Leon Lack

Leon Lack
Flinders University · School of Psychology

PhD

About

271
Publications
114,094
Reads
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7,815
Citations
Citations since 2017
128 Research Items
4080 Citations
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20172018201920202021202220230200400600800
20172018201920202021202220230200400600800
Introduction
Circadian Rhythm Period Length in Delayed Sleep Phase Disorder, Treatment of Delayed Sleep Phase Disorder with melatonin administration, Caffeine Withdrawal long term effects,
Additional affiliations
January 1972 - present
Flinders University
Position
  • Professor
Education
February 1965 - December 1971
University of Adelaide
Field of study
  • Psychology
September 1960 - December 1964
Stanford University
Field of study
  • Engineering, neurophysiology, and Psychology

Publications

Publications (271)
Article
Full-text available
Introduction In response to the high incidence of fatigue-based vehicle accidents, roadside assessments of sleepiness are in significant demand. For this purpose, we’ve piloted the existing NeuroFlex® Platform, which takes ocular performance measurements of both prosaccade and antisaccade eye-movements using a portable Virtual Reality (VR) headset....
Article
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Introduction Cognitive behavioural therapy for insomnia (CBT-I) is the recommended treatment for insomnia and improves insomnia symptoms. However, CBT-I effects on sleep-wake state discrepancy have not previously been examined in a sample of individuals with co-morbid insomnia and sleep apnoea (COMISA). This randomised controlled trial investigated...
Article
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The mechanism responsible for the ubiquitous NREM/REM sleep cycles of approximately 90-min period length in humans remains largely unknown. It was originally said to be a product of the 90-minute Basic-Rest-Activity-Cycle (BRAC) assumed to pervade throughout sleep and wakefulness. However, the evidence for the existence of the BRAC during wakefulne...
Article
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Introduction Chronic insomnia negatively impacts quality of life for millions of Australians. Most people with insomnia do not receive the recommended treatment Cognitive Behavioural Therapy for insomnia (CBTi), and many are prescribed sedative-hypnotic medications. This study aims to better understand the help seeking behaviours of people with ins...
Article
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Introduction Sustained vigilance is essential for safety in high-risk workplaces, making rapid and accessible alertness failure vulnerability assessments extremely desirable. We are piloting existing technology, the NeuroFlex® Platform, which takes ocular performance measurements of both prosaccade and antisaccade eye-movements using a portable Vir...
Article
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Introduction Shift-work results in misalignment between circadian timing and the sleep/wake schedule, negatively impacting sleep and performance. In encapsulated environments (e.g., submarines), the lack of strong daily lighting cues impairs circadian entrainment. This study tested whether circadian-informed LED lighting promotes greater circadian...
Article
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Introduction Clinical guidelines for the treatment of insomnia recommend Cognitive Behavioural Therapy for insomnia (CBTi) as the first-line treatment, ideally provided by a psychologist. However, previous research shows most people with insomnia are not referred to a psychologist, and many are prescribed sedative-hypnotic medicines. This study sur...
Article
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Introduction Individuals with chronic insomnia often self-report more wakefulness and less sleep than is derived from objective measures, which is called sleep-wake state discrepancy (SWSD). This study investigated associations between SWSD and clinical characteristics in older adults with sleep maintenance insomnia before and after Cognitive Behav...
Article
Comorbid insomnia and sleep apnea (COMISA) is a highly prevalent and debilitating condition that is more difficult to treat compared with insomnia alone or sleep apnea alone. Approximately 30% to 50% of sleep clinic patients with sleep apnea report comorbid insomnia symptoms. Comorbid insomnia is associated with lower adherence to positive airway p...
Article
Research with ‘good sleepers’ is ubiquitous, yet there are no standardised criteria to identify a ‘good sleeper’. The present study aimed to create and validate a questionnaire for identifying good sleepers for use in research studies known as the Good Sleeper Scale‐15 items (GSS‐15). Data were derived from a population‐based survey of Australian a...
Article
Chronic insomnia is a debilitating condition affecting about 10-15% of the Australian adult population (The American Academy of Sleep Medicine, 2014; American Psychiatric Association, 2013; Appleton et al., 2022; Ohayon, 2002). It is associated with reduced quality of life, daytime impairments like fatigue, irritability and poor mood, and increased...
