Steven A. Shea

Oregon Health and Science University | OHSU · Oregon Institute of Occupational Health Sciences

An infinite number of possible combinations of tidal volume and breathing frequency, as well as pattern of airflow, can achieve the alveolar ventilation required for normal gas exchange. Individuals appear to select one particular pattern. This paper summarises our work relating to differences in the pattern of breathing between individuals when at...

This review has described the many behavioural and arousal-related influences on breathing and the extent of these influences in humans. The chief examples have included the effect on breathing of altered mental activity, wakefulness and sleep, and learned respiratory responses. Determining the precise neurological mechanisms underlying these effec...

In healthy humans ventilatory chemoreception results in exquisite regulation of arterial blood gases during NREM sleep, but during wakefulness other behavioral and arousal-related influences on breathing compete with chemoreceptive respiratory control. This paper examines the extent of chemoreceptive control of breathing within the normal physiolog...

Genioglossal muscle (GG) activity is modulated by both chemoreceptive and mechanoreceptive reflexes that help stabilize airway patency. We assessed the effects of blood gas changes, within the range encountered during mild obstructive apnea-arousal cycles, on GG activity and the GG reflex to upper airway negative pressure. Eighteen healthy adults w...

• Upper airway dilator muscles are phasically activated throughout breathing by respiratory pattern generator neurons. Studies have shown that non-physiological upper airway mechanoreceptive stimuli (e.g. rapidly imposed pulses of negative pressure) also activate these muscles. Such reflexes may become activated during conditions that alter airway...

Physiological function fluctuates across 24 h due to ongoing daily patterns of behaviors and environmental changes, including the sleep/wake, rest/activity, light/dark, and daily temperature cycles. The internal circadian system prepares the body for these anticipated behavioral and environmental changes, helping to orchestrate optimal cardiovascul...

Introduction Obesity and cardiovascular disease are commonplace in industrialized societies, particularly in nightshift workers. To investigate whether a shift in the circadian timing of energy intake or an increase in sleep variability may be mechanisms for adverse cardiometabolic health, we leveraged a natural experiment that occurs in newly-hire...

Over 50,000 children are hospitalized annually for traumatic brain injury (TBI) and face long-term cognitive morbidity. Over 50% develop sleep/wake disturbances (SWDs) that can affect brain development and healing. We hypothesized SWDs would portend worse executive function outcomes in children aged 3–18 years with TBI 1–3 months after hospital dis...

Spontaneous synchronization over large networks is ubiquitous in nature, ranging from inanimate to biological systems. In the human brain, neuronal synchronization and de-synchronization occur during sleep, with the greatest degree of neuronal synchronization during slow wave sleep (SWS). The current sleep classification schema is based on electroe...

Night work increases diabetes risk. Misalignment between the central circadian “clock” and daily behaviors, typical in night workers, impairs glucose tolerance, likely due to internal misalignment between central and peripheral circadian rhythms. Whether appropriate circadian alignment of eating can prevent internal circadian misalignment and gluco...

Sudden cardiac death (SCD), the unexpected death due to acquired or genetic cardiovascular disease, follows distinct 24-hour patterns in occurrence. These 24-hour patterns likely reflect daily changes in arrhythmogenic triggers and the myocardial substrate caused by day/night rhythms in behavior, the environment, and endogenous circadian mechanisms...

Sudden cardiac death (SCD) is the sudden, unexpected death due to abrupt loss of heart function secondary to cardiovascular disease. In certain populations living with cardiovascular disease, SCD follows a distinct 24-hour pattern in occurrence, suggesting day/night rhythms in behavior, the environment, and endogenous circadian rhythms result in da...

Saurabh S Thosar,1–4 Daniel Chess,1 Nicole P Bowles,1 Andrew W McHill,1,2 Matthew P Butler,1,5 Jonathan S Emens,1,6 Steven A Shea1,4 1Oregon Institute of Occupational Health Sciences, Oregon Health & Science University, Portland, OR, USA; 2School of Nursing, Oregon Health & Science University, Portland, OR, USA; 3Knight Cardiovascular Institute, Or...

