Faculty Bibliography

BACKGROUND: Following the World Trade Center disaster, a large number of individuals involved in rescue and recovery activity were exposed to significant amounts of dust, and reported symptoms of chronic nasal and sinus inflammation. An unusually high prevalence of obstructive sleep apnea (OSA) has also been observed in this World Trade Center Responder population. This project aims to examine the relationship between nasal pathology and OSA. Our hypothesis is that increased nasal resistance due to nasal inflammation predisposes to OSA in this population. Continuous Positive Airway Pressure (CPAP) is the standard therapy for OSA but despite its efficacy has poor adherence. Subjects with high nasal resistance may have greater difficulty in tolerating this therapy than those who do not have high nasal resistance. Reduction of excess expiratory positive pressure by the modality known as Cflex during Continuous Positive Airway Pressure therapy (CPAPFlex) has been suggested to improve comfort without compromising efficacy. We will compare CPAP to CPAPFlex in subjects with OSA. STUDY DESIGN: Subjects with new onset habitual snoring will be screened for OSA using home sleep studies and rhinomanometry will be used to determine nasal resistance. In 400 subjects with OSA we will perform a randomized double blind cross-over study comparing CPAP to CPAPflex, and relate nasal resistance to adherence to CPAP therapy. DISCUSSION: This is the first multicenter trial designed to test the hypothesis that adherence to CPAP therapy relates to nasal resistance and CPAPFlex will improve adherence to CPAP in those subjects with high nasal resistance. We anticipate the following results from this trial: 1. Increased nasal resistance is associated with decreased adherence to CPAP therapy. 2. Use of CPAPFlex improves adherence with CPAP therapy in subjects with high nasal resistance, but not in those with low nasal resistance. 3. The benefit of CPAPFlex on adherence is greatest when offered at CPAP therapy initiation rather than as a "rescue" therapy in subjects with high nasal resistance. TRIAL REGISTRATION: ClinicalTrials.gov Identifier: NCT01753999 , Date: 12 December 2012.

BACKGROUND: This paper addresses the problem of detecting sleep spindles and K-complexes in human sleep EEG. Sleep spindles and K-complexes aid in classifying stage 2 NREM human sleep. NEW METHOD: We propose a non-linear model for the EEG, consisting of a transient, low-frequency, and an oscillatory component. The transient component captures the non-oscillatory transients in the EEG. The oscillatory component admits a sparse time-frequency representation. Using a convex objective function, this paper presents a fast non-linear optimization algorithm to estimate the components in the proposed signal model. The low-frequency and oscillatory components are used to detect K-complexes and sleep spindles respectively. RESULTS AND COMPARISON WITH OTHER METHODS: The performance of the proposed method is evaluated using an online EEG database. The F1 scores for the spindle detection averaged 0.70 +/- 0.03 and the F1 scores for the K-complex detection averaged 0.57 +/- 0.02. The Matthews Correlation Coefficient and Cohen's Kappa values were in a range similar to the F1 scores for both the sleep spindle and K-complex detection. The F1 scores for the proposed method are higher than existing detection algorithms. CONCLUSIONS: Comparable run-times and better detection results than traditional detection algorithms suggests that the proposed method is promising for the practical detection of sleep spindles and K-complexes.

