Publications

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Performance of a New Portable Wireless Sleep Monitor
Journal of Clinical Sleep Medicine, Vol. 13, No. 2, 2017
We show that EEG signals generated by this monitor are visually indistinguishable from polysomnography signals and, when scored with its automatic system that requires minimal guided editing, produce results in good agreement with manual scoring, and, in addition, provides a continuous index of sleep depth throughout the night (Odds-Ratio-Product). This monitor may make it possible to obtain high quality inexpensive sleep evaluation in the home.
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Minimizing Interrater Variability in Staging Sleep by Use of Computer-Derived Features
J Clin Sleep Med 2016;12(10):1347–1356
Percent agreement between scorers improved dramatically after their scores were independently modified using digitally obtained information about sleep depth, delta duration, spindles, and K complexes. Provision of such information during scoring can greatly reduce interrater variability in sleep staging by eliminating the guesswork in scoring epochs with equivocal features.
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Odds Ratio Product of Sleep EEG as a Continuous Measure of Sleep State
SLEEP 2015;38(4):641–654
Power spectrum of EEG was determined in 3-second epochs and divided into delta, theta, alpha-sigma, and beta frequency bands. The range of powers in each band was divided into 10 aliquots. EEG patterns were assigned a 4-digit number that reflects the relative power in the 4 frequency ranges (10,000 possible patterns). Probability of each pattern occurring in 30-s epochs staged awake was determined, resulting in a continuous probability value from 0% to 100%. This was divided by 40 (% of epochs staged awake) producing the odds ratio product (ORP), with a range of 0–2.5. In validation testing, average ORP decreased progressively as EEG progressed from wakefulness to stage N3. ORP < 1.0 predicted sleep and ORP > 2.0 predicted wakefulness in > 95% of 30-s epochs. There was an excellent correlation between ORP in current 30-s epochs and the likelihood of arousal or awakening occurring in the next 30-s epoch. The results support the use of the odds ratio product (ORP) as a continuous measure of sleep depth.
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The case for using digital EEG analysis in clinical sleep medicine (Review)
Sleep Science and Practice (2017) 1:2
Evaluation of sleep in clinical polysomnograms continues to rely almost exclusively on visual scoring that implements rules proposed by Rechtschaffen and Kales nearly 50 years ago. Apart from its cost and time consuming nature, visual scoring has limitations including: A) Sleep depth, which is a continuous variable, is treated as if it changes in a stepwise fashion from light (stage 1), to intermediate (stage 2) to deep (stage 3). B) Even with this limited scale, there is considerable inter-scorer variability, particularly in scoring stages 1 and 3 of non-REM sleep, thereby adding uncertainty to %time spent in these stages as a reliable metric for evaluating sleep depth. C) Limitation in scoring some of EEG features, including 1) arousal intensity, 2) extent of Alpha intrusion and 3) frequency, and characteristics of sleep spindles and K complexes. Digital analysis can solve these problems but producing a reliable system has been a challenge. In this review I begin with recent advances in digital scoring of sleep according to the Rechtschaffen and Kales rules and conclude that this technology has progressed enough to make it possible to obtain reliable, reproducible scoring, comparable in accuracy to scoring by highly experienced technologists, with minimal editing. This is followed by description of several new metrics that can be obtained if digital scoring systems were to be used routinely in clinical studies. The scientific evidence supporting the potential of these metrics to positively impact sleep medicine.
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Accuracy of Automatic Polysomnography Scoring Using Frontal Electrodes
J Clin Sleep Med. 2016 May 15;12(5):735-46.
The research demonstrated that using a computer assisted digital sleep scoring program, frontal electrodes gave comparable results to using central electrodes. This makes it possible to obtain reliable scoring from frontal electrodes, which can be easily applied by the patient at home, thereby making it less complicated and expensive to obtain information about sleep in home studies. 

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Agreement in Computer-Assisted Manual Scoring of Polysomnograms across Sleep Centers
Sleep. 2013 Apr 1;36(4):583-9
A standard set PSG files from a cohort of middle-aged females with sleep breathing disorders were manually scored by experienced technicians from five major sleep centres (including University of Pennsylvania. Stanford University, Harvard University) using their preferred software (e.g.). Three definitions of hypopneas were used including the recommended definition by the American Association of Sleep Medicine (AASM). The study found that although scoring was consistent within centres and between centres for the standard AASM definition of a hypopnea, as the definition for a hypopnea became less familiar (as is often the case when researching non-standardized markers), the results became less consistent. 

