Sleep Fragmentation and Cognitive Trajectories After Critical Illness

Association of sleep fragmentation with general and abdominal obesity: a population-based longitudinal study

OBJECTIVE

To evaluate the causal relationship between sleep fragmentation (SF) parameters with general and abdominal obesity in free-living conditions.

METHODS

SF parameters were assessed by ActiGraph accelerometers for 7 consecutive days. Obesity was measured at baseline and 1-year follow-up with InBody S10 body composition analyzer.

RESULTS

At baseline, the mean age of the study population was 18.7 years old (SD = 0.9) and 139 (35.7%) were male. Each 1-unit increase of baseline sleep fragmentation index (SFI) was associated with 0.08 kg/m2-increase of body mass index (BMI) (95% CI: 0.03, 0.14), 0.20%-increase of percentage of body fat (PBF) (95% CI: 0.07, 0.32), 0.15 kg-increase of fat mass (FM) (95% CI: 0.03, 0.27), 0.15 cm-increase of waist circumference (WC) (95% CI: 0.03, 0.26) and 0.91 cm2-increase of visceral fat area (VFA) (95% CI: 0.36, 1.46) at the 1-year follow-up. In addition, each 1-unit increase of baseline SFI was associated with 15% increased risk of general obesity (OR = 1.15, 95% CI = 1.04-1.28; p = 0.006) and 7% increased risk of abdominal obesity (OR = 1.07, 95% CI = 1.01-1.13; p = 0.021) in the following year.

CONCLUSIONS

Fragmented sleep is independently associated with an increased risk of both general and abdominal obesity. The result highlights SF as a modifiable risk factor for the prevention and treatment of obesity.

Impact of Preoperative Sleep Disturbances on Postoperative Delirium in Patients with Intracranial Tumors: A Prospective, Observational, Cohort Study

Background

Postoperative delirium (POD) is prevalent in craniotomy patients and is associated with high mortality. Sleep disturbances are receiving increasing attention from clinicians as associated risk factors for postoperative complications. This study aimed to determine the impact of preoperative sleep disturbances on POD in craniotomy patients.

Methods

We recruited 130 patients undergoing elective craniotomy for intracranial tumors between May 1st and December 30th, 2022. Preoperative subjective sleep disturbances were assessed using the Pittsburgh Sleep Quality Index on the day of admission. We also measured objective perioperative sleep patterns using a dedicated sleep monitoring device 3 days before and 3 days after the surgery. POD was assessed twice daily using the Confusion Assessment Model for the Intensive Care Unit within the first week after craniotomy.

Results

Preoperative sleep disturbances were diagnosed in 49% of the study patients, and POD was diagnosed in 22% of all the study patients. Sleep disturbances were an independent risk factor for POD (OR: 2.709, 95% CI: 1.020-7.192, P = 0.045). Other risk factors for POD were age (OR: 3.038, 95% CI: 1.195-7.719, P = 0.020) and the duration of urinary catheterization (OR: 1.246, 95% CI: 1.025-1.513, P = 0.027). Perioperative sleep patterns (including sleep latency, deep sleep duration, frequency of awakenings, apnea-hypopnea index, and sleep efficiency) were significantly associated with POD.

Conclusion

This study demonstrated that preoperative sleep disturbances predispose patients undergoing craniotomy to POD, also inferred a correlation between perioperative sleep patterns and POD. The targeted screening and intervention specifically for sleep disturbances during the perioperative period are immensely required.

Nurses' experiences of managing cognitive problems in intensive care unit patients: A qualitative study

OBJECTIVES

Nurses hold a key position in identifying symptoms and initiating preventive strategies for cognitive impairment in delirious and non-delirious intensive care unit patients. However, it remains unclear whether nurses consider cognitive impairment as a distinct concern from delirium. By understanding nurses' perspectives, we may identify barriers and facilitators in caring for patients with cognitive challenges in the intensive care unit. The objective of this study was to explore nurses' experiences of cognitive problems in patients admitted to an intensive care unit.

RESEARCH METHODOLOGY

A phenomenological-hermeneutic study of interviews with ten nurses from intensive care units. Data were collected in March-April 2022 and analysed using a Ricœur-inspired method of interpretation.