Background: Recently, several studies have provided evidence that Abeta dynamics are influenced by the sleep-wake cycle. In transgenic mice, soluble Abeta levels are higher in the interstitial space during wakefulness and lower during sleep, while sleep deprivation increases Abeta concentrations and accelerates Abeta plaque deposition. In humans, in a study where serial cerebrospinal fluid (CSF) samples were collected for 36 hours, Abeta42 concentrations fluctuated with a diurnal pattern, with the lowest Abeta42 levels in the morning sampling. This CSF Abeta diurnal pattern has been related to higher synaptic activity during wakefulness and decreased synaptic activity during slow wave sleep (SWS). In the elderly, brain soluble Abeta42 levels may be relatively increased as a result of: a) agedependent loss of SWS; and, b) sleep disturbances common in late-life that disrupt SWS. The present study examined whether SWS was associated with CSF Abeta42 levels in a morning lumbar puncture (LP) performed between 11:00 AM-01:00 PM. Methods: In a sample of 22 cognitively normal elderly (age 66.5+/-6.7; range 56-83) with available CSF results, we performed a nocturnal polysomnography (NPSG) (average time interval between the NPSG and the LP 12.9+/-10.1 months, range 0-31). 3 subjects had a CSF P-tau/ Abeta42 ratio suggestive of preclinical AD (based on our own dataset of cognitively normal and AD patients modeled to determine the optimal cut-off for diagnostic prediction of AD) and were excluded. Subjects were further divided by median Abeta42 levels (671.95 pg/mL) into High/Low Abeta42. Results: The percent time spent in SWS (%SWS) and absolute SWA were inversely associated with CSF Abeta42 levels (r=-0.70, p<0.01; r=-0.74, p<0.01). There were no associations with the percent time spent in N1, N2 or REM. Results were also significant after controlling for BMI, age, ApoE4 or after including the preclinical AD subjects in the analysis. In group comparisons, normalized SWA in the first cycle was lower in the 'High' Abeta42 group (C3 p<0.05; F4 p <0.1) (Figure 1). Conclusions: In the absence of AD pathology, reduced %SWS or SWA are associated with increases in CSF Abeta42. (Figure Presented)

INTRODUCTION: Inspiratory flow limitation (IFL) is defined as a "flattened shape" of inspiratory airflow contour detected by nasal cannula pressure during sleep and can indicate increased upper airway resistance especially in mild sleep-related breathing disorders (SRBD). The objective of this study was to investigate the association between upper airway abnormalities and IFL in patients with mild SRBD. METHODS: This study was derived from a general population study consisting of selected individuals with apnea-hypopnea index (AHI) below 5 events/h of sleep, ("no obstructive sleep apnea" group) and individuals with AHI between 5 and 15 events/h ("mild obstructive sleep apnea" group). A total of 754 individuals were divided into four groups: group 1: AHI <5/h and <30 % of total sleep time (TST) with IFL (515 individuals), group 2: AHI <5/h and >30 % of TST with IFL (46 individuals), group 3: AHI: 5-15/h and <30 % of TST with IFL (168 individuals), and group 4: AHI: 5-15/h and >30 % of TST with IFL (25 individuals). RESULTS: Individuals with complains of oral breathing demonstrated a risk 2.7-fold larger of being group 4 compared with group 3. Abnormal nasal structure increased the chances of being in group 4 3.2-fold in comparison to group 1. Individuals with voluminous lateral wall demonstrated a risk 4.2-fold larger of being group 4 compared with group 3. CONCLUSION: More than 30 % of TST with IFL detected in sleep studies was associated with nasal and palatal anatomical abnormalities in mild SRBD patients.

OBJECTIVE: To examine whether the presence of sleep-disordered breathing (SDB) is associated with an earlier age at mild cognitive impairment (MCI) or Alzheimer disease (AD)-dementia onset in participants from the Alzheimer's Disease Neuroimaging Initiative (ADNI) cohort. We also examined whether continuous positive airway pressure (CPAP) use is associated with delayed onset of cognitive decline. METHODS: From the ADNI cohort, 3 subsets with progressively stringent criteria were created in a step-wise manner. Age at MCI or AD-dementia onset was the main outcome variable. Analyses were performed separately for each subset in untreated SDB+ vs SDB- and untreated SDB+ vs CPAP+ groups. Chi-square and t tests were performed to examine between-group differences. Survival analyses were performed using the Kaplan-Meier method, compared by the log-rank test, and assessed by multivariate Cox regression adjusting for potential confounders. RESULTS: SDB+ patients had a younger age at MCI onset in all subsets (MC1: 72.63 vs 83.67; MC2: 72.15 vs 83.45; MC3: 77.40 vs 89.89; p < 0.01). SDB+ patients had a younger age at AD-dementia onset only in our most conservative subset (AC3: 83.46 vs 88.13; p < 0.05). In a combined outcome analysis, SDB+ patients had a younger age at onset to MCI or AD-dementia in all subsets. In subsets 1 and 2, CPAP use delayed the age at MCI onset (CMC1: 72.63 vs 82.10; CMC2: 72.11 vs 82.10; p < 0.01). CONCLUSIONS: Consistent with our hypothesis, the presence of SDB was associated with an earlier age at cognitive decline. Our findings in CPAP+ participants suggest that CPAP treatment of SDB may delay progression of cognitive impairment.

