Effects of sleep disturbance on dyspnoea and impaired lung function following hospital admission due to COVID-19 in the UK: a prospective multicentre cohort study

BACKGROUND

Sleep disturbance is common following hospital admission both for COVID-19 and other causes. The clinical associations of this for recovery after hospital admission are poorly understood despite sleep disturbance contributing to morbidity in other scenarios. We aimed to investigate the prevalence and nature of sleep disturbance after discharge following hospital admission for COVID-19 and to assess whether this was associated with dyspnoea.

METHODS

CircCOVID was a prospective multicentre cohort substudy designed to investigate the effects of circadian disruption and sleep disturbance on recovery after COVID-19 in a cohort of participants aged 18 years or older, admitted to hospital for COVID-19 in the UK, and discharged between March, 2020, and October, 2021. Participants were recruited from the Post-hospitalisation COVID-19 study (PHOSP-COVID). Follow-up data were collected at two timepoints: an early time point 2-7 months after hospital discharge and a later time point 10-14 months after hospital discharge. Sleep quality was assessed subjectively using the Pittsburgh Sleep Quality Index questionnaire and a numerical rating scale. Sleep quality was also assessed with an accelerometer worn on the wrist (actigraphy) for 14 days. Participants were also clinically phenotyped, including assessment of symptoms (ie, anxiety [Generalised Anxiety Disorder 7-item scale questionnaire], muscle function [SARC-F questionnaire], dyspnoea [Dyspnoea-12 questionnaire] and measurement of lung function), at the early timepoint after discharge. Actigraphy results were also compared to a matched UK Biobank cohort (non-hospitalised individuals and recently hospitalised individuals). Multivariable linear regression was used to define associations of sleep disturbance with the primary outcome of breathlessness and the other clinical symptoms. PHOSP-COVID is registered on the ISRCTN Registry (ISRCTN10980107).

FINDINGS

2320 of 2468 participants in the PHOSP-COVID study attended an early timepoint research visit a median of 5 months (IQR 4-6) following discharge from 83 hospitals in the UK. Data for sleep quality were assessed by subjective measures (the Pittsburgh Sleep Quality Index questionnaire and the numerical rating scale) for 638 participants at the early time point. Sleep quality was also assessed using device-based measures (actigraphy) a median of 7 months (IQR 5-8 months) after discharge from hospital for 729 participants. After discharge from hospital, the majority (396 [62%] of 638) of participants who had been admitted to hospital for COVID-19 reported poor sleep quality in response to the Pittsburgh Sleep Quality Index questionnaire. A comparable proportion (338 [53%] of 638) of participants felt their sleep quality had deteriorated following discharge after COVID-19 admission, as assessed by the numerical rating scale. Device-based measurements were compared to an age-matched, sex-matched, BMI-matched, and time from discharge-matched UK Biobank cohort who had recently been admitted to hospital. Compared to the recently hospitalised matched UK Biobank cohort, participants in our study slept on average 65 min (95% CI 59 to 71) longer, had a lower sleep regularity index (-19%; 95% CI -20 to -16), and a lower sleep efficiency (3·83 percentage points; 95% CI 3·40 to 4·26). Similar results were obtained when comparisons were made with the non-hospitalised UK Biobank cohort. Overall sleep quality (unadjusted effect estimate 3·94; 95% CI 2·78 to 5·10), deterioration in sleep quality following hospital admission (3·00; 1·82 to 4·28), and sleep regularity (4·38; 2·10 to 6·65) were associated with higher dyspnoea scores. Poor sleep quality, deterioration in sleep quality, and sleep regularity were also associated with impaired lung function, as assessed by forced vital capacity. Depending on the sleep metric, anxiety mediated 18-39% of the effect of sleep disturbance on dyspnoea, while muscle weakness mediated 27-41% of this effect.

INTERPRETATION

Sleep disturbance following hospital admission for COVID-19 is associated with dyspnoea, anxiety, and muscle weakness. Due to the association with multiple symptoms, targeting sleep disturbance might be beneficial in treating the post-COVID-19 condition.

FUNDING

UK Research and Innovation, National Institute for Health Research, and Engineering and Physical Sciences Research Council.