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Arousal Responses during Overnight Polysomnography and their Reproducibility in Healthy Young Adults
A novel scale for arousal intensity was used to correlate the magnitude of an arousal with the concomitant maximal change in the heart rate (HR) in healthy young adults. It was found that although the slope of the regression plot between arousal intensity and change in HR varied substantially between individuals. For a given individual there was a strong correlation between their arousal intensity score and their maximal change in HR after the arousal that was reproducible in multi-night studies.

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Heritability of Heart Rate Response to Arousals in Twins
Sleep. 2017
This study builds off the earlier publication (Arousal Responses during Overnight Polysomnography and their Reproducibility in Healthy Young Adults) by studying the effect of arousal intensity on heart rate variability in a cohort of otherwise normal and healthy identical and fraternal twins. The study showed that underlying genetic factors significantly influence arousals and the heart rate response to arousals during sleep. These results add further evidence that many sleep characteristics are heritable and therefore influenced by underlying genetic factors. These results suggest that outcomes related to arousals associated with sleep disorders (e.g., daytime sleepiness and cardiovascular morbidities) may be heritable.

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Immediate postarousal sleep dynamics: an important determinant of sleep stability in obstructive sleep apnea
J Appl Physiol (1985). 2016 Apr 1;120(7):801-8
How easily one is aroused from sleep has significant health implications for OSA, insomnia and the overall benefit of restorative sleep. This is the first paper to introduce the concept of ORP-9 which is the ORP score 9 seconds after an arousal. It serves as a numerical measure of how quickly an individual can return to deep sleep after an arousal. Individuals with a high ORP-9 score tend to require a longer time to return to sleep and are highly susceptible to additional interruptions when compared to individuals with a low ORP-9. In OSA patients, ORP-9 correlated very strongly with both arousal/awakening and the apnea-hypopnea index suggesting it could be a useful measure to quantify sleep stability.

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Performance of an Automated Polysomnography Scoring System Versus Computer-Assisted Manual Scoring
Sleep. 2013 Apr 1;36(4):573-82
In this study, two technologists at 5 different laboratories manually scored a standard set of PSGs for sleep stages, arousals and AHI and then compared the results to those generated by a fully automated scoring software system.  The intraclass correlation coefficient (ICC) was 0.8 for many sleep measures between manual and automatic scoring and greater than 0.9 for the AHI score, suggesting automated scoring yielded similar results as manual scoring within accepted tolerances. Use of automated scoring could help standardize PSG scoring between sites thereby improving efficiencies and facilitating research.

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Utility of Technologist Editing of Polysomnography Scoring Performed by a Validated Automatic System
Ann Am Thorac Soc. 2015 Aug;12(8):1206-18
In this study, the time taken to edit a polysomnography (PSG) file manually, after automated scoring with and without editing (using a built-in editor helper function) was compared. Although high intraclass correlation coeffecients (ICCs) were obtained between manual scoring and automated scoring alone, when the editor helper was used, scoring time reduced from approximately 54-59 minutes to 6 minutes and the ICC exceeded 0.9 for all variables, excluding sleep onset latency (0.88), N3 (0.74) and N1 (0.75). The study suggests efficiencies in scoring time can be obtained using automated scoring with a short time manually editing a scored PSG file with the editor helper function, without sacrificing the veracity of the clinical interpretation of the PSG file.

