Presentation attacks are falsified biometric traits presented on biometric systems to deceive them. While biometric systems can be tuned and modified to reliably detect known presentation attacks, their performance significantly degrades when encountering unknown presentation attacks. Here, we propose a new approach toward detecting unknown presentation attacks based on the measurement and characterization of synchrony between multiple physiological signals obtained from contact and contactless sensors. Synchrony between two physiological signals was captured by analyzing the blood flow dynamics and respiration patterns. The instantaneous phase difference between two physiological signals was represented as a phase vector using the Hilbert transform and the degree of phase coherence defined as the absolute mean of phase vectors over the analysis period was used as a measure of synchrony. A weighted k-nearest neighbors classifier was then designed to detect valid and invalid biometric presentations based on the degree of phase coherence. The proposed method was validated on the detection of synchrony between two respiration patterns obtained through the measurement of chest movements using an ultra-wideband radar and respiratory sinus arrhythmia using a finger photoplethysmogram sensor on data collected from 50 individuals. It achieved a high accuracy of 95.3%, sensitivity of 96%, and specificity of 94% in detecting corrupted and nonsynchronous patterns that did not contain valid respiration signatures. The proposed method shows promise toward improving the reliability of biometric systems in the detection of unknown and sophisticated attacks that may spoof one or more of the presented biometrics.
Fiona C Baker
SRI Author
Performance of Fitbit Charge 3 Against Polysomnography in Measuring Sleep in Adolescent Boys and Girls
We evaluated the performance of Fitbit Charge 3™ (FC3), a multi-sensor commercial sleep-tracker, for measuring sleep in adolescents against gold-standard laboratory polysomnography (PSG). Single-night PSG and FC3 sleep outcomes were compared in thirty-nine adolescents (22 girls; 16-19 years), 12 of whom presented with clinical/subclinical DSM-5 insomnia symptoms (7 girls). Discrepancy analysis, Bland-Altman plots, and epoch-by-epoch analyses were used to evaluate FC3 performance. The influence of several factors potentially affecting FC3 performance (e.g., sex, age, body mass index, firmware version, and magnitude of heart rate changes between consecutive PSG epochs) was also tested. In the sample of healthy adolescents, FC3 systematically underestimated PSG total sleep time by about 11 min and sleep efficiency by 2.5%, and overestimated wake after sleep onset by 9 min. Proportional biases were detected for “light” and “deep” sleep duration, resulting in significant underestimation of these parameters for those participants having longer PSG N1+ N2 and N3 durations, respectively. No significant systematic bias was detected for sleep efficiency and sleep onset latency. Epoch-by-epoch analysis showed sleep-stage sensitivity (average proportion of PSG epochs correctly classified by the device for a given sleep stage) of 68% for wake, 78% for “light” sleep, 59% for “deep” sleep, and 69% for rapid eye movement (REM) sleep in healthy sleepers. Similar results were found in the sample of adolescents with insomnia symptoms. Body mass index was positively associated with FC3-PSG discrepancies in wake after sleep onset (R 2 = .16, p = .048). The magnitude of the heart rate acceleration/deceleration between consecutive PSG epochs was an important factor affecting FC3 classifications of sleep stages. Our results are in line with a general trend in the literature, suggesting better performance for the recently introduced multi-sensor devices compared to motion-only devices, although further developments are needed to improve accuracy in sleep stage classification and wake detection. Further insight is needed to determine factors potentially affecting device performance, such as accuracy and reliability (consistency of performance over time), in different samples and conditions.
Physiological Responses to Acute Psychosocial Stress in Women with Menopausal Insomnia
Introduction: Insomnia disorder is a common sleep disorder and frequently emerges in the context of menopause, being associated with menopause-specific factors such as hot flashes and other psychosocial variables. Increased vulnerability to stress may also contribute to the development of insomnia in midlife women. Here, we aimed to investigate whether there are differences in physiological reactivity to acute psychosocial stress in women with menopausal insomnia compared with controls.
Methods: We investigated cortisol and heart rate [HR] responses to an acute experimental psychosocial stress (Trier Social Stress Test, TSST) approximately 1 h after waking in the morning in midlife women with ( n = 22) and without ( n = 16) DSM-IV insomnia disorder (Age: 50.05 ± 3.10 years), developed in the context of menopause.
Results: Despite similar perceived stress levels, women with insomnia showed blunted HR increases (~29% HR acceleration) to the TSST compared to controls (~44% HR acceleration) ( p = 0.026). No group differences in HR were detected at baseline or during post-task recovery. Cortisol stress responses were inconclusive, with most of the women (60%) failing to exhibit significant cortisol increases in response to the TSST. A greater magnitude of the cortisol awakening response (CAR) predicted the likelihood of being a non-responder ( p = 0.036), showing the confounding effect of CAR on cortisol stress responses.