Circadian regulation of pulmonary disease: the importance of timing

Circadian regulation causes the activity of biological processes to vary over a 24-h cycle. The pathological effects of this variation are predominantly studied using two different approaches: pre-clinical models or observational clinical studies. Both these approaches have provided useful insights into how underlying circadian mechanisms operate and specifically which are regulated by the molecular oscillator, a key time-keeping mechanism in the body. This review compares and contrasts findings from these two approaches in the context of four common respiratory diseases (asthma, chronic obstructive pulmonary disease, pulmonary fibrosis, and respiratory infection). Potential methods used to identify and measure human circadian oscillations are also discussed as these will be useful outcome measures in future interventional human trials that target circadian mechanisms.

ClinCirc identifies alterations of the circadian peripheral oscillator in critical care patients

BackgroundAssessing circadian rhythmicity from infrequently sampled data is challenging; however, these types of data are often encountered when measuring circadian transcripts in hospitalized patients.MethodsWe present ClinCirc. This method combines 2 existing mathematical methods (Lomb-Scargle periodogram and cosinor) sequentially and is designed to measure circadian oscillations from infrequently sampled clinical data. The accuracy of this method was compared against 9 other methods using simulated and frequently sampled biological data. ClinCirc was then evaluated in 13 intensive care unit (ICU) patients as well as in a separate cohort of 29 kidney-transplant recipients. Finally, the consequences of circadian alterations were investigated in a retrospective cohort of 726 kidney-transplant recipients.ResultsClinCirc had comparable performance to existing methods for analyzing simulated data or clock transcript expression of healthy volunteers. It had improved accuracy compared with the cosinor method in evaluating circadian parameters in PER2:luc cell lines. In ICU patients, it was the only method investigated to suggest that loss of circadian oscillations in the peripheral oscillator was associated with inflammation, a feature widely reported in animal models. Additionally, ClinCirc was able to detect other circadian alterations, including a phase shift following kidney transplantation that was associated with the administration of glucocorticoids. This phase shift could explain why a significant complication of kidney transplantation (delayed graft dysfunction) oscillates according to the time of day kidney transplantation is performed.ConclusionClinCirc analysis of the peripheral oscillator reveals important clinical associations in hospitalized patients.FundingUK Research and Innovation (UKRI), National Institute of Health Research (NIHR), Engineering and Physical Sciences Research Council (EPSRC), National Institute on Academic Anaesthesia (NIAA), Asthma+Lung UK, Kidneys for Life.

Adipocyte NR1D1 dictates adipose tissue expansion during obesity

The circadian clock component NR1D1 (REVERBα) is considered a dominant regulator of lipid metabolism, with global Nr1d1 deletion driving dysregulation of white adipose tissue (WAT) lipogenesis and obesity. However, a similar phenotype is not observed under adipocyte-selective deletion (Nr1d1Flox2-6:AdipoqCre), and transcriptional profiling demonstrates that, under basal conditions, direct targets of NR1D1 regulation are limited, and include the circadian clock and collagen dynamics. Under high-fat diet (HFD) feeding, Nr1d1Flox2-6:AdipoqCre mice do manifest profound obesity, yet without the accompanying WAT inflammation and fibrosis exhibited by controls. Integration of the WAT NR1D1 cistrome with differential gene expression reveals broad control of metabolic processes by NR1D1 which is unmasked in the obese state. Adipocyte NR1D1 does not drive an anticipatory daily rhythm in WAT lipogenesis, but rather modulates WAT activity in response to alterations in metabolic state. Importantly, NR1D1 action in adipocytes is critical to the development of obesity-related WAT pathology and insulin resistance.

Timekeeping in the hindbrain: a multi-oscillatory circadian centre in the mouse dorsal vagal complex

Metabolic and cardiovascular processes controlled by the hindbrain exhibit 24 h rhythms, but the extent to which the hindbrain possesses endogenous circadian timekeeping is unresolved. Here we provide compelling evidence that genetic, neuronal, and vascular activities of the brainstem’s dorsal vagal complex are subject to intrinsic circadian control with a crucial role for the connection between its components in regulating their rhythmic properties. Robust 24 h variation in clock gene expression in vivo and neuronal firing ex vivo were observed in the area postrema (AP) and nucleus of the solitary tract (NTS), together with enhanced nocturnal responsiveness to metabolic cues. Unexpectedly, we also find functional and molecular evidence for increased penetration of blood borne molecules into the NTS at night. Our findings reveal that the hindbrain houses a local network complex of neuronal and non-neuronal autonomous circadian oscillators, with clear implications for understanding local temporal control of physiology in the brainstem.