Asthma often worsens at night. To determine if the endogenous circadian system contributes to the nocturnal worsening of asthma, independent of sleep and other behavioral and environmental day/ night cycles, we studied patients with asthma (without steroid use) over 3 wk in an ambulatory setting (with combined circadian, environmental, and behavior...

Purpose: Sleep efficiency is inversely associated with cardiovascular risk. Brachial artery diameter and flow-mediated dilation (FMD) are noninvasive cardiovascular disease markers. We assessed the associations between sleep efficiency and these vascular markers in midlife adults, including people with sleep apnea. Patients and methods: Thirty (...

Risk for adverse cardiovascular events increases when blood pressure does not decrease at night ("non-dipping", <10% decrease from daytime blood pressure). Shiftwork alters relationships between behaviors and endogenous circadian rhythms (i.e., circadian disruption along with variable sleep timing), and chronic shiftwork increases cardiovascular di...

Purpose: Sedentary behavior and suboptimal sleep increase risks for chronic diseases. We hypothesized that sedentary behavior and sleep affect each other and that an underlying sleep disorder would alter these relationships. To test these hypotheses, we studied the bidirectional relationships between sedentary behavior and sleep (duration and effi...

Background Reduced patient portal use has previously been reported among Black Americans when compared with that of the general population. This statistic is concerning because portals have been shown to improve the control of chronic conditions that are more prevalent and severe in Black Americans. At their very simplest, portals allow patients to...

Introduction Annually, over 60,000 children require critical care admission for acquired brain injury (ABI) in the US, and many face long-term cognitive morbidity. Over 50% of these children also develop sleep/wake disturbances (SWD). Given the importance of sleep to brain development and healing after injury, we hypothesized SWD in children after...

Introduction In the US cannabis is recreationally legal in 15 states and medically legal in 34 states. Preclinical studies suggest beneficial effects of cannabis on the cardiovascular system (e.g., vasorelaxation). Yet, acute cases of hospitalization after cannabis consumption indicate potential adverse cardiac effects. Vascular endothelial functio...

Introduction Cannabis use is on the rise in the United States, with 10% of adults reporting cannabis use in the past 30 days. Users commonly report consuming cannabis to improve sleep despite the lack of research that supports an association between cannabis use and sleep. In this pilot study we sought to examine objective measures of sleep duratio...

Endogenous circadian rhythms prepare the cardiovascular (CV) system for optimal function to match the daily anticipated behavioral and environmental cycles, including variable activities when awake during the day and recuperation when sleeping at night. The overall day-night patterns in most CV variables result from the summation of predictable cir...

BACKGROUND The existence of lower patient portal use among Black Americans is concerning as portals have been shown to improve the control of chronic conditions that are more prevalent and deadlier in Black Americans than the rest of the population. Portal websites at their very simplest connect patients to their electronic health records and often...

Objectives Sedentary behavior is pervasive in the workplace and is harmful to health. Research on the effectiveness of comprehensive workplace interventions to reduce sedentary behavior and improve worker health and safety is crucial as sedentary jobs become more common. Methods We developed a Total Worker Health intervention targeting sedentary b...

Introduction Shift work causes misalignment between internal circadian time and the external light/dark cycle and is associated with metabolic disorders and cancer. Approximately 20% of the working population in industrialised countries work permanent or rotating night shifts, exposing this large population to the risk of circadian misalignment-dri...

Background Firefighters endure large occupational burdens and generally operate under conditions of chronic sleep deficiency and circadian disruption due to long shifts, plus interrupted sleep due to emergency calls during the night. A typical shift for firefighters is 24‐h on/48‐h off, and firefighters are expected to use time‐off to recover from...