Article
Light is a potent circadian entraining agent. For many people, daily light exposure is fundamentally dysregulated with reduced light during the day and increased light into the late evening. This lighting schedule promotes chronic disruption to circadian physiology resulting in a myriad of impairments. Developmental changes in sleep-wake physiology...
Article
Objective Although clinical guidelines recommend Cognitive Behavioural Therapy for insomnia (CBTi) as the first-line treatment for insomnia, many people with insomnia do not have access to CBTi and are prescribed sedative-hypnotic medicines by medical health professionals. Psychologists have training in CBT and may be well placed to deliver behavio...
Article
Study Objectives Carefully controlled studies of wind turbine noise (WTN) and sleep are lacking, despite anecdotal complaints from some residents in wind farm areas and known detrimental effects of other noises on sleep. This laboratory-based study investigated the impact of overnight WTN exposure on objective and self-reported sleep outcomes. Met...
Article
Full-text available
Study objectives: In most standardized approaches to cognitive behavioral therapy for insomnia (CBT-I), it is commonly the case that total wake time reduces substantially during sleep restriction, but self-reported total sleep time (TST) is minimally affected. By follow-up, however, TST increases by almost 1 hour on average. A secondary analysis w...
Article
Full-text available
People with insomnia frequently underestimate the duration of their sleep compared to objective polysomnography measured sleep duration. Cognitive behavioural therapy for insomnia (CBT-I) is the most effective treatment for insomnia and also reduces the degree of sleep underestimation. Obstructive sleep apnoea (OSA) is a highly prevalent sleep diso...
Article
Insomnia and obstructive sleep apnoea (OSA) commonly co-occur (COMISA), and their cooccurrence has been associated with worse cardio-metabolic and mental health. However, it remains unknown if people with COMISA are at a heightened risk of incident cardiovascular events. This study used longitudinal data from the Sleep Heart Health Study (N=5,803)...
Article
Study objectives: Intensive sleep retraining (ISR) is a behavioral treatment that involves a patient falling asleep repeatedly over 1 treatment session (< 24 hours in duration) to treat sleep-onset insomnia. ISR relies on high homeostatic sleep and circadian rhythm drives to facilitate rapid sleep onsets overnight. The high cost and inaccessibilit...
Article
Study objectives: This pilot study aimed to investigate differences in the semantic meanings that individuals attribute to the words "sleepy," "fatigued," "tired," and "drowsy." Methods: Ninety-six undergraduate students ranked the target words on three independent dimensions (Evaluative, Potency, and Activity) to assess their meaning using the...
Article
Key points • Approximately 30-50% of patients with obstructive sleep apnea (OSA) in sleep clinics report co-morbid insomnia symptoms. • Patients with co-morbid insomnia and sleep apnea (COMISA) have worse sleep, mental health, physical health, and quality of life, compared to patients with either insomnia or sleep apnea alone. • Patients with COMIS...
Article
Study Objectives Increased mortality has been reported in people with insomnia and in those with obstructive sleep apnoea (OSA). However, these conditions commonly co-occur and the combined effect of co-morbid insomnia and sleep apnoea (COMISA) on mortality risk is unknown. This study used Sleep Heart Health Study (SHHS) data to assess associations...
Article
Study Objectives Wind turbine noise exposure could potentially interfere with the initiation of sleep. However, effects on objectively assessed sleep latency are largely unknown. This study sought to assess the impact of wind turbine noise on polysomnographically-measured and sleep diary-determined sleep latency compared to control background noise...
Article
Wind turbine noise is dominated by low frequencies for which effects on sleep relative to more common environmental noise sources such as road traffic noise remain unknown. This study examined the effect of wind turbine noise compared with road traffic noise on sleep using quantitative electroencephalogram power spectral analysis. Twenty‐three part...
Article
Full-text available
Introduction Insomnia is the most common sleep disorder, 10–30% of adults have regular difficulties falling and/or staying asleep that cause significant daytime impairments. General Practitioner (GP) clinical guidelines recommend Cognitive Behavioural Therapy for insomnia (CBTi) as the first-line treatment rather than medications. However, most GPs...
