Publications

Despite the growing research base examining the benefits and physiological mechanisms of slow-paced breathing (SPB), mindfulness (M), and their combination (as yogic breathing, SPB + M), no studies have directly compared these in a "dismantling" framework. To address this gap, we conducted a fully remote three-armed feasibility study with wearable devices and video-based laboratory visits. Eighteen healthy participants (age 18-30 years, 12 female) were randomized to one of three 8-week interventions: slow-paced breathing (SPB, N = 5), mindfulness (M, N = 6), or yogic breathing (SPB + M, N = 7). The participants began a 24-h heart rate recording with a chest-worn device prior to the first virtual laboratory visit, consisting of a 60-min intervention-specific training with guided practice and experimental stress induction using a Stroop test. The participants were then instructed to repeat their assigned intervention practice daily with a guided audio, while concurrently recording their heart rate data and completing a detailed practice log. The feasibility was determined using the rates of overall study completion (100%), daily practice adherence (73%), and the rate of fully analyzable data from virtual laboratory visits (92%). These results demonstrate feasibility for conducting larger trial studies with a similar fully remote framework, enhancing the ecological validity and sample size that could be possible with such research designs.

STUDY OBJECTIVE: To evaluate how nocturnal timing of sleep restriction affects vigilant attention and mood in healthy controls with normal sleep-wake patterns.

METHODS: A convenience sample from two controlled sleep restriction protocols were used to investigate the difference between 4 hours of sleep early in the night, versus 4 hours late in the night. Volunteers stayed in a hospital setting and were randomized to one of the three conditions: a control (8 hours of sleep each night), an early short sleep (ESS, 2300-0300 hours), and a late short sleep (LSS, 0300-0700 hours). Participants were evaluated with psychomotor vigilance task (PVT) and mood ratings via visual analog scales.

RESULTS: Short sleep conditions led to greater performance decrements than control on PVT. LSS performance impairments were greater than control (lapses, p = 0.011; median RT, p = 0.029; fastest 10%, p = 0.038; reciprocal RT, p = 0.014; and reciprocal 10%, p = 0.005), but had higher positive mood ratings (p = 0.005). LSS also had higher positive mood ratings compared with ESS (p < 0.001).

CONCLUSIONS: The data underscore the negative mood impact of waking at an adverse circadian phase, for healthy controls. In addition, the paradoxical relationship between mood and performance seen in LSS raises concerns that staying up late and waking at the usual rise time may be rewarding in terms of mood, but nonetheless have performance consequences that may not be fully recognized.

CHAPTER HIGHLIGHTS

• That sleep is altered during sickness has been known for millennia. Yet, systematic and controlled studies aimed at elucidating the extent to which sleep is altered in response to immune challenge have only been conducted during the last 30 years.

• Substances historically viewed as components of the innate immune system are now known to be involved in the regulation or modulation of physiological sleep-wake behavior, in the absence of immune challenge. Changes in sleep during immune challenge are actively driven and result from amplification of these physiological mechanisms.
   
• Although the precise changes in sleep-wake behavior depend on the pathogen, route of infection, timing of infection, host species, and other factors, altered sleep during immune challenge is generally characterized by periods of increased non-rapid eye movements (NREM) sleep, increased delta power during NREM sleep, and suppressed REM sleep. Infection-induced alterations in sleep are often accompanied by fever or hypothermia.
   
• Altered sleep has been studied in humans during pathologies and/or infections with pathogens including HIV/AIDS, rhinovirus (common cold), streptococci, trypanosomes, prions, and sepsis. Laboratory animal models include sepsis, influenza and other viruses (gammaherpes virus, vesicular stomatitis virus, rabies, feline immunodeficiency virus), several bacterial species, trypanosomes, and several prion diseases.
   
• Mechanisms that link sleep to innate immunity involve a biochemical brain network composed of cytokines, chemokines, growth factors, transcription factors, neurotransmitters, enzymes and their receptors.  Each of these substances and receptors is present in neurons, although interactions with glia are critical for host defense responses to immune challenge. Redundancy, feed-forward, and feed-back loops are characteristic of this biochemical network. These attributes provide stability and flexibility to the organismal response to immune challenge.

Sleep disturbances, including disrupted sleep and short sleep duration, are highly prevalent and are prospectively associated with an increased risk for various widespread diseases, including cardiometabolic, neurodegenerative, chronic pain, and autoimmune diseases. Systemic inflammation, which has been observed in populations experiencing sleep disturbances, may mechanistically link disturbed sleep with increased disease risks. To determine whether sleep disturbances are causally responsible for the inflammatory changes reported in population-based studies, we developed a 19-day in-hospital experimental model of prolonged sleep disturbance inducing disrupted and shortened sleep. The model included delayed sleep onset, frequent nighttime awakenings, and advanced sleep offset, interspersed with intermittent nights of undisturbed sleep. This pattern aimed at providing an ecologically highly valid experimental model of the typical sleep disturbances often reported in the general and patient populations. Unexpectedly, the experimental sleep disturbance model reduced several of the assessed proinflammatory markers, namely interleukin(IL)-6 production by monocytes and plasma levels of IL-6 and C-reactive protein (CRP), presumably due to intermittent increases in the counterinflammatory hormone cortisol. Striking sex differences were observed with females presenting a reduction in proinflammatory markers and males showing a predominantly proinflammatory response and reductions of cortisol levels. Our findings indicate that sleep disturbances causally dysregulate inflammatory pathways, with opposing effects in females and males. These results have the potential to advance our mechanistic understanding of the pronounced sexual dimorphism in the many diseases for which sleep disturbances are a risk factor.

Sleep is one of the pillars of health. Experimental models of acute sleep loss, of chronic partial sleep deprivation, and of sleep fragmentation in healthy sleepers are helpful models of sleep deficiency produced by insufficient sleep duration, sleep timing, and sleep disorders. Sleep deficiency is associated with changes in markers associated with risk for disease. These include metabolic, inflammatory, and autonomic markers of risk. In addition, sleep disruption and sleep deficits lead to mood instability, lack of positive outlook, and impaired neurobehavioral functioning. On a population level, insufficient sleep is associated with increased risk for hypertension and diabetes. Sleep disturbance is very common, and about half the population will report that they have experienced insomnia at some time in their lives. Approximately 10% of the population describe daytime impairment due to sleep disturbance at night, consistent with a diagnosis of insomnia disorder. The hypothalamic neuropeptides, orexin-A and orexin-B, act through G-protein-coupled receptors (orexin-1 and orexin-2 receptors). Dual and selective orexin-2 receptor antagonists have shown efficacy in inducing sleep in men and women with insomnia disorder by accelerating sleep onset and improving sleep efficiency and total sleep time. Further study comparing these medications, in short- and longer-term use models, is recommended. Greater understanding of comparative effects on mood, neurobehavioral, and physiological systems will help determine the extent of clinical utility of dual versus selective orexin receptor antagonists.

Epidemiological studies have reported strong association between sleep loss and hypertension with unknown mechanisms. This study investigated macrovascular and microcirculation changes and inflammatory markers during repetitive sleep restriction. Sex differences were also explored. Forty-five participants completed a 22-day in-hospital protocol. Participants were assigned to, (1) eight-hour sleep per night (control), or (2) sleep restriction (SR) condition: participants slept from 0300 to 0700 h for three nights followed by a recovery night of 8-h sleep, repeated four times. Macrocirculation assessed by flow mediated dilation (FMD) and microcirculation reactivity tests were performed at baseline, last day of each experimental block and during recovery at the end. Cell adhesion molecules and inflammatory marker levels were measured in blood samples. No duration of deprivation (SR block) by condition interaction effects were found for FMD, microcirculation, norepinephrine, cell adhesion molecules, IL-6 or IL-8. However, when men and women were analyzed separately, there was a statistical trend (p = 0.08) for increased IL-6 across SR blocks in women, but not in men. Interestingly, men showed a significant progressive (dose dependent) increase in skin vasodilatation (p = 0.02). A novel and unexpected finding was that during the recovery period, men that had been exposed to repeated SR blocks had elevated IL-8 and decreased norepinephrine. Macrocirculation, microcirculation, cell adhesion molecules, and markers of inflammation appeared to be resistant to this model of short-term repetitive exposures to the blocks of shortened sleep in healthy sleepers. However, men and women responded differently, with women showing mild inflammatory response and men showing more vascular system sensitivity to the repetitive SR.

Pain can be both a cause and a consequence of sleep deficiency. This bidirectional relationship between sleep and pain has important implications for clinical management of patients, but also for chronic pain prevention and public health more broadly. The review that follows will provide an overview of the neurobiological evidence of mechanisms thought to be involved in the modulation of pain by sleep deficiency, including the opioid, monoaminergic, orexinergic, immune, melatonin, and endocannabinoid systems; the hypothalamus-pituitary-adrenal axis; and adenosine and nitric oxide signaling. In addition, it will provide a broad overview of pharmacological and non-pharmacological approaches for the management of chronic pain comorbid with sleep disturbances and for the management of postoperative pain, as well as discuss the effects of sleep-disturbing medications on pain amplification.

Recent discoveries demonstrate a critical role for circadian rhythms and sleep in immune system homeostasis. Both innate and adaptive immune responses - ranging from leukocyte mobilization, trafficking, and chemotaxis to cytokine release and T cell differentiation -are mediated in a time of day-dependent manner. The National Institutes of Health (NIH) recently sponsored an interdisciplinary workshop, "Sleep Insufficiency, Circadian Misalignment, and the Immune Response," to highlight new research linking sleep and circadian biology to immune function and to identify areas of high translational potential. This Review summarizes topics discussed and highlights immediate opportunities for delineating clinically relevant connections among biological rhythms, sleep, and immune regulation.

Sleep and immunity are bidirectionally linked. Immune system activation alters sleep, and sleep in turn affects the innate and adaptive arm of our body's defense system. Stimulation of the immune system by microbial challenges triggers an inflammatory response, which, depending on its magnitude and time course, can induce an increase in sleep duration and intensity, but also a disruption of sleep. Enhancement of sleep during an infection is assumed to feedback to the immune system to promote host defense. Indeed, sleep affects various immune parameters, is associated with a reduced infection risk, and can improve infection outcome and vaccination responses. The induction of a hormonal constellation that supports immune functions is one likely mechanism underlying the immune-supporting effects of sleep. In the absence of an infectious challenge, sleep appears to promote inflammatory homeostasis through effects on several inflammatory mediators, such as cytokines. This notion is supported by findings that prolonged sleep deficiency (e.g., short sleep duration, sleep disturbance) can lead to chronic, systemic low-grade inflammation and is associated with various diseases that have an inflammatory component, like diabetes, atherosclerosis, and neurodegeneration. Here, we review available data on this regulatory sleep-immune crosstalk, point out methodological challenges, and suggest questions open for future research.

Despite known associations of insomnia disorder with alterations in cytokine and glucocorticoid (GC) production, neither the sensitivity of immune cells to a GC signal nor the reactivity of the hypothalamus-pituitary-adrenal (HPA) axis and inflammatory system to stress, or adaptation of these systems to repeated stress have been assessed in patients with insomnia. To investigate potential dysregulation in stress reactivity and adaptation to repeated exposure, a physiological stressor (the cold pressor test; CPT) was repeatedly administered to N = 20 participants with insomnia disorder (based on DSM-V, 18 females, age 30 ± 2.5 years) and N = 20 sex-matched healthy controls following an at-home actigraphy and in-laboratory PSG. HPA and inflammatory markers (serum cortisol, plasma interleukin [IL]-6) were measured at baseline/resting levels and following each of the three CPTs. In addition, sensitivity of monocytes to the synthetic GC dexamethasone was assessed in-vitro at baseline levels in order to examine the cortisol-IL-6 interplay at the cell level. Compared to healthy controls, individuals with insomnia disorder exhibited shorter sleep duration as assessed by actigraphy and PSG (p ≤ 0.05). HPA, but not inflammatory reactivity to the repeated CPT challenge was greater in insomnia disorder (p ≤ 0.05 for group effect), due to greater cortisol responses to the initial CPT (p ≤ 0.05). There were no between-group differences in the ability of the HPA to adapt to stress repetition nor in basal/resting levels of cortisol, IL-6, and GC sensitivity. These findings suggest that insomnia disorder potentiates HPA axis reactivity to initial/novel stressors, which may constitute a pathway underlying adverse health consequences in the long term.