Objective: To test the feasibility, acceptability, and potential effectiveness of engineering and behavioral interventions to improve the sleep, health, and well-being of team truck drivers (dyads) who sleep in moving semi-trucks. Methods: Drivers (n = 16) evaluated (A) an innerspring mattress and (B) a novel therapeutic mattress. A subsample (n...

Cardiac death is the second most prevalent cause in Prader-Willi syndrome (PWS). Paediatric patients with PWS often present cardiac autonomic dysfunction during wakefulness, obesity and sleep-disordered breathing. However, the extent of cardiac autonomic modulation during sleep in PWS has not been documented. The objective of this study was to asse...

Cardiac death is the second most prevalent cause in Prader-Willi syndrome (PWS). Paediatric patients with PWS often present cardiac autonomic dysfunction during wakefulness, obesity and sleep-disordered breathing. However, the extent of cardiac autonomic modulation during sleep in PWS has not been documented. The objective of this study was to asse...

ABSTACT In humans, there is an endogenous, near 24-hour (i.e., circadian) variation in mood with the best mood occurring during the circadian day and the worst mood occurring during the circadian night. Only positive affect, and not negative affect, has been shown to contribute to this circadian rhythm. We discovered a sharp circadian peak in negat...

Introduction The prevalence of mood disorders such as depression is higher in individuals with obstructive sleep apnea (OSA). Previous studies have found no significant correlation between the apnea-hypopnea index (AHI) and measures of mood and have only included participants who met diagnostic criteria for OSA. The current analysis sought to deter...

Introduction Cannabis use is on the rise in the US, and while the cannabis plant and related compounds are considered to have low toxicity, the impact on physiology including sleep remains unclear. Further, the bulk of cannabis research has focused on adolescents and young adults despite growing use among the elderly. Thus, this analysis sought to...

Introduction Resting energy expenditure (EE) follows a circadian rhythm in healthy lean participants, with a nadir in the early morning hours. We determined: (1) whether this pattern persists (or how substrate utilization may change), when challenged with exercise, and; (2) whether obesity affects these responses. Methods Fourteen participants (ag...

Introduction Firefighters endure large occupational burdens (e.g., heat, exposure to toxic fumes, witnessed trauma) and generally operate under conditions of chronic sleep deficiency due to long shifts plus disrupted sleep and circadian disruption due to emergency calls during the night. A typical shift for firefighters is 24-hours on/48-hours off,...

Purpose Determine if an uncoupling of bone turnover markers (BTMs) occurs in women exposed to the combination of sleep restriction with circadian disruption (SRCD), as previously reported in men. Methods Four bone biomarkers (N-terminal propeptide of type I procollagen [P1NP] and osteocalcin=bone formation; C-telopeptide [CTX]=bone resorption; scl...

Shift work causes misalignment between our internal clock and daily behavioural cycles and is associated with metabolic disorders and cancer. Here, we describe the relationship between shift work and prevalent asthma in >280,000 UK Biobank participants. Compared to day workers, permanent night shift workers had a higher likelihood of moderate/sever...

Obstructive sleep apnea (OSA) is associated with hypertension, cardiovascular disease, and a change in the 24 h pattern of adverse cardiovascular events and mortality. Adverse cardiovascular events occur more frequently in the middle of the night in people with OSA, earlier than the morning prevalence of these events in the general population. It i...

Sleep is critical to employees' health and well-being, safety, and performance at work. Sleep leadership refers to supervisor behaviors that aim to improve employees' sleep, such as showing concern for the quantity and quality of employees' sleep. Using a sample of 180 employees and their 91 supervisors working as full-time National Guard military...

Study Objectives Recovery rates of systolic blood pressure (BP) and heart rate (HR) after exercise have been used to assess cardiovascular fitness, and slower recovery rates are predictors of coronary heart disease and cardiac mortality. The endogenous circadian system is known to modulate BP and HR at rest and during exercise. Here we examined whe...

We describe the time course of bone formation marker (P1NP) decline in men exposed to ~ 3 weeks of sleep restriction with concurrent circadian disruption. P1NP declined within 10 days and remained lower with ongoing exposure. These data suggest even brief exposure to sleep and circadian disruptions may disrupt bone metabolism. Introduction A serum...