Discussion: Women with menopausal insomnia show blunted cardiac responses to stress, suggesting alterations in the autonomic reactivity to acute stress. Whether these alterations are pre-existing or are a consequence of insomnia, needs to be determined.
Sleep and Circadian Regulation of the Autonomic Nervous System
Sleep and the autonomic nervous system (ANS) are intimately connected. The ANS is under the influence of circadian and sleep-dependent modulation. Forced desynchrony and constant routine protocols indicate strong circadian influences on heart rate (HR) and cardiac vagal activity, which fluctuate across 24 hours, with HR being lower, and vagal activity higher, during the nocturnal period. Sleep also influences ANS activity: during non-rapid-eye-movement (NREM) sleep, sympathetic activity is lower and vagal functioning is higher, compared to rapid-eye-movement (REM) sleep, where ANS activity is more similar to wakefulness. A change in ANS innervation of the heart and vasculature drives the wake-to-sleep reductions in blood pressure, HR, and systemic vascular resistance. The reduction in cardiovascular activity during sleep, prominent during NREM sleep, plays a key role in maintaining cardiovascular health, providing a “ cardiovascular holiday. ” Sleep-dependent as well as circadian regulation of vagal activity is evident very early in life and persists across adulthood. There is some evidence of sex differences in sleep-dependent vagal activity in adolescents as well as female hormone effects on nocturnal ANS measures, although further work is needed to determine the significance of these effects.
How the COVID‐19 Pandemic Has Changed Our Lives: A Study of Psychological Correlates Across 59 Countries
Objective: This study examined the impact of the COVID‐19 pandemic and subsequent social restrictions or quarantines on the mental health of the global adult population.
Method: A sample of 6,882 individuals ( M age = 42.30; 78.8% female) from 59 countries completed an online survey asking about several pandemic‐related changes in life and psychological status.
Results: Of these participants, 25.4% and 19.5% reported moderate‐to‐severe depression (DASS‐21) and anxiety symptoms (GAD‐7), respectively. Demographic characteristics (e.g. higher‐income country), COVID‐19 exposure (e.g., having had unconfirmed COVID‐19 symptoms), government‐imposed quarantine level, and COVID‐19‐based life changes (e.g., having a hard time transitioning to working from home; increase in verbal arguments or conflict with other adult in home) explained 17.9% of the variance in depression and 21.5% in anxiety symptoms.
Conclusions: In addition to posing a high risk to physical health, the COVID‐19 pandemic has robustly affected global mental health, so it is essential to ensure that mental health services reach individuals showing pandemic‐related depression and anxiety symptoms.
Effects of forehead cooling and supportive care on menopause-related sleep difficulties, hot flashes and menopausal symptoms: A pilot study.
Objective/Background: This pilot study explored the efficacy of a novel forehead cooling device for perceived sleep difficulties and hot flashes in menopausal-age women.
Participants: 20 women (55.1 ± 4.2 years; 19 post-menopausal) with insomnia symptoms and self-reported two or more hot flashes per day.
Methods: Participants completed daily assessments of sleep and hot flashes (via diaries) across 1 baseline week and 4 weeks of open-label, in-home, nightly treatment with a forehead cooling device (15–18°C) along with sleep hygiene instructions. They also completed ratings of insomnia and menopausal symptoms using standardized questionnaires.
Results: Women reported reductions in sleep onset latency (SOL), wakefulness after sleep onset (WASO), and nocturnal hot flash severity during the first week of treatment (SOL: 25.7 ± 18.4 min; WASO: 36.3 ± 27.3 min; hot flash severity: 3.0 ± 2.8) compared with baseline (SOL: 38 ± 26.3 min; WASO: 52.2 ± 35.6 min; hot flash severity: 6.8 ± 3.7), with further improvements after 2–4 weeks of use ( p < .001). There were also clinically meaningful reductions in insomnia severity and hot flash-related daily interference and lower psychological and physical symptom scores on the Greene climacteric scale after treatment (all p’s<0.001). Conclusions: This exploratory, naturalistic, pilot study shows that nightly use of a forehead cooling device produces improvements in self-reported sleep and reductions in insomnia, hot flash, and other menopausal, symptoms. Controlled studies are warranted to determine the role of this therapy in the management of sleep difficulties and menopausal symptoms in women. Further mechanistic studies are needed to understand the physiological impact of forehead cooling on sleep and menopausal symptoms.
