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June 2001 - March 2021
June 1996 - March 2021
Education
September 1993 - June 1999
September 1989 - June 1993
Publications
Publications (269)
The recent article by Chang et al. (1) adds to the growing literature that exposure to even seemingly dim light at night can have a negative impact on sleep. There have been several articles published in recent years indicating that the seemingly innocuous light emitted from consumer electronics devices has the capacity to increase alertness at nig...
Beyond image-forming (IF) effects, light can evoke changes in subcortical functions including circadian timing and sleep drive. Non-image forming (NIF) functions of light are subserved by a network of rods, cones, and intrinsically photosensitive retinal ganglion cells. The physiology of NIF photoreception remains incompletely understood. NIF funct...
The human circadian timing system is most sensitive to the phase-shifting effects of light during the biological nighttime, a time at which humans are most typically asleep. The overlap of sleep with peak sensitivity to the phase-shifting effects of light minimizes the effectiveness of using light as a countermeasure to circadian misalignment in hu...
Introduction:
The 'diurnal slope' of salivary cortisol has been used as a measure of stress and circadian function in a variety of reports with several detailing its association with cancer progression. The relationship of this slope, typically a negative value from high morning concentrations to low evening concentrations, to the underlying daily...
To determine if there is a specific pattern of gross motor activity associated with apathy in individuals with Alzheimer disease (AD).
Examination of ad libitum 24-hour ambulatory gross motor activity patterns.
Community-dwelling, outpatient.
Ninety-two individuals with AD, 35 of whom had apathy.
Wrist actigraphy data were collected and examined us...
Background
Objective sleep measures obtained from actigraphy (wrist‐worn accelerometry) reveal sleep disruption patterns and may serve as indicators of neurodegenerative disease. However, whether individuals’ subjective account of their sleep quality corresponds to objective sleep measurements from the previous night is an area little studied. In p...
The duration of sleep data collection from actigraphy is often influenced by practical factors (e.g. workdays versus non‐workdays), but the impact of the variation of duration on outcome measures of interest has not been well explored. This study investigates the effect of the duration of actigraphy measurement on non‐parametric measures of 24‐hr s...
Introduction: Women experience complex physiological and behavioral fluctuations across the menstrual cycle and have a limited understanding of its impact on physical performance. Measurement over a full menstrual cycle (~28 days) poses challenges due to limitations of either in-lab (e.g., time and cost) or remote monitoring (e.g., battery life, me...
Background
Disturbed sleep is frequently identified in adult patients with cancer and their caregivers, with detrimental impact on physical health. Less known is the extent to which self‐reported and actigraph‐measured sleep patterns are similar between patients and their sleep‐partner caregivers, and how these different modes of sleep measurements...
Mental health is independently influenced by the inclination to sleep at specific times (chronotype) and the actual sleep timing (behavior). Chronotype and timing of actual sleep are, however, often misaligned. This study aims to determine how chronotype, sleep timing, and the alignment between the two impact mental health.
In a community-dwelling...
The spectral distribution is a fundamental property of non-monochromatic optical radiation. It is commonly used in research and practical applications when studying how light interacts with matter and living organisms, including humans. In the field of lighting, misconceptions about the spectral distribution of light are responsible for unfounded c...
Introduction
Circadian rest-activity rhythms (RARs), a behavioral manifestation of circadian rhythms, reflect physical activity and sleep patterns over the 24-hour day. With aging, disrupted RARs may be associated with higher cardiometabolic risk, fall risk and cognitive decline. Physical performance also declines with advancing age, leading to dis...
Introduction
The association of insomnia with objective short sleep duration (ISSD) and mortality has not been studied in older persons.
Methods
In 3,601 men from the Osteoporotic Fractures in Men Sleep Study (average age 76±6 years) and 3,295 women from the Study of Osteoporotic Fractures (average age 84±4 years), we used Cox proportional hazards...
Introduction
Circadian rhythms, which control sleep-wake cycles and metabolism, are fundamental to human health. Our study aimed to understand how these rhythms affect proteins in the body throughout the day, and to develop a tool that predicts the body's internal clock phase based on protein expression.
Methods
Plasma samples from 17 healthy adul...
Introduction
Sleep disturbance is frequently identified in patients with cancer and their caregivers, with detrimental impact on physical health. Less known is the extent to which self-reported and actigraphy-derived sleep patterns correlate between patients and their sleep-partner caregivers, and how the two modes of sleep measurements are related...
Obstructive sleep apnea (OSA) is a common, underdiagnosed sleep-related breathing disorder with serious health implications Objective - We propose a deep transfer learning approach for sleep stage classification and sleep apnea (SA) detection using wrist-worn consumer sleep technologies (CST). Methods – Our model is based on a deep convolutional ne...