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Relationship between arousal intensity and heart rate response to arousal
SLEEP. 2014;37:645-653
Arousals are currently scored as an “all or nothing” event by the American Academy of Sleep Medicine criteria. However, potentially valuable information about the intensity of an arousal is lost with this binary methodology. In this paper an automated algorithm was developed to scale the arousal intensity using changes in wavelet features. There was a strong correlation between arousal scale and the change in heart rate variability within each subject although the slope of the relationship varied among subjects. The clinical importance of the arousal intensity and the associated arousal-related tachycardia invite further examination.
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Staging Sleep in Polysomnograms: Analysis of Inter-Scorer Variability
J Clin Sleep Med. 2016;12:885-94
Inter-scorer variability even between highly qualified technologists in scoring polysomnograms is a well-recognized problem, that impacts the diagnosis and management of sleep disorders and confounds interpretation of outcome studies. An analysis of the reasons for the variability traced back to the presence of a large number of equivocal epochs that can legitimately be assigned any of two, or even three, sleep stages by competent technologists. These findings suggest that digital identification of key staging variables (e.g., spindles, delta wave duration, objective sleep depth) is needed if inter-scorer variability is to be minimized and that better training or fine-tuning of the scoring guidelines are not likely to be effective.
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Web-based vs telehealth-based delivery of CBT-I: A randomized controlled trial
Holmqvist, M., Vincent, N., & Walsh, K. (2013). Sleep Medicine, 15, 187-195.
The purpose of our study was to evaluate and compare two methods of service delivery (web-based and telehealth-based) for chronic insomnia with regard to patient preference, clinical effectiveness, and patient satisfaction.
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Attrition and Adherence in the Online Treatment of Chronic Insomnia
Hebert, E., Vincent, N., Lewycky, S., & Walsh, K. (2010). Behavioral Sleep Medicine, 8, 141-150
This study examined the ability of the Theory of Planned Behavior (TPB; Ajzen, 1985) and the Transtheoretical Model of Behavior Change (TTM; Prochaska & DiClemente, 1983) to explain adherence and attrition in an online treatment program for chronic insomnia. Responses to questionnaire measures of the TPB and TTM were used to predict adherence and dropout over the subsequent 5 weeks of treatment. Results showed that there was a 17% dropout rate and that perceived behavioral control, social support, and intention to complete the program were significantly associated with adherence to sleep hygiene homework. Attrition was predicted only by symptom severity and psychiatric comorbidity. Implications are that these models should be considered to maximize adherence.
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Logging in for Better Sleep: A randomized controlled trial of the effectiveness of online treatment for chronic insomnia
Vincent, N., & Lewycky, S. (2009). Sleep, 32, 807-815
Despite effective cognitive behavioral treatments for chronic insomnia, such treatments are underutilized. This study evaluated the impact of a 5-week, online treatment for insomnia.
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Dissemination of an Internet-Based Treatment for Chronic Insomnia Into Primary Care
Beaulac, J., Vincent, N., & Walsh, K. (2014). Behavioral Sleep Medicine,12, 1–16
This study evaluated the effectiveness of two strategies (provider-targeted, consumer-targeted) in the dissemination of an insomnia treatment into primary care. Results of the study indicated that more patients from the provider-targeted, than the consumer-targeted, clinic followed up on the referral for insomnia treatment, but that overall there was limited uptake. These results did not seem to be associated with low levels of provider interest, although providers expressed need for more education about the insomnia program. Implications of these results are that future research efforts would benefit from expanding upon the education of providers in terms of treatment offered, perhaps teaching providers how to better motivate their patients for behavior change.
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Determinants of success for computerized CBT: Examination of an insomnia program.
Vincent, N., Walsh, K., & Lewycky, S. (2013). Behavioral Sleep Medicine, 11, 1-13.
This study evaluated plausible moderators of outcome in a 6-week computerized treatment for insomnia. Using secondary data from two randomized controlled trials, participants were 228 adults with chronic insomnia. Participants received computerized treatment from their homes. Outcomes were assessed using a sleep diary, as well as several standardized self-report scales. Using linear mixed models with SPSS, treatment was largely robust to comorbid conditions, education, age, and gender. Results showed that psychiatric comorbidity and education moderated the impact of treatment on fatigue and that sleep symptom comorbidity moderated the impact of treatment on maladaptive attitudes about sleep. Implications of these findings are that more widespread use of computerized treatment for insomnia may be warranted. (Clinical Trials.gov Identification #: NCT00821041.)
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Reliability of the AASM Rules for Assessing Sleep Depth in Clinical Practice
Journal of Clinical Sleep Medicine, Vol. 14, No. 2
The American Academy of Sleep Medicine has published manuals for scoring polysomnograms that recommend time spent in non-rapid eye movement sleep stages (stage N1, N2, and N3 sleep) be reported. Given the well-established large interrater variability in scoring stage N1 and N3 sleep, we determined the range of time in stage N1 and N3 sleep scored by a large number of technologists when compared to reasonably estimated true values.
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