Background: Sleep-wake disturbances are underevaluated among children with acquired brain injury surviving critical care. We aimed to quantify severity, phenotypes, and risk factors for sleep-wake disturbances. Methods: We performed a prospective cohort study of 78 children aged ≥3 years with acquired brain injury within three months of critical...

Objective— Adverse cardiovascular events occur more frequently in the morning than at other times of the day. Vascular endothelial function (VEF)—a robust cardiovascular risk marker—is impaired during this morning period. We recently discovered that this morning impairment in VEF is not caused by either overnight sleep or the inactivity that accomp...

Bone turnover markers (BTMs) display diurnal rhythms. Studies in rats and men suggest sleep restriction and circadian disruption are detrimental to bone metabolism. The effects of sleep and circadian disruption on BTMs in women are unknown. We hypothesized that cumulative sleep restriction and concurrent circadian disruption would decrease P1NP lev...

Introduction Cannabis sativa is commonly used for sleep. Research suggests that acute and heavy cannabis usage have opposing effects on sleep. Recent legalization increased access to cannabis, and provides an opportunity to determine how varying cannabinoid concentrations or duration of use affects sleep and sleepiness. Methods A cross-sectional a...

Introduction Hunger in young, lean individuals is modulated by a circadian rhythm which is lowest near 8AM and peaks around 8PM. Further, later circadian timing of food intake is independently associated with increased body fat. It is unknown, however, whether the circadian rhythm in hunger in non-lean (BMI>25 kg/m²) individuals is delayed or dispr...

Introduction Shift work is a risk factor for elevated plasma levels of low-density lipoprotein cholesterol (LDL-C); yet the underlying mechanisms remain unclear. Proprotein convertase subtilisin/kexin type 9 (PCSK9) is a circulatory protein synthesized mainly by the liver; PCSK9 causes the degradation of the hepatic LDL receptor and thus, increases...

Introduction The endocannabinoid anandamide (AEA) signals ubiquitously throughout the body and has been shown to modulate endocrine systems and sleep/wake cycles. Previous analyses suggest a diurnal variation in plasma levels of AEA. We sought to determine the endogenous circadian profile of AEA and how this distribution may vary by body mass index...

Introduction Adverse cardiovascular (CV) events occur most commonly at ~9 AM in the general population, but ~3 AM in people with obstructive sleep apnea (OSA). Standing up after a night of sleep generates changes in blood pressure (BP) and heart rate (HR) and autonomic activation. We tested whether the CV reactivity to standing is different in OSA...

Measurements of aldosterone for diagnosis of primary aldosteronism are usually made from blood sampled in the morning when aldosterone typically peaks. We tested the relative contributions and interacting influences of the circadian system, ongoing behaviors, and prior sleep to this morning peak in aldosterone. To determine circadian rhythmicity an...

The meta-analysis referenced in the "Obstructive Sleep Apnea" section should instead refer to a meta-analysis for chronic kidney disease. Additionally, there are two mis-numbered reference citations in the “chronic kidney disease” section (ref. 107 should ref. 104 [Wang C et al. 2014] and ref. 105. © 2018, Springer Science+Business Media, LLC, part...

Rationale: Obstructive sleep apnea is a risk factor for mortality, but its diagnostic metric-the apnea-hypopnea index-is a poor risk predictor. The apnea-hypopnea index does not capture the range of physiological variability within and between patients, such as degree of hypoxemia and sleep fragmentation, that reflect differences in pathophysiolog...

Purpose of Review Given the emerging knowledge that circadian rhythmicity exists in every cell and all organ systems, there is increasing interest in the possible benefits of chronotherapy for many diseases. There is a well-documented 24-h pattern of blood pressure with a morning surge that may contribute to the observed morning increase in adverse...