FINDINGS

Three themes related to nurses' experiences of cognitive problems emerged through analysis; 1) Cognitive problems and delirium are seen as two sides of the same coin, 2) Searching for the person behind the patient, and 3) Maintaining a sense of normality in a confusing environment.

CONCLUSIONS

The interconnected concept of cognitive impairment and delirium syndrome meant that nurses assessed and managed cognitive problems in intensive care unit patients by focusing on preventing delirium. Apart from delirium screening, nurses relied on relatives' knowledge to assess patients' cognition. Most significantly, our study revealed a previously unexplored approach by nurses to manage patients' cognition, which involved "shielding" patients from the noisy and disruptive intensive care unit environment.

IMPLICATIONS FOR CLINICAL PRACTICE

Effective communication methods, coupled with family involvement may aid nurses in identifying patients' cognitive problems. In the acute phase of critical illness, distinguishing between delirium and cognitive problems may not be clinically relevant, as delirium protocols may protect patients' cognition. Further investigating the concept of shielding may reveal previously unexplored nursing approaches to manage cognitive problems.

Sleep and critical illness: a review

Critical illness and stays in the Intensive Care Unit (ICU) have significant impact on sleep. Poor sleep is common in this setting, can persist beyond acute critical illness, and is associated with increased morbidity and mortality. In the past 5 years, intensive care clinical practice guidelines have directed more focus on sleep and circadian disruption, spurring new initiatives to study and improve sleep complications in the critically ill. The global SARS-COV-2 (COVID-19) pandemic and dramatic spikes in patients requiring ICU level care also brought augmented levels of sleep disruption, the understanding of which continues to evolve. This review aims to summarize existing literature on sleep and critical illness and briefly discuss future directions in the field.

Sleep during and following critical illness: A narrative review

Sleep is a complex process influenced by biological and environmental factors. Disturbances of sleep quantity and quality occur frequently in the critically ill and remain prevalent in survivors for at least 12 mo. Sleep disturbances are associated with adverse outcomes across multiple organ systems but are most strongly linked to delirium and cognitive impairment. This review will outline the predisposing and precipitating factors for sleep disturbance, categorised into patient, environmental and treatment-related factors. The objective and subjective methodologies used to quantify sleep during critical illness will be reviewed. While polysomnography remains the gold-standard, its use in the critical care setting still presents many barriers. Other methodologies are needed to better understand the pathophysiology, epidemiology and treatment of sleep disturbance in this population. Subjective outcome measures, including the Richards-Campbell Sleep Questionnaire, are still required for trials involving a greater number of patients and provide valuable insight into patients’ experiences of disturbed sleep. Finally, sleep optimisation strategies are reviewed, including intervention bundles, ambient noise and light reduction, quiet time, and the use of ear plugs and eye masks. While drugs to improve sleep are frequently prescribed to patients in the ICU, evidence supporting their effectiveness is lacking.

Causes, Consequences, and Treatments of Sleep and Circadian Disruption in the ICU: An Official American Thoracic Society Research Statement

Background: Sleep and circadian disruption (SCD) is common and severe in the ICU. On the basis of rigorous evidence in non-ICU populations and emerging evidence in ICU populations, SCD is likely to have a profound negative impact on patient outcomes. Thus, it is urgent that we establish research priorities to advance understanding of ICU SCD. Methods: We convened a multidisciplinary group with relevant expertise to participate in an American Thoracic Society Workshop. Workshop objectives included identifying ICU SCD subtopics of interest, key knowledge gaps, and research priorities. Members attended remote sessions from March to November 2021. Recorded presentations were prepared and viewed by members before Workshop sessions. Workshop discussion focused on key gaps and related research priorities. The priorities listed herein were selected on the basis of rank as established by a series of anonymous surveys. Results: We identified the following research priorities: establish an ICU SCD definition, further develop rigorous and feasible ICU SCD measures, test associations between ICU SCD domains and outcomes, promote the inclusion of mechanistic and patient-centered outcomes within large clinical studies, leverage implementation science strategies to maximize intervention fidelity and sustainability, and collaborate among investigators to harmonize methods and promote multisite investigation. Conclusions: ICU SCD is a complex and compelling potential target for improving ICU outcomes. Given the influence on all other research priorities, further development of rigorous, feasible ICU SCD measurement is a key next step in advancing the field.

Logistic regression technique is comparable to complex machine learning algorithms in predicting cognitive impairment related to post intensive care syndrome

To evaluate the performance of machine learning (ML) models and to compare it with logistic regression (LR) technique in predicting cognitive impairment related to post intensive care syndrome (PICS-CI). We conducted a prospective observational study of ICU patients at two tertiary hospitals. A cohort of 2079 patients was screened, and finally 481 patients were included. Seven different ML models were considered, decision tree (DT), random forest (RF), XGBoost, neural network (NN), naïve bayes (NB), and support vector machine (SVM), and compared with logistic regression (LR). Discriminative ability was evaluated by area under the receiver operating characteristic curve (AUC), calibration belt plots, and Hosmer-Lemeshow test was used to assess calibration. Decision curve analysis was performed to quantify clinical utility. Duration of delirium, poor Richards-Campbell sleep questionnaire (RCSQ) score, advanced age, and sepsis were the most frequent and important candidates risk factors for PICS-CI. All ML models showed good performance (AUC range: 0.822-0.906). NN model had the highest AUC (0.906 [95% CI 0.857-0.955]), which was slightly higher than, but not significantly different from that of LR (0.898 [95% CI 0.847-0.949]) (P > 0.05, Delong test). Given the overfitting and complexity of some ML models, the LR model was then used to develop a web-based risk calculator to aid decision-making ( https://model871010.shinyapps.io/dynnomapp/ ). In a low dimensional data, LR may yield as good performance as other complex ML models to predict cognitive impairment after ICU hospitalization.

Rest-Activity Rhythm Fragmentation and Weaker Circadian Strength Are Associated With Cognitive Impairment in Survivors of Acute Respiratory Failure

Background: Survivors of acute respiratory failure (ARF) experience long-term cognitive impairment and circadian rhythm disturbance after hospital discharge. Although prior studies in aging and neurodegenerative diseases indicate actigraphy-estimated rest-activity circadian rhythm disturbances are risk factors for cognitive impairment, it is unclear if this applies to ARF survivors. This study explored the relationships of actigraphy-estimated rest-activity circadian rhythms with cognitive functioning in ARF survivors at 3 months after discharge. Methods: 13 ARF survivors (mean age 51 years and 69% males) completed actigraphy and sleep diaries for 9 days, followed by at-home neuropsychological assessment. Principal component factor analysis created global cognition and circadian rhythm variables, and these first components were used to examine the global relationships between circadian rhythm and cognitive measure scores. Results: Global circadian function was associated with global cognition function in ARF survivors (r = .70, p = .024) after adjusting for age, education, and premorbid cognition. Also, greater fragmented rest-activity circadian rhythm (estimated by intradaily variability, r = .85, p = .002), and weaker circadian strength (estimated by amplitude, r = .66, p = .039; relative strength, r = .70, p = .024; 24-h lag serial autocorrelation, r = .67, p = .035), were associated with global cognition and individual cognitive tests. Conclusions: These results suggest circadian rhythm disturbance is associated with poorer global cognition in ARF survivors. Future prospective research with larger samples is needed to confirm these results and increase understanding of the relationship between disrupted circadian rhythms and cognitive impairment among ARF survivors.

Survivorship After Critical Illness and Post-Intensive Care Syndrome

Improvements in critical care medicine have led to a marked increase in survivors of the intensive care unit (ICU). These survivors encounter many difficulties following ICU discharge. The term post -intensive care syndrome (PICS) provides a framework for identifying the most common symptoms which fall into three domains: cognitive, physical, and mental health. There are numerous risk factors for the development of PICS including premorbid conditions and specific elements of ICU hospitalizations. Management is complex and should take an individualized approach with interdisciplinary care. Future research should focus on prevention, identification, and treatment of this unique population.

Exploring the Bidirectional Associations Between Short or Long Sleep Duration and Lower Cognitive Function: A 7-Year Cohort Study in China

Background: Sleep duration is linked to cognitive function, but whether short or prolonged sleep duration results from impaired cognition or vice versa has been controversial in previous studies. We aimed to investigate the bidirectional association between sleep duration and cognitive function in older Chinese participants.

Methods: Data were obtained from a nationally representative study conducted in China. A total of 7984 participants aged 45 years or older were assessed at baseline between June 2011 and March 2012 (Wave 1), 2013 (Wave 2), 2015 (Wave 3), and 2018 (Wave 4). Nocturnal sleep duration was evaluated using interviews. Cognitive function was examined via assessments of global cognition, including episodic memory, visuospatial construction, calculation, orientation and attention capacity. Latent growth models and cross-lagged models were used to assess the bidirectional association between sleep duration and cognitive function.

Results: Among the 7,984 participants who were followed in the four waves of the study, the baseline mean (SD) age was 64.7 (8.4) years, 3862 (48.4%) were male, and 6453 (80.7%) lived in rural areas. Latent growth models showed that both sleep duration and global cognition worsened over time. Cross-lagged models indicated that short or long sleep duration in the previous wave was associated with lower global cognition in the subsequent wave (standardized β = −0.066; 95% CI: −0.073, −0.059; P < 0.001; Wave 1 to 2) and that lower global cognition in the previous wave was associated with short or long sleep duration in the subsequent wave (standardized β = −0.106; 95% CI: −0.116, −0.096; P < 0.001; Wave 1 to 2).

Conclusion: There was a bidirectional association between sleep duration and cognitive function, with lower cognitive function having a stronger association with long or short sleep duration than the reverse relationship. Global cognition was likely the major driver in these reciprocal associations.

Administration of pharmacological sleep aids prior to, during and following critical illness

BACKGROUND

Sleep in the intensive care unit (ICU) is frequently disturbed and this may have a detrimental effect on recovery.

AIMS

To determine use of pharmacological sleep aids in critically ill patients prior to, during and after ICU admission.

METHODS

We conducted a single-centre period prevalence study of all adult patients admitted to a university-associated adult medical-surgical Intensive Care Unit (ICU) for more than two nights in a three-month period ending September 2019. The major outcome of interest was the proportion of ICU patients who had a pharmacological sleep aid administered prior to, during and after ICU admission. Associations of selected patient variables with sleep aid prescription in the ICU were summarized both as unadjusted univariable comparisons, and as adjusted effect estimates returned by a multivariable logistic regression model.

RESULTS

During the study period, 370 patients met all eligibility criteria. A pharmacological sleep aid was identified prior to hospital admission in 34 patients (9%) and in 62 patients (17%) during ICU admission. Of the 340 ICU survivors, 292 remained in the same hospital. Of these, 96 (33%) received a pharmacological sleep aid at least once during their post-ICU general hospital ward stay. Pre-hospital sleep aid use, male sex, longer ICU admission and higher APACHE III scores were associated with sleep aid prescription in the ICU.

CONCLUSIONS

Pharmacological sleep aids are administered frequently in the ICU with administration increasing substantially after ICU discharge. This article is protected by copyright. All rights reserved.

Baseline sleep as a predictor of delirium after surgical aortic valve replacement: A feasibility study

OBJECTIVE

The goal is to assess the feasibility of conducting unattended (type II) sleep studies before surgical aortic valve replacement (SAVR) to examine the relationship between baseline sleep measures and postoperative delirium.

METHODS

This single-site study recruited 18 of 20 study referrals with aortic stenosis undergoing first lifetime SAVR. Subjects completed a home-based type II sleep study. Delirium was assessed postoperative days 1-5. Exact logistic regression was used to determine whether sleep efficiency or apnea/hypopnea index predicts delirium.

RESULTS

Of 18 study participants, 15 successfully completed a home sleep study (mean age: 71.7 +/- 8.1 years old; 10 male subjects). Five subjects (33.3%) developed delirium. Preliminary analyses found that greater sleep efficiency was associated with a large reduction in delirium odds but was not statistically significant (OR = 0.31, 95% CI: 0.06, 1.03, p = 0.057). The point estimate of the relationship between apnea/hypopnea index and delirium was not similarly sizeable (OR 1.10, 95% CI: 0.35, 3.37, p = 0.85).

CONCLUSIONS

Our findings suggest that home type II sleep studies before SAVR are feasible, and they support adequately powered studies investigating type II home sleep studies as a predictor of postoperative delirium and other important postsurgical outcomes.

The Feasibility and Validity of Objective and Patient-Reported Measurements of Cognition During Early Critical Illness Recovery

BACKGROUND

Cognitive outcomes are an important determinant of quality of life after critical illness, but methods to assess early cognitive impairment and cognition recovery are not established. The objective of this study was to assess the feasibility and validity of objective and patient-reported cognition assessments for generalized use during early recovery from critical illness.

METHODS

Patients presented from the community with acute onset of either intracerebral hemorrhage (ICH) or sepsis as representative neurologic and systemic critical illnesses. Early cognitive assessments comprised the Glasgow Coma Scale (GCS), three NIH Toolbox cognition measures (Flanker Inhibitory Control and Attention Test, List Sorting Working Memory Test and Pattern Comparison Processing Speed Test) and two Patient Reported Outcomes Measurement Information System (PROMIS) cognition measures (Cognition-General Concerns and Cognition-Abilities) performed seven days after intensive care unit discharge or at hospital discharge, whichever occurred first.

RESULTS

We enrolled 91 patients (53 with sepsis, 38 with ICH), and after attrition principally due to deaths, cognitive assessments were attempted in 73 cases. Median [interquartile range] Sequential Organ Failure Assessment scores for patients with sepsis was 7 [3, 11]. ICH cases included 13 lobar, 21 deep and 4 infratentorial hemorrhages with a median [IQR] ICH Score 2 [1, 2]. Patient-reported outcomes were successfully obtained in 42 (58% overall, 79% of sepsis and 34% of ICH) patients but scores were anomalously favorable (median 97th percentile compared to the general adult population). Analysis of the PROMIS item bank by four blinded, board-certified academic neurointensivists revealed a strong correlation between higher severity of reported symptoms and greater situational relevance of the items (ρ = 0.72, p = 0.002 correlation with expert item assessment), indicating poor construct validity in this population. NIH Toolbox tests were obtainable in only 9 (12%) patients, all of whom were unimpaired by GCS (score 15) and completed PROMIS assessments. Median scores were 5th percentile (interquartile range [2nd, 9th] percentile) and uncorrelated with self-reported symptoms. Shorter intensive care unit length of stay was associated with successful testing in both patients with ICH and sepsis, along with lower ICH Score in patients with ICH and absence of premorbid dementia in patients with sepsis (all p < 0.05).

CONCLUSIONS

Methods of objective and patient-reported cognitive testing that have been validated for use in patients with chronic medical and neurologic illness were infeasible or yielded invalid results among a general sample of patients in this study who were in early recovery from neurologic and systemic critical illness. Longer critical illness duration and worse neurocognitive impairments, whether chronic or acute, reduced testing feasibility.

Abnormal Sleep, Circadian Rhythm Disruption, and Delirium in the ICU: Are They Related?

Delirium is a syndrome characterized by acute brain failure resulting in neurocognitive disturbances affecting attention, awareness, and cognition. It is highly prevalent among critically ill patients and is associated with increased morbidity and mortality. A core domain of delirium is represented by behavioral disturbances in sleep-wake cycle probably related to circadian rhythm disruption. The relationship between sleep, circadian rhythm and intensive care unit (ICU)-acquired delirium is complex and likely bidirectional. In this review, we explore the proposed pathophysiological mechanisms of sleep disruption and circadian dysrhythmia as possible contributing factors in transitioning to delirium in the ICU and highlight some of the most relevant caveats for understanding the relationship between these complex phenomena. Specifically, we will (1) review the physiological consequences of poor sleep quality and efficiency; (2) explore how the neural substrate underlying the circadian clock functions may be disrupted in delirium; (3) discuss the role of sedative drugs as contributors to delirium and chrono-disruption; and, (4) describe the association between abnormal sleep-pathological wakefulness, circadian dysrhythmia, delirium and critical illness. Opportunities to improve sleep and readjust circadian rhythmicity to realign the circadian clock may exist as therapeutic targets in both the prevention and treatment of delirium in the ICU. Further research is required to better define these conditions and understand the underlying physiologic relationship to develop effective prevention and therapeutic strategies.