Lukasz Chrobok, Rebecca Northeast et al. show circadian variation in clock gene expression and neuronal firing within the area postrema and the nucleus of the solitary tract in mice. These regions also exhibit variation in metabolic processes and blood-brain barrier permeability across the 24 hour cycle suggesting the presence of circadian oscillators within the dorsal vagal complex.

The clock gene Bmal1 inhibits macrophage motility, phagocytosis, and impairs defense against pneumonia

The circadian clock regulates many aspects of immunity. Bacterial infections are affected by time of day, but the mechanisms involved remain undefined. Here we show that loss of the core clock protein BMAL1 in macrophages confers protection against pneumococcal pneumonia. Infected mice show both reduced weight loss and lower bacterial burden in circulating blood. In vivo studies of macrophage phagocytosis reveal increased bacterial ingestion following Bmal1 deletion, which was also seen in vitro. BMAL1-/- macrophages exhibited marked differences in actin cytoskeletal organization, a phosphoproteome enriched for cytoskeletal changes, with reduced phosphocofilin and increased active RhoA. Further analysis of the BMAL1-/- macrophages identified altered cell morphology and increased motility. Mechanistically, BMAL1 regulated a network of cell movement genes, 148 of which were within 100 kb of high-confidence BMAL1 binding sites. Links to RhoA function were identified, with 29 genes impacting RhoA expression or activation. RhoA inhibition restored the phagocytic phenotype to that seen in control macrophages. In summary, we identify a surprising gain of antibacterial function due to loss of BMAL1 in macrophages, associated with a RhoA-dependent cytoskeletal change, an increase in cell motility, and gain of phagocytic function.

The circadian clock protein REVERBα inhibits pulmonary fibrosis development

Pulmonary inflammatory responses lie under circadian control; however, the importance of circadian mechanisms in the underlying fibrotic phenotype is not understood. Here, we identify a striking change to these mechanisms resulting in a gain of amplitude and lack of synchrony within pulmonary fibrotic tissue. These changes result from an infiltration of mesenchymal cells, an important cell type in the pathogenesis of pulmonary fibrosis. Mutation of the core clock protein REVERBα in these cells exacerbated the development of bleomycin-induced fibrosis, whereas mutation of REVERBα in club or myeloid cells had no effect on the bleomycin phenotype. Knockdown of REVERBα revealed regulation of the little-understood transcription factor TBPL1. Both REVERBα and TBPL1 altered integrinβ1 focal-adhesion formation, resulting in increased myofibroblast activation. The translational importance of our findings was established through analysis of 2 human cohorts. In the UK Biobank, circadian strain markers (sleep length, chronotype, and shift work) are associated with pulmonary fibrosis, making them risk factors. In a separate cohort, REVERBα expression was increased in human idiopathic pulmonary fibrosis (IPF) lung tissue. Pharmacological targeting of REVERBα inhibited myofibroblast activation in IPF fibroblasts and collagen secretion in organotypic cultures from IPF patients, thus suggesting that targeting of REVERBα could be a viable therapeutic approach.

Incidence of primary graft dysfunction after lung transplantation is altered by timing of allograft implantation

The importance of circadian factors in managing patients is poorly understood. We present two retrospective cohort studies showing that lungs reperfused between 4 and 8 AM have a higher incidence (OR 1.12; 95% CI 1.03 to 1.21; p=0.01) of primary graft dysfunction (PGD) in the first 72 hours after transplantation. Cooling of the donor lung, occurring during organ preservation, shifts the donor circadian clock causing desynchrony with the recipient. The clock protein REV-ERBα directly regulates PGD biomarkers explaining this circadian regulation while also allowing them to be manipulated with synthetic REV-ERB ligands.

Adiponectin induces A20 expression in adipose tissue to confer metabolic benefit

Obesity is a major risk factor for metabolic disease, with white adipose tissue (WAT) inflammation emerging as a key underlying pathology. We detail that mice lacking Reverbα exhibit enhanced fat storage without the predicted increased WAT inflammation or loss of insulin sensitivity. In contrast to most animal models of obesity and obese human patients, Reverbα(-/-) mice exhibit elevated serum adiponectin levels and increased adiponectin secretion from WAT explants in vitro, highlighting a potential anti-inflammatory role of this adipokine in hypertrophic WAT. Indeed, adiponectin was found to suppress primary macrophage responses to lipopolysaccharide and proinflammatory fatty acids, and this suppression depended on glycogen synthase kinase 3β activation and induction of A20. Attenuated inflammatory responses in Reverbα(-/-) WAT depots were associated with tonic elevation of A20 protein and ex vivo shown to depend on A20. We also demonstrate that adipose A20 expression in obese human subjects exhibits a negative correlation with measures of insulin sensitivity. Furthermore, bariatric surgery-induced weight loss was accompanied by enhanced WAT A20 expression, which is positively correlated with increased serum adiponectin and improved metabolic and inflammatory markers, including C-reactive protein. The findings identify A20 as a mediator of adiponectin anti-inflammatory action in WAT and a potential target for mitigating obesity-related pathology.

Creative thought in neurosurgical research: the value of citation analysis

Creative research thought, embodying original ideas that are adaptable and lasting, changes the scholarship and course of neurosurgery, and will be recognized by high citation frequency. Thirty-nine of 50 of the first American neurosurgeons were the first authors of 411 research papers, which were studied by analysis of citations between 1965 and 1979. Of all papers written by these authors between 1896 and 1976, 11% concerned research; this category received 22% of the aggregate of citations. The five research areas that received the largest number of citations were brain tumors (745), central nervous system physiology (279), experimental hydrocephalus (232), increased intracranial pressure (222), and head injury (107). Solutions to these problems were resolved with varying degrees of success. Interest in brain tumor research was reflected by the use of special staining techniques in 30% of these papers. Seventy percent of neurosurgical research papers appeared in clinical journals. The Archives of Neurology and Psychiatry had the largest number of papers and of total citations for journals. The paper cited most often was Dandy's, "Internal Hydrocephalus: An Experimental, Clinical, and Pathological Study." Cushing and Penfield each wrote 3 of the 10 most cited research papers. The most productive research authors were also most often cited. They included Bailey (441), Cushing (431), Penfield (423), Dandy (246), and Davis (158). Among the 50 authors, the percentage of published research papers did not separate the neurosurgeon with laboratory experience from his clinically oriented counterpart with regard to productivity and creativity. The data suggest that neurosurgeons are generally not basic scientists but clinical investigators.

Prognostic factors in severe head injury

Head injury is a significant economic, social and medical problem in the United States. For this reason, prognostic factors in head injury are of major importance to all surgeons who treat severely injured patients. Outcome of severe head injury is frequently determined at the time of impact, and surgical and medical treatment is often ineffective. Prediction of outcome of severe head injury should be based upon early neurologic signs, including degree of coma as measured by the Glasgow Coma Scale, brain stem reflexes, central nervous system lesion type, presence of increased intracranial pressure and multimodality evoked responses. The Glasgow Coma Scale is a standardized measurement of coma which numerically rates the response of eye opening, verbal response and motor response of the patient with head injury. The Glasgow coma score, the sum of the three response ratings, correlates with mortality of head injury, although the correlation between the coma score and morbidity has not been conclusively established. Because injury to the brain stem is generally irreversible, absence of oculocephalic reflexes, oculovestibular reflexes and pupillary response and the presence of decerebrate rigidity indicate an unfavorable outcome. Patients with focal brain injuries, especially subdural hematomas, generally have a higher mortality than patients who have diffuse brain injuries, regardless of the Glasgow coma score. Elevated intracranial pressure indicates an unfavorable outcome, especially if not reducible. Increased age and hypotension also subject patients with head injury to greater risk. Multiple injuries do not affect mortality of head injury. Multimodality evoked responses are a noninvasive prognostic technique which predicts outcome with a high degree of certainty. For optimal accuracy, prognosis should be based upon a combination of factors, including age, Glasgow coma score, pupillary response, eye movements, presence of surgical lesion, motor posturing and multimodality evoked responses. Decisions regarding surgical and medical treatment of patients with head injury should be based upon these prognostic factors.