A standardized framework for testing the performance of sleep-tracking technology: Step-by-step guidelines and open-source code
Sleep-tracking devices, particularly within the consumer sleep technology (CST) space, are increasingly used in both research and clinical settings, providing new opportunities for large-scale data collection in highly ecological conditions. Due to the fast pace of the CST industry combined with the lack of a standardized framework to evaluate the performance of sleep trackers, their accuracy and reliability in measuring sleep remains largely unknown. Here, we provide a step-by-step analytical framework for evaluating the performance of sleep trackers (including standard actigraphy), as compared to gold-standard polysomnography (PSG) or other reference methods. The analytical guidelines are based on recent recommendations for evaluating and using CST from our group and others (de Zambotti, Cellini, Goldstone, Colrain & Baker, 2019; Depner et al., 2019), and include raw data organization as well as critical analytical procedures, including discrepancy analysis, Bland-Altman plots, and epoch-by-epoch analysis. Analytical steps are accompanied by open-source R functions (depicted at https://sri-human-sleep.github.io/sleep-trackers-performance/AnalyticalPipeline_v1.0.0.html). In addition, an empirical sample dataset is used to describe and discuss the main outcomes of the proposed pipeline. The guidelines and the accompanying functions are aimed at standardizing the testing of CSTs performance, to not only increase the replicability of validation studies, but also to provide ready-to-use tools to researchers and clinicians. All in all, this work can help to increase the efficiency, interpretation, and quality of validation studies, and to improve the informed adoption of CST in research and clinical settings.
Stress, Sleep, and Autonomic Function in Healthy Adolescent Girls and Boys: Findings from the NCANDA Study
Objectives : Starting in adolescence, female sex is a strong risk factor for the development of insomnia. Reasons for this are unclear but could involve altered stress reactivity and/or autonomic nervous system (ANS) dysregulation, which are strongly associated with the pathophysiology of insomnia. We investigated sex differences in the effect of stress on sleep and ANS activity in adolescents, using the first night in the laboratory as an experimental sleep-related stressor.
Design : Repeated measures (first night vs. a subsequent night) with age (older/younger) and sex (males/females) as between factors.
Setting: Recordings were performed at the human sleep laboratory at SRI International.
Participants : One hundred six healthy adolescents (Age, mean ± SD: 15.2 ± 2.0 years; 57 boys).
Measures: Polysomnographic sleep, nocturnal heart rate (HR), and frequency-domain spectral ANS HR variability (HRV) indices.
Results : Boys and girls showed a first-night effect, characterized by lower sleep efficiency, lower %N1 and %N2 sleep, more wake after sleep onset and %N3 sleep, altered sleep microstructure (increased high-frequency sigma and Beta1 electroencephalographic activity), and reduced vagal activity ( P < .05) on the first laboratory night compared to a subsequent night. The first night ANS stress effect (increases in HR and suppression in vagal HRV during rapid eye movement sleep) was greater in girls than boys P < .05). Conclusions: Sleep and ANS activity were altered during the first laboratory night in adolescents, with girls exhibiting greater ANS alterations than boys. Findings suggest that girls may be more vulnerable than boys to sleep-specific stressors, which could contribute to their increased risk for developing stress-related sleep disturbances.
Impact of evening alcohol consumption on nocturnal autonomic and cardiovascular function in adult men and women: A dose–response laboratory investigation
Study Objectives: To investigate the dose-dependent impact of moderate alcohol intake on sleep-related cardiovascular (CV) function, in adult men and women.
Methods: A total of 26 healthy adults (30–60 years; 11 women) underwent 3 nights of laboratory polysomnographic (PSG) recordings in which different doses of alcohol (low: 1 standard drink for women and 2 drinks for men; high: 3 standard drinks for women and 4 drinks for men; placebo: no alcohol) were administered in counterbalanced order before bedtime. These led to bedtime average breath alcohol levels of up to 0.02% for the low doses and around 0.05% for the high doses. Autonomic and CV function were evaluated using electrocardiography, impedance cardiography, and beat-to-beat blood pressure monitoring.
Results: Presleep alcohol ingestion resulted in an overall increase in nocturnal heart rate (HR), suppressed total and high-frequency (vagal) HR variability, reduced baroreflex sensitivity, and increased sympathetic activity, with effects pronounced after high-dose alcohol ingestion (p’s < 0.05); these changes followed different dose- and measure-dependent nocturnal patterns in men and women. Systolic blood pressure showed greater increases during the morning hours of the high-alcohol dose night compared to the low-alcohol dose night and placebo, in women only (p’s < 0.05).
Conclusions: Acute evening alcohol consumption, even at moderate doses, has marked dose- and time-dependent effects on sleep CV regulation in adult men and women. Further studies are needed to evaluate the potential CV risk of repeated alcohol-related alterations in nighttime CV restoration in healthy individuals and in those at high risk for CV diseases, considering sex and alcohol dose and time effects.