Introduction: Inspiratory flow limitation (IFL) is defined as a "flattened shape" of the inspiratory airflow contour detected by nasal cannula pressure during sleep and can indicate increased upper airway resistance especially in mild Sleep Related Breathing Disorders (SRBD). The objective of this study was to investigate the association between upper airway abnormalities and IFL in patients with mild SRBD. Methods: This study was derived from a general population study of 1,042 individuals. Were selected individuals without symptoms (with no significant pulmonary disease and no smoking) and with apnea-hypopnea index (AHI) below 5 events/hour of sleep, considered a "normal" group and individuals with symptoms and AHI between 5 and 15 events/hour considered as having mild Obstructive Sleep Apnea Syndrome (OSAS). 754 individuals were divided into 4 groups: group 1: AHI < 5/hour and < 30% of total sleep time (TST) with IFL (515 individuals), group 2: AHI < 5/hour and > 30% of TST with IFL (46 individuals), group 3: AHI: 5-15/hour and < 30% of TST with IFL (168 individuals) and group 4: AHI: 5-15/hour and > 30% of TST with IFL (25 individuals). Results: Individuals with complains of oral breathing demonstrated chance 2.7 folds larger of having mild OSAS with > 30% TST with IFL compared to mild OSAS with < 30%) of TST with IFL. Abnormal nasal structure increased chances of having mild OSAS with IFL > 30% 3.2 folds in comparison to normal with < 30% of TST with IFL. Those ones that had voluminous lateral wall demonstrated chance 4.2 folds larger of having mild OSAS with > 30% of TST with IFL compared to mild OSAS with < 30% of TST with IFL. Conclusion: More than 30% of TST with IFL detected in polysomnography was associated with nasal and palatal anatomical abnormalities in mild SRBD patients. IFL may be an additional parameter for evaluating upper airway obstruction in mild OSAS patients

Introduction: In cognitively normal elderly, short sleep duration is associated with deficits in cognitive performance while physical activity has shown to be protective and improve cognitive function. Actigraph monitoring systems are used to objectively assess sleep but also capture measures of physical activity during the daytime. The purpose of this study is to determine whether daytime activity and sleep duration have independent effects on cognition in normal elderly. Methods: 44 community dwelling cognitively normal (Clinical Dementia Rating = 0) elderly (Age 66.2 +/- 7.3, Gender (36.4%Male, 63.6% Female), non-depressed (Geriatric Depression Scale < 7) participants wore an actigraph (Octagonal Basic Motionlogger, Ambulatory Monitoring Inc, NY) for 7 consecutive days. Data were analyzed in the zero crossing mode for total sleep duration (TST), and mean daytime activity using the provided automated algorithm. All subjects underwent a standard neuropsychological test battery with subscales assessing immediate and delayed recall of orally presented paragraphs and verbal paired associates, digit span (backward and forward), and executive function (trail making test B [TMTB]). Results: Daytime Activity and TST were not correlated with each other. Short sleep duration was associated with longer completion times in the TMTB (r = -0.3, p < 0.05) while Daytime Activity was associated with better performance in verbal paired associates (r = 0.4, p < 0.01) and digit span backward (r = 0.4, p < 0.01). Daytime Activity and TST showed additive effects on verbal paired associates (Daytime Activity F change = 5.95, p < 0.05 and TST F change = 3.18, p < 0.1). Conclusion: Daytime Activity had a significant effect on cognition independent of sleep duration. While these preliminary findings should be interpreted with caution due to small sample size, our data suggest that in studies examining cognition in elderly subjects, actigraphic data should be analyzed for daytime activity in addition to sleep duration