Sleep inertia and alcohol impairment in young adults: Neurocognitive effects and interactions Implications for fire escape behaviours Melanie Joy Tokley, BPsyc(Hons) Submitted in partial fulfilment of the requirements of the degree of Doctor of Psychology (Clinical Neuropsychology) School of Social Sciences & Psychology Victoria University, Melbourne AUSTRALIA June 2009 ABSTRACT Alcohol intoxication is known to considerably increase the probability of death from fire across the lifespan, to the extent that it has been isolated as the single most significant risk factor. The study investigated the combined effects of sleep inertia and alcohol impairment on fire emergency-relevant cognitive performance indicators in a young adult population. Mental tracking, visual scanning, psychomotor speed, working memory and sustained, selective, and divided attention functions were assessed for performance decrements and reference to speed-accuracy trade-off effects. Participants were 24 young adults (18-26 years) who participated in a repeated-measures study over 2 non- consecutive nights; 1 night with alcohol administration and 1 ‘sober’ night. During the alcohol administration night, 10-minute testing blocks occurred under (1) baseline sober and (2) baseline 0.05 blood alcohol concentration (BAC) conditions. Subsequently, subjects were awoken from stage 4 sleep and assessed in two consecutive 10-minute blocks (3) and (4). Self-reports of sleepiness and clearheadedness were also taken. The same procedure was used during the sober night (with condition (2) excluded). All cognitive functions assessed showed an alcohol effect (i.e., decrements between sober baseline (1) and conditions of alcohol (2)), and an even larger sleep inertia effect (i.e., greater decrements between sober baseline (1) and conditions of sleep inertia alone (3) and (4)). Sleep inertia selectively affected performance speed on the working memory task, whilst performance accuracy on this task was affected by conditions of alcohol impairment only. When the sober and alcohol nights were compared, there was no combined or synergistic interaction between sleep inertia and alcohol impairment on the cognitive tasks or subjective measures during the first 10 minutes of sleep inertia. Conditions of combined sleep inertia and alcohol impairment produced cognitive performance decrements that were greater than those produced by alcohol administration alone, but not those produced by sleep inertia alone. Indeed, sleep inertia effects appeared to ‘override’ alcohol effects. At 10-20 minutes post-awakening, however, sleep inertia effects began to dissipate, thus ‘unmasking’ alcohol effects on some tasks, including accuracy of working memory performance, selective/sustained attention and subjective sleepiness. Divided attention performance demonstrated a complex and ii unpredictable pattern at 10-20 minutes post-awakening whereby performance under conditions of sleep inertia and alcohol intoxication combined became significantly worse than either condition alone, indicating that alcohol effects were also possibly being unmasked for this measure. Other measures (speed of working memory performance and subjective clearheadedness) showed no difference between conditions at 10-20 minutes post-awakening. The results suggest that (1) moderate alcohol impairment and sleep inertia do not combine to produce further decrements in neurocognitive functioning than those caused by the effects of alcohol or sleep inertia alone and (2) sleep inertia poses a greater risk to fire emergency escape than moderate alcohol impairment. Moreover this data suggests that when awoken abruptly in an emergency situation, prior alcohol consumption to 0.05 BAC will not further impede cognitive functioning that is already compromised by a state of sleep inertia. The study considers the importance of the arousing effects of task complexity, the BAC curve (particularly the descending limb), and speed-accuracy trade-off effects in predicting the effects of sleep inertia and alcohol on cognitive performance. iii DECLARATION I, Melanie Tokley, declare that the Doctor of Psychology (Clinical Neuropsychology) thesis entitled “Sleep inertia and alcohol impairment in young adults: Neurocognitive effects and interactions” is no more than 40,000 words in length, exclusive of tables, figures, appendices, references and footnotes. This thesis contains no material that has been submitted previously, in whole or in part, for the award of any other academic degree or diploma. Except where otherwise indicated, this thesis is my own work. Signature: Date: 9th September 2009 iv ACKNOWLEDGEMENTS This thesis would not have been possible without the support and guidance of my wonderful supervisors Professor Dorothy Bruck and Dr. Michelle Ball. It has been an incredible privilege to work with both of you, thank you for your endless encouragement. I would also like to thank my patient and precious family. Particularly my mum, Louella, who shared in every triumph and tribulation of the writing process and provided much needed optimism when mine almost failed me. Thank you to my Dad, Michael, for the ongoing support and unflagging belief in my abilities. Thank you to my colleagues in the 2006 neuropsychology doctoral intake whose friendship and support has been one of the highlights of my journey through post- graduate study. A special thank you to our course co-ordinator, Dr. Alan Tucker, whose incredible wisdom and mentorship will never be forgotten. Thank you to the participants of this study for their co-operation and enthusiasm, and to the sleep technicians for their assistance and diligence. This research was financially supported by the National Fire Protection Association’s Fire Protection Research Foundation via a grant from the US Fire Administration. The study formed part of a larger research project that was a collaboration between the School of Social Sciences & Psychology and the Centre for Environmental Safety and Risk Engineering (CESARE) at Victoria University. v TABLE OF CONTENTS List of Tables ............................................................................................................... x List of Figures ........................................................................................................... xii List of Appendices ....................................................................................................xiii CHAPTER ONE: INTRODUCTION ........................................................................ 1 1.1 Alcohol and fire ....................................................................................... 2 1.2 Aims ......................................................................................................... 3 1.3 Problem summary ................................................................................... 4 CHAPTER TWO: LITERATURE REVIEW ............................................................ 5 2.1 Sleep inertia ............................................................................................. 5 2.1.1 Arousal hypothesis .............................................................................. 5 2.1.2 Dinges’ (1990) pressure for sleep model .............................................. 9 2.1.3 Folkard and Åkerstedt’s (1992) three-process model ......................... 10 2.2 Refining the models: The parameters of sleep inertia ......................... 12 2.2.1 Pre-awakening stage of sleep ............................................................. 12 2.2.2 Prior sleep deprivation ....................................................................... 14 2.2.3 Circadian rhythm and time-of-day effects .......................................... 16 2.2.4 Time course of sleep inertia ............................................................... 19 2.2.5 Summary ........................................................................................... 21 2.3 Sleep inertia and neurocognitive functioning ....................................... 22 2.3.1 Working memory .............................................................................. 22 2.3.2 Attention ........................................................................................... 24 2.3.3 Speed-accuracy trade-off effect ......................................................... 27 2.3.4 Simulation studies: Sleep inertia and emergency behaviour ............... 29 2.3.4.1 Effect of arousal and stress on cognitive performance during sleep inertia ...................................................................................................... 32 2.3.4.2 Is sleep inertia the same as sleep deprivation? ........................... 34 2.3.5 Summary ........................................................................................... 36 vi 2.4 Subjective sleepiness and sleep inertia ................................................. 37 2.5 Alcohol ................................................................................................... 38 2.5.1 Alcohol metabolisation ...................................................................... 39 2.5.2 Alcohol and the sleeping brain .......................................................... 39 2.6 Alcohol and sleep ................................................................................... 40 2.6.1 Alcohol and arousal thresholds .......................................................... 45 2.7 Alcohol and neurocognitive functioning ............................................... 46 2.7.1