >30/h in 21 (13%). In patients with an AHI >5/h versus AHI <5/h, we observed an important increase in LFS (+21%, p<0.001), in XY length (+23%, p<0.001) and in mean speed (+23%, p<0.001). After controlling for age, BMI and sleepiness (Epworth) in multivariate regression models, there was a positive association between all nocturnal breathing parameters (specifically: mean SpO2, AHI, oxygen desaturation index 3% and % time with SpO2 <90%) and the main stability outcomes (all p<0.05). CONCLUSIONS: SDB severity, especially the mean nocturnal SpO2 level, is associated with impaired daytime postural stability.

Scoring criteria for portable monitor recordings: a comparison of four hypopnoea definitions in a population-based cohort.

RATIONALE: Limited-channel portable monitors (PMs) are increasingly used as an alternative to polysomnography (PSG) for the diagnosis of obstructive sleep apnoea (OSA). However, recommendations for the scoring of PM recordings are still lacking. Pulse-wave amplitude (PWA) drops, considered as surrogates for EEG arousals, may increase the detection sensitivity for respiratory events in PM recordings. OBJECTIVES: To investigate the performance of four different hypopnoea scoring criteria, using 3% or 4% oxygen desaturation levels, including or not PWA drops as surrogates for EEG arousals, and to determine the impact of measured versus reported sleep time on OSA diagnosis. METHODS: Subjects drawn from a population-based cohort underwent a complete home PSG. The PSG recordings were scored using the 2012 American Academy of Sleep Medicine criteria to determine the apnoea-hypopnoea index (AHI). Recordings were then rescored using only parameters available on type 3 PM devices according to different hypopnoea criteria and patients-reported sleep duration to determine the 'portable monitor AHIs' (PM-AHIs). MAIN RESULTS: 312 subjects were included. Overall, PM-AHIs showed a good concordance with the PSG-based AHI although it tended to slightly underestimate it. The PM-AHI using 3% desaturation without PWA drops showed the best diagnostic accuracy for AHI thresholds of ≥ 5/h and ≥ 15/h (correctly classifying 94.55% and 93.27% of subjects, respectively, vs 80.13% and 87.50% with PWA drops). There was a significant but modest correlation between PWA drops and EEG arousals (r=0.20, p=0.0004). CONCLUSION: Interpretation of PM recordings using hypopnoea criteria which include 3% desaturation without PWA drops as EEG arousal surrogate showed the best diagnosis accuracy compared with full PSG.

Oscillating Positive Airway Pressure Versus CPAP for the Treatment of Obstructive Sleep Apnea.

Although continuous positive airway pressure (CPAP) is the most effective therapy for obstructive sleep apnea (OSA), it is not always well tolerated by the patients. Previous physiological studies showed that pressure oscillations applied to the pharynx could activate upper airway muscles, but it is not clear whether these pressure oscillations could be tolerated during sleep in OSA patients. The aim of this study was to assess the tolerance of oscillating positive airway pressure (O-PAP) (a CPAP device delivering high-frequency pressure oscillations to the upper airway) compared to CPAP. Fourteen OSA patients currently on CPAP [age 59.9 ± 10.1 years old, BMI 34.8 ± 7.2 kg/m(2), initial apnea-hypopnea index (AHI): 58.7 ± 25.2 events/h] used O-PAP or CPAP on two consecutive nights under polysomnography, in a single-blind randomized crossover design to assess sleep quality. A subtherapeutic pressure (70% of the optimal titrated pressure) was applied in both conditions and the residual AHI with each technique was also compared. There was no difference in measured or perceived sleep quality between the two treatment modalities (sleep efficiency 90.0% versus 88.1%, p = 0.54). Despite the small sample, we also found a trend toward a decrease in residual respiratory events with O-PAP compared to CPAP (median AHI 14.3 versus 20.5/h, p = 0.194). The good tolerance of O-PAP and the positive trend toward a reduction in residual AHI should stimulate further research on the effects of O-PAP in OSA patients.

Application and interpretation of an interferon-gamma release assay: Results of an audit in a Canadian centre.

BACKGROUND: Interferon-gamma release assays (IGRAs) are newly approved for diagnosing latent tuberculosis infection (LTBI). An internal audit was conducted to review the use of a newly implemented IGRA at the Hôpital du Sacré-Coeur de Montréal (Montréal, Québec) to evaluate its concordance with Canadian recommendations and its implication on diagnosis. METHODS: From April 2007 to January 2009, all Quantiferon TB Gold In-Tube (QFT, Cellestis inc, USA) tests performed in at the Hôpital du Sacré-Coeur de Montréal were retrieved. Strategies used to investigate LTBI and clinical interpretation of test results were compared with the local algorithm, which is derived from the current national guidelines. RESULTS: A total of 200 patients tested with QFT were included in the analysis. LTBI investigation and QFT testing were considered to be appropriate in 87.5% and 66.5% of patients, respectively. Overall, 67 QFT tests were performed inappropriately; 25 were performed when a LTBI investigation was not indicated and 42 were performed whe LTBI interpretation was possible with the result of the tuberculin skin test alone. Among the 175 patients investigated appropriately for LTBI, 49 QFT tests (28%) were interpreted incorrectly; 32 patients (at high risk of developing active tuberculosis) had a positive tuberculin skin test and a negative QFT result wrongly interpreted as being negative for LTBI and 13 patients should have undergone further LTBI investigations. CONCLUSION: Globally, the present study revealed that there are discrepancies on how the IGRA was employed and interpreted in a Montreal hospital and that strict compliance to the guidelines could significantly reduce errors in interpretation.

HISTORIQUE: Les tests de libération d'interféron gamma (TLIG) ont récemment été approuvés pour diagnostiquer une infection tuberculeuse latente (ITBL). Une vérification interne a été organisée pour examiner l'utilisation d'un nouveau TLIG à l'Hôpital du Sacré-Cœur de Montréal (Montréal, Québec) ainsi que pour en évaluer la concordance avec les recommandations canadiennes et les conséquences sur le diagnostic. MÉTHODOLOGIE: D'avril 2007 à janvier 2009, les chercheurs ont extrait tous les tests Quantiferon TB Gold In-Tube (QFT) effectués à leur centre. Ils ont comparé les stratégies utilisées pour évaluer l'ITBL et l'interprétation clinique des résultats des tests avec leur algorithme local, dérivé des lignes directrices nationales à jour. RÉSULTATS: Au total, 200 patients ayant subi le test QFT ont participé à l'analyse. L'examen de l'ITBL et le test QFT ont été considérés comme convenables chez 87,5 % et 66,5 % des patients, respectivement. Dans l'ensemble, 67 tests QFT avaient été mal exécutés, soit 25 lorsque l'examen de l'ITBL n'était pas indiqué et 42 lorsqu'il était possible d'interpréter l'ITBL grâce aux seuls résultats du test cutané à la tuberculine. Chez les 175 patients ayant subi des examens convenables de l'ITBL, 49 tests QFT (28 %) avaient été mal interprétés. En effet, 32 patients (très vulnérables à une tuberculose active) présentaient un test cutané à la tuberculine positif et un résultat négatif du test QFT interprété à tort comme négatif à l'ITBL, tandis que 13 patients auraient dû subir des examens plus approfondis de l'ITBL. CONCLUSION: Globalement, la présente étude a révélé des divergences dans l'utilisation du TLIG au centre et établi qu'un respect rigoureux des lignes directrices pourrait réduire considérablement les erreurs d'interprétation.