Introduction: Healthy physiological systems exhibit fractal regulation (FR), generating similar fluctuation patterns in physiological outputs across different time scales. FR in motor activity is degraded in dementia, and the degradation correlates to cognitive decline. We tested whether degraded FR predicts Alzheimer's disease dementia. Methods:...

Study objectives: (1) To assess the predictors for obtaining polysomnography (PSG) in children undergoing adenotonsillectomy (AT) for sleep-disordered breathing, and (2) to estimate the adherence to the American Academy of Otolaryngology-Head and Neck Surgery (AAO-HNS) guideline recommendations for pre-AT PSG. Methods: This was a retrospective c...

Cydni N Williams,1 Miranda M Lim,2–5 Steven A Shea5 1Department of Pediatrics, Division of Pediatric Critical Care, 2Department of Neurology, 3Department of Medicine, 4Department of Behavioral Neurosciences, 5Oregon Institute of Occupational Health Sciences, Oregon Health & Science University, Portland, OR, USATraumatic brain injury (TBI), the alte...

All species organize behaviors to optimally match daily changes in the environment, leading to pronounced activity/rest cycles that track the light/dark cycle. Endogenous, approximately 24-hour circadian rhythms in the brain, autonomic nervous system, heart, and vasculature prepare the cardiovascular system for optimal function during these anticip...

Introduction The prevalence of mood and anxiety disorders is higher in individuals with obstructive sleep apnea (OSA). Furthermore, it is known that an endogenous circadian rhythm exists in mood and we have previously shown that both positive and negative affect contribute to this rhythm. We tested whether these rhythms were altered in individuals...

Introduction Healthy physiological systems exhibit fractal regulation, generating similar fluctuation patterns in physiological outputs across different time scales from seconds to hours. Evidence indicates a mechanistic link between fractal regulation and sleep/circadian control, both degraded with aging and in Alzheimer’s disease (AD). Recent stu...

Introduction The influence of circadian timing on glucose regulation has been well-studied in normal-weight humans, but is poorly understood in obese individuals. We therefore sought to test whether obesity influenced the relationships between circadian timing and pre/post-prandial glucose and insulin responses. Methods After 1–3 weeks of maintain...

Introduction Maximum risk for adverse cardiovascular events (e.g., myocardial infarction, stroke) occurs in the morning hours (~6AM-12PM). These time-of-day variations may be due to effects of daily rhythms in behaviors or the circadian system on cardiovascular function. Cognitive stress is one behavioral factor that may contribute to the morning p...

Adequate sleep timed appropriately during the circadian night is important for numerous biological processes and systems. New evidence suggests that both sleep timing and duration may be important for optimal bone health as well. This review examines the diurnal variation of bone turnover markers (BTMs) and the importance of circadian clock genes i...

Nicole P Bowles, Maya X Herzig, Steven A Shea Oregon Institute of Occupational Health Sciences, Oregon Health & Science University, Portland, OR, USAThe recent legalization of cannabis for medical and recreational use in many states in the United States and internationally4,5 has resulted in a decrease in stigma and of perceived risk of cannabis us...

Introduction: The osteocyte exerts important effects on bone remodeling, but its rhythmicity and effect on the rhythms of other bone cells are not fully characterized. The purpose of this study was to determine if serum sclerostin displays rhythmicity over a 24-h interval, similar to that of other bone biomarkers. Methods: Serum sclerostin, FGF-...

Context Sleep abnormalities are associated with low bone mineral density (BMD). Underlying mechanisms are unknown. Objective Investigate the impact of sleep restriction with circadian disruption on bone biomarkers. Hypothesis Sleep/circadian disruption negatively alters bone turnover. Design Intervention Study Participants & Methods Four bone b...

Introduction Double product (DP), the product of heart rate and systolic pressure, is a non-invasive index of myocardial oxygen consumption commonly used for cardiovascular (CV) risk stratification. In the general population, DP peaks in the afternoon, but whether the endogenous circadian system contributes to the day/night pattern is unknown. We t...