Background
Sleep-wake regulating circuits are affected during prodromal stages in the pathological progression of both Alzheimer’s disease (AD) and Parkinson’s disease (PD), and this disturbance can be measured passively using wearable devices. Our objective was to determine whether accelerometer-based measures of 24-h activity are associated with...
Introduction
High variability in response and retention rates for posttraumatic stress disorder (PTSD) treatment highlights the need to identify "personalized" or "precision" medicine factors that can inform optimal intervention selection before an individual commences treatment. In secondary analyses from a non-inferiority randomized controlled tr...
Since the 1950’s, polysomnography (PSG) has been the criterion standard for the determination of sleep states. PSG is routinely used in both research and clinical settings to characterize various electrophysiologic phenomena associated with sleep. While there have been substantive advances in the miniaturization of the equipment needed to record PS...
Objective
Cancer can be a traumatic experience affecting multidimensional aspects of sleep among patients and caregivers. This study examined the differential associations of cancer-related post-traumatic stress symptoms (PTSS) with various sleep markers in this population.
Methods
Patients newly diagnosed with colorectal cancer ( n = 138, mean ag...
Background
Disrupted sleep and fragmentation of sleep‐wake rhythms are common in the context of healthy aging as well as in neurodegenerative disease. As wearable devices become increasingly popular among older adults, there is a growing need to understand how metrics of sleep‐wake behavior might be able to identify neurodegenerative disease and di...
Background
There is no consensus on reporting light characteristics in studies investigating non-visual responses to light. This project aimed to develop a reporting checklist for laboratory-based investigations on the impact of light on non-visual physiology.
Methods
A four-step modified Delphi process (three questionnaire-based feedback rounds a...
Objectives: To explore how the blood plasma proteome fluctuates across the 24-hour day and identify a subset of proteins that show endogenous circadian rhythmicity.
Methods: Plasma samples from 17 healthy adults were collected hourly under controlled conditions de- signed to unmask endogenous circadian rhythmicity; in a subset of 8 participants, we...
Collegiate athletes must satisfy the academic obligations common to all undergraduates, but they have the additional structural and social stressors of extensive practice time, competition schedules, and frequent travel away from their home campus. Clearly such stressors can have negative impacts on both their academic and athletic performances as...
Numerous physical and mental health disorders have been linked independently to poor sleep as measured by polysomnography (PSG) and self-reported sleep quality [1]. While potentially representing different aspects of sleep, the association between PSG and self-reported sleep has been extensively studied [2–4]. It has been suggested that a threshold...
Introduction
Isolated REM sleep behavior disorder (iRBD), the loss of motor inhibition during REM sleep, is a symptom of prodromal Lewy body disease, with over 80% of iRBD patients progressing to Parkinson's disease or dementia with Lewy bodies. Disruption of rest-activity patterns, an established predictor of Parkinson's disease, has not been well...
Introduction
A consolidated sleep-wake pattern is essential for maintaining healthy cognition in older individuals, but many suffer from sleep fragmentation that exacerbates age-related cognitive decline and worsens overall mental and physical health. Timed light exposure (light therapy) has been explored as a countermeasure, but mixed results have...
In humans, exposure to continuous light is typically used to change the timing of the circadian clock. This study examines the efficiency of a sequence of light flashes (“flash therapy”) applied during sleep to shift the clock. Healthy participants (n = 10) took part in two 36-h laboratory stays, receiving a placebo (goggles, no light) during one v...
Background. Sleep disturbances are a prominent feature of posttraumatic stress disorder (PTSD), and poorer sleep quality is associated with higher PTSD severity. This highlights the importance of monitoring sleep outcomes alongside PTSD symptoms in treatments targeting PTSD. Yet few studies monitor both sleep and PTSD outcomes, unless sleep is the...
Study objectives:
This study evaluated the effects of early time-restricted eating (eTRE) on shifting the timing of sleep among late sleepers. Primary outcomes included actigraphy- and sleep diary-derived sleep onset, mid-sleep phase, and wake time with total sleep time as a secondary outcome.
Methods:
Fifteen healthy adults with habitual late s...
Purpose:
Circadian rest-Activity Rhythm Disorders (CARDs) are common in patients with cancer, particularly in advanced disease. CARDs are associated with increased symptom burden, poorer quality of life, and shorter survival. Research and reporting practices lack standardization, and formal diagnostic criteria do not exist. This electronic Delphi...
Little is known about links of circadian rhythm alterations with neuropsychiatric symptoms and cognition in memory impaired older adults. Associations of actigraphic rest/activity rhythms (RAR) with depressive symptoms and cognition are examined using function‐on‐scalar regression (FOSR). Forty‐four older adults with memory impairment (mean: 76.84...
Introduction
Non-pharmacological Insomnia Therapies are robustly effective in improving sleep in cognitively intact (CI) older adults. However, it remains unknown whether older adults with mild cognitive impairment (MCI) can engage in insomnia therapy to experience similar sleep improvements.
Methods
We leveraged an existing dataset derived from a...
Introduction
The human circadian clock is synchronized to the outside world through regular ocular light exposure. Light does not need to be continuous to be an effective time cue. Light administered as a sequence of light flashes can be more effective than continuous light of the same illuminance. Exposure to a sequence of light flashes while awak...
Introduction
Both chronotype and the actual timing of sleep have been associated with mental and physical health outcomes. While these often align, life often intervenes and causes a misalignment between desired and actual timing of sleep. The impact of such a misalignment has not been well investigated.
Methods
Community-dwelling (n=73,888) adult...
Sleep-wake regulating circuits are affected during prodromal stages in the pathological progression of both Alzheimer's disease (AD) and Parkinson's disease (PD). Assessment of 24-hour rhythm impairment may serve as an early indicator of disease and cognitive decline. Our objective was to determine whether objective markers of 24-hour activity are...
Controlled breathwork practices have emerged as potential tools for stress management and well-being. Here, we report a remote, randomized, controlled study (NCT05304000) of three different daily 5-min breathwork exercises compared with an equivalent period of mindfulness meditation over 1 month. The breathing conditions are (1) cyclic sighing, whi...
Importance. Human mental and physical health is influenced by both the inclination to sleep at specific times (chronotype) as well as the actual sleep timing (behavior). How the alignment between these impacts mental and physical health has not been well described.
Objective. The goal of this study is to examine the impact of chronotype, actual tim...
Intrinsically photosensitive retinal ganglion cells (ipRGGs) are the most recently discovered photoreceptor class in the human retina. This Element integrates new knowledge and perspectives from visual neuroscience, psychology, sleep science and architecture to discuss how melanopsin-mediated ipRGC functions can be measured and their circuits manip...
Unlike light input for forming images, non-image-forming retinal pathways are optimized to convey information about the total light environment, integrating this information over time and space. In a variety of species, discontinuous light sequences (flashes) can be effective stimuli, notably impacting circadian entrainment. In this study, we exami...
Background
Previous findings indicate important effects of stress, disrupted sleep, and dysregulated circadian rhythms on the progression of cancer. Our understanding of these relationships, however, has been limited by the absence of data from 24-h continuous physiologic monitoring of hormonal and immune activity with simultaneous collection of ob...
The purpose of this study is to characterize the impact of the timing and duration of missing actigraphy data on interdaily stability (IS) and intradaily variability (IV) calculation. The performance of three missing data imputation methods (linear interpolation, mean time of day (ToD), and median ToD imputation) for estimating IV and IS was also t...
Background
Older men with the worse alignment of activity and light may have lower levels of cognition and increased rates of cognitive decline.
Methods
This cohort consisted of 1 036 older men (81.1 ± 4.6 years) from the MrOS Sleep Study (2009–2012). Light and activity levels were gathered by wrist actigraphy. Phasor analysis was used to quantify...
Background
Inadequate sleep is a problem for teens world-wide. Identifying the biological and cultural factors that underlie this phenomenon is dependent on tools that can accurately query sleep-related behaviors. While there are many sleep-related questionnaires available in English, there are a paucity of validated Chinese language versions. As s...
Objective
Test whether Sudarshan Kriya Yoga (SKY) was non-inferior to cognitive processing therapy (CPT) for treating symptoms of post-traumatic stress disorder (PTSD) among veterans via a parallel randomised controlled non-inferiority trial.
Setting
Outpatient Veterans Affairs healthcare centre.
Participants
85 veterans (75 men, 61% white, mean...
Wrist-worn consumer sleep technologies (CST) that contain accelerometers (ACC) and photoplethysmography (PPG) are increasingly common and hold great potential to function as out-of-clinic (OOC) sleep monitoring systems. However, very few validation studies exist because raw data from CSTs are rarely made accessible for external use. We present a de...
Light is the preeminent external influence in determining the position of the internal circadian clock relative to the outside world. In this chapter, we discuss the different parameters of light that impact how it influences the human circadian clock. We detail how the timing (phase), intensity, duration and temporal structure, and spectral compos...
Introduction
Given the increasing use of consumer, wrist-worn devices with triaxial accelerometry (actigraphy), understanding whether 24-hr activity patterns are associated with specific mental and physical health deficits is of paramount importance. The UK Biobank, a community-based sample of adults in the United Kingdom, provides an opportunity t...
Introduction
Isolated REM sleep behavior disorder (iRBD), the loss of motor inhibition during REM sleep, is a symptom of prodromal Lewy body disease, with over 80% of iRBD patients eventually phenoconverting to Parkinson’s disease or Dementia with Lewy bodies. Rest-activity rhythm disruption, also an established predictor of Parkinson’s disease, ha...
Introduction
The measurable aspects of brain function derivable from polysomnography (PSG) that are correlated with sleep satisfaction are poorly understood. Previously, a weak association of PSG measures with subjectively rated sleep depth and restfulness was shown. Using recent developments in automated sleep scoring, which remove the within- and...
Introduction
As individuals age, the circadian-driven timing of their sleep shifts to an earlier hour. Whether such a shift moderates the effectiveness of insomnia treatment on sleep disturbances and mood in older adults is unknown.
Methods
We tested the hypothesis that circadian preference moderates improvements in mood and insomnia symptoms foll...
Introduction
The 24-hour rest and activity behaviors are fundamental human behaviors essential to health and well-being. Functional principal component analysis (fPCA) is a flexible approach for characterizing rest-activity rhythms and does not rely on a priori assumptions about the activity shape. The objective of our study is to apply fPCA to a n...
Introduction
Cognitive-behavioral therapy for insomnia (CBT-I) is an effective multi-component treatment known to improve sleep in older adults with insomnia, including increasing NREM slow-wave activity (SWA) EEG power (0.5 – 4.75Hz) and sleep depth. However, the relative contributions of distinct components of CBT-I to changes in SWA remain unkno...
Introduction
Insomnia is common in older adults with and without mild cognitive impairment (MCI), and is associated with worse neuropsychiatric symptoms (NPS) and impaired daily functioning. Evidence suggests treating insomnia may resolve some of these difficulties in cognitively normal adults. However, little is known about the effects of improvin...
Introduction
Pain worsens insomnia symptoms and increases hyperarousal during sleep. The effectiveness of treatments for improving insomnia symptoms may therefore be affected by co-occurring pain, though this currently remains unknown.
Methods
We tested the hypotheses that (1) higher levels of pain will lead to smaller improvements in subjective a...
Background
Emotion regulation (ER) is a key process underlying posttraumatic stress disorder (PTSD), yet, little is known about how ER changes with PTSD treatment. Understanding these effects may shed light on treatment processes.
Methods
We recently completed a non-inferiority design randomised controlled trial demonstrating that a breathing-base...
Background
The 24-h rest and activity behaviors (i.e., physical activity, sedentary behaviors and sleep) are fundamental human behaviors essential to health and well-being. Functional principal component analysis (fPCA) is a flexible approach for characterizing rest-activity rhythms and does not rely on a priori assumptions about the activity shape...
The melanopsin-containing intrinsically photosensitive retinal ganglion cells (ipRGCs) are characterized by a delayed off-time following the cessation of light stimulation. Here, we exploited this unusual physiologic property to characterize the exquisite sensitivity of the human circadian system to flashed light. In a 34 h in-laboratory between-su...
Light at night can improve alertness and cognition. Exposure to daytime light, however, has yielded less conclusive results. In addition to direct effects, daytime light may also mitigate the impact of nocturnal light exposure on alertness. To examine the impact of daytime lighting on daytime cognitive performance, and evening alertness, we studied...
Study Objectives
The measurable aspects of brain function (polysomnography, PSG) that are correlated with sleep satisfaction are poorly understood. Using recent developments in automated sleep scoring, which remove the within- and between-rater error associated with human scoring, we examine whether PSG measures are associated with sleep satisfacti...
The central pacemaker of flies, rodents, and humans generates less robust circadian output signals across normative aging. It is not well understood how changes in light sensitivity might contribute to this phenomenon. In the present study, we summarize results from an extended data series (n = 5681) showing that the locomotor activity rhythm of ag...
Background
Emotion regulation (ER) is a key process underlying posttraumatic stress disorder (PTSD), yet, little is known about how ER changes with PTSD treatment. Understanding these effects may shed light on treatment processes.
Methods
We recently completed a randomised controlled trial demonstrating that a breathing-based yoga practice (Sudars...
Sleep and activity patterns have been linked to physical performance in older adults. Traditional parametric models of 24-hour activity rhythms fail to adequately capture specific diurnal sleep and wake patterns; functional principal components analysis (fPCA) is a non-parametric approach that addresses this limitation. Using fPCA, we modeled accel...
Background
Bipolar disorder presents with significant phenotypic heterogeneity. The aim of this study was to investigate whether bipolar disorder, type I (BDI) subjects could be meaningfully classified into homogeneous groups according to activity, sleep, and circadian characteristics using latent profile analysis (LPA). We hypothesized that distin...