Dealing with Delirium: the Importance of Good Sleep

Delirium is defined as a sudden disturbance in attention, awareness, and cognition and is a common, and serious surgical complication amongst the older adult population. It is significantly correlated with adverse clinical outcomes including increased mortality and the loss of independence. The Thesis consists of 5 Chapters and includes a systematic review, a sleep deprivation and a clinical study. The systematic review aims to bridge the gap in sleep screening methodologies by evaluating the use of subjective screening tools and providing recommendations for the use of each tool for researchers and clinicians. Following a review of 25 studies, results were summarised and the needs for researchers and clinicians were considered. For sleep disorders, researchers were recommended to use the Insomnia Severity Index, the Observational Sleep Assessment Instrument (OSAI), the Mayo Sleep Questionnaire and the Sleep Symptom Checklist (SSC), and for clinicians the Insomnia Severity Index, the Observation-based Nocturnal Sleep Inventory, the OSAI, the Mayo Sleep Questionnaire, and the Sleep Interview. The review recommends the use of the Insomnia Severity Index, the OSAI, and Mayo Sleep Questionnaire for both researchers and clinicians. When screening for sleep behaviours and disturbances both researchers and clinicians are recommended to use one of the following include the Pittsburgh Sleep Quality Index, and the Karolinska Sleepiness Scale. This systematic review provides novel guidance and has potential to be incorporated into routine assessments. Older adults are at an increased risk of developing sleep disorders and experience poorer sleep quality, often left untreated due to lack of routine screening, and research has identified sleep disruption to be a risk factor for post-operative delirium. There is potential for patient care to be improved through addressing these underlying sleep disorders, effectively monitoring for changes to sleep quality, and identifying those at greater risk of post-operative delirium as a result. The first study explored the interaction a 24-hour period of sleep deprivation has on the sleep/wake cycle and the effects of the increasing pressure to sleep on changes to attention, psychoticlike symptoms, sleepiness, memory, emotion and scores on a validated delirium assessment scale in healthy adults. The increasing pressure to sleep was found to induce reversible changes in a non-clinical population across the 7 assessments that took place over the 24-hour study duration. Participants become faster at completing the reaction time task, made more mistakes through incorrectly suppressing their responses, exhibited greater variability in reaction time, experienced changes in feelings of delusional thinking, anhedonia, paranoia, positive emotion, as well as presented with iv fluctuating delirium scores. Our study observed similar attentional deficits previously reported in postoperative delirium, namely changes in reaction time and intra-trial variability, during periods participants should normally be awake. The study was able to detect acute changes in cognitive functioning and provides an alternative perspective on delirium assessment. We observed cognitive deficits appearing relatively quickly following several hours of disruptions to the sleep/wake cycle in our young, healthy adult sample without predisposing factors for delirium. Our findings highlight the importance of further exploring the modifiable factor of sleep disruption to reduce delirium risk, particularly in older adults who are at a greater risk of developing delirium. In the clinical study, sleep disruption within a clinical population was explored with the aim of investigating pre- and post-operative sleep, as measured using actigraphy monitors, an objective measure of sleep, and delirium, where the pre-operative baseline for sleep is taken at home. A cohort of 45 older adults undergoing elective hip or knee replacement surgery were enrolled into the study. Assessments took place at baseline, 1-day post-surgery, 4-days post-surgery and 3-months post-surgery. The actigraphy data obtained provided an insight into the quality and quantity of sleep achieved in those awaiting and having recently undergone surgery. General comparisons were made and participants were found to have experienced changes to their normal habitual sleep, through spending less time in bed, less time asleep, and sleeping for a shorter period of time in hospital when compared to their sleep at home. Moreover, participants who experienced an increase in their activity levels and an increase in the amount of time spent awake when they were awoken, were associated with an increase in delirium at 1-day and 4-day post-surgery. The greater degree of change to activity level and average awakening length, the greater the risk of post-operative delirium. Our findings have identified additional sleep measures which increase the risk of post-operative delirium, as well as adding to our knowledge and understanding of sleep disruption in the hospital environment. This supports the importance of sleep, particularly sleep that occurs at home prior to hospitalisation for delirium risk. This has potential implications for improving routine care. Interventions that reduce sleep disruption during periods patients normally sleep may improve sleep quality and in turn reduce delirium risk. The routine monitoring of changes to sleep is recommended to identify those who develop a greater risk of delirium during hospitalisation. This Thesis contributes to the literature on sleep and delirium, providing recommendations for the use of screening tools, which should form a part of regular routine healthcare management. Specific types of sleep disruption that occur prior to and during hospitalisation were identified to increase the v risk of post-operative delirium and has important implications for patient care. A pre-hospitalisation routine for elective surgery should include maintaining good sleep habits to reduce delirium risk.