Article
Full-text available
Introduction Good sleep is not merely the absence of sleep disorder symptoms, yet this criterion is commonly applied in research studies. We developed the Good Sleeper Scale-13 (GSS-13) to standardise identification of good sleepers. Methods We conducted a secondary analysis of the 2019 Sleep Health Foundation online survey of adult Australians (N...
Article
Full-text available
Introduction Past research and our own has not shown a differential response to Cognitive Behaviour Therapy for insomnia (CBTi) based on objective sleep duration. It is valuable to investigate CBTi responsiveness is a function of objective sleep efficiency (SE) instead of objective sleep duration. This study is a secondary exploratory analysis of o...
Article
Full-text available
Introduction Well-controlled studies of wind farm noise (WFN) on sleep are lacking despite complaints and known effects of other noise types on sleep. This laboratory-based study investigated the impact of continuous full-night WFN exposure replicated from field recordings on polysomnography-measured (objective) and sleep diary-determined (subjecti...
Article
Full-text available
Introduction Co-morbid insomnia and sleep apnoea (COMISA) is a highly prevalent and debilitating condition. Previous studies have investigated associations between insomnia and mortality, and OSA and mortality, but not COMISA. Thus, this study investigated associations between OSA, insomnia and COMISA on mortality and cardiovascular event risks. M...
Article
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Introduction Total sleep time (TST) does not exceed baseline for the majority of patients after CBT-I. However by follow-up, TST increases by almost 1 hour on average. The current study investigated the extent to which this TST improvement is common and assessed for baseline predictors of increased TST after CBT-I. Methods This study is an archiva...
Article
Full-text available
Introduction Co-morbid insomnia and sleep apnoea (COMISA) is a prevalent and debilitating condition that is difficult to treat. COMISA patients have lower average adherence to continuous positive airway pressure (CPAP) therapy compared to patients with sleep apnoea alone. However, a sub-sample of COMISA patients may show adequate CPAP use that impr...
Article
Full-text available
Introduction Chronic insomnia is a common sleep disorder, with an estimated 15% of Australian adults reporting symptoms of insomnia. Australian general practitioner (GP) guidelines recommend cognitive behavioural therapy for insomnia (CBTi) as first-line treatment for insomnia however research suggests that GPs instead rely heavily on sleep hygiene...
Article
Full-text available
Introduction The prevalence of sleep difficulties from wind farm noise (WFN) compared to road traffic noise (RTN) or other sources is unknown. This study investigated the prevalence, severity and source of sleep difficulties in WFN, RTN and quiet rural exposure areas. Methods Geographic sampling and computer assisted telephone interviews were used...
Article
Full-text available
Introduction This study used ambulatory sleep studies to examine potential relationships between wind farm sound pressure level ([SPL] in dBA) and amplitude modulation (AM) on conventional measures of sleep quality in individuals residing within 10 km of a wind turbine in Australia. Methods Twenty six individuals (42:58%, females:males) aged (mean...
Article
Managing insomnia in general practice • GPs can use the Sleep Condition Indicator to assess for insomnia • Insomnia can be an acute (<3 months) or chronic disorder (≥3 months) • Cognitive Behavioural therapy for Insomnia (CBTi) is the most effective treatment for chronic insomnia • GPs can administer a Brief Behavioural Therapy for Insomnia (BBTi)...
Article
Background Evidence regarding the association between perinatal smoking and insomnia symptoms in adulthood is limited. Using the UK 1970 Birth Cohort Study, we determined the association of maternal smoking during pregnancy and early-childhood with insomnia symptoms at 42 years. Methods Participants were followed from birth (1970; N = 9020; male,...
Conference Paper
Introduction: Co-morbid insomnia and sleep apnoea (COMISA) is a prevalent and debilitating condition that is difficult to treat. People with COMISA have lower average adherence to continuous positive airway pressure (CPAP) therapy compared to patients with sleep apnoea alone. However, a sub-sample of people with COMISA may show adequate CPAP use...
Article
Full-text available
Background Chronic insomnia is a highly prevalent disorder, with ten to thirty percent of Australian adults reporting chronic difficulties falling asleep and/or staying asleep such that it causes significant daytime impairment. Current Australian general practice guidelines recommend cognitive behavioural therapy for insomnia (CBTi) as first line t...
Article
Insomnia and obstructive sleep apnea (OSA) commonly co-occur. Approximately 30-50% of patients with OSA report clinically significant insomnia symptoms, and 30-40% of patients with chronic insomnia fulfil diagnostic criteria for OSA. Compared to either insomnia or OSA alone, co-morbid insomnia and sleep apnea (COMISA) is associated with greater mor...
Article
Background: Insomnia is a prevalent and debilitating disorder commonly managed by family physicians. Insomnia guidelines recommend cognitive behavioral therapy for insomnia (CBTi) as the ‘first-line’ treatment. However, family physicians report limited time, knowledge, access, support, and referral options to manage patients with CBTi. Consequently...
Article
Full-text available
Methods for predicting circadian phase have been developed for healthy individuals. It is unknown whether these methods generalize to clinical populations, such as delayed sleep–wake phase disorder (DSWPD), where circadian timing is associated with functional outcomes. This study evaluated two methods for predicting dim light melatonin onset (DLMO)...
Article
• Depression and insomnia commonly co-occur, resulting in greater morbidity for patients, and difficult diagnostic and treatment decisions for clinicians. • When patients report symptoms of both depression and insomnia, it is common for medical practitioners to conceptualise the insomnia as a ‘secondary symptom’ of depression. This implies that th...
Article
Full-text available
Objective: Co-morbid insomnia and sleep apnea (COMISA) is a common and debilitating condition that is more difficult to treat compared to insomnia or sleep apnea-alone. Emerging evidence suggests that cognitive behavioral therapy for insomnia (CBTi) is effective in patients with COMISA, however those with more severe sleep apnea and evidence of gre...
Article
Introduction: Insomnia and obstructive sleep apnoea (OSA) are the two most prevalent sleep disorders, and frequently co-occur (COMISA) in sleep clinic samples. However, few studies have investigated the prevalence or associations of COMISA in the general population. Methods: We used population-based online survey data from 2,044 Australian adults....
Article
Although there is growing recognition of the effects of living with sleep disorders and the important role of primary care in their identification and management, studies indicate that the detection of sleep apnoea (OSA) and insomnia may still be low. This large representative community-based study (n=2977 adults) used logistic regression models to...
Article
Full-text available
Daytime impairments feature in the diagnostic criteria for insomnia disorder yet are rarely assessed comprehensively in clinical practice and tend to focus on mood and subjective assessment of cognitive competence. In order to gain more information about the engagement in daily activities we developed the Sleep Impact on Activity Diary (SIAD). This...
Article
Full-text available
Study Objectives: THIM is a wearable device designed to accurately estimate sleep onset. This article presents two studies that tested the original (Study 1) and a refined (Study 2) THIM sleep onset algorithms compared to polysomnography (PSG). Methods: Twelve (Study 1) and twenty (Study 2) individuals slept in the laboratory on two nights where p...
Article
Full-text available
Introduction: THIM is a new wearable device worn on the finger that can passively monitor sleep and wakefulness overnight using actigraphy. This article showcases the development of the THIM sleep tracking algorithm (Study 1), and the testing of its accuracy against polysomnography (PSG) with an independent sample of good and poor sleepers (Study 2...
Preprint
Full-text available
Background Chronic insomnia is a highly prevalent disorder, with ten to thirty percent of Australian adults reporting chronic difficulties falling asleep and/or staying asleep such that it causes significant daytime impairment. Current Australian general practice guidelines recommend Cognitive Behavioural Therapy for insomnia (CBTi) as first line t...
Article
Little is known about the potential impacts of wind turbine noise (WTN) on sleep. Previous research is limited to cross‐sectional studies reporting anecdotal impacts on sleep using inconsistent sleep metrics. This meta‐analysis sought to comprehensively review studies evaluating the impact of WTN using widely accepted and validated objective and su...
Article
Study objectives Compare the degree of sleep misestimation in older adults with insomnia presenting with objectively short relative to normal sleep duration, and investigate the differential therapeutic response on sleep misestimation between the proposed sleep duration phenotypes to Cognitive Behaviour Therapy for insomnia (CBTi) Method Ninety-on...
Article
Full-text available
Research has indicated that individuals with certain traits may be better suited to shiftwork and non-standard working arrangements. However, no research has investigated how individual differences impact on-call outcomes. As such, this study investigated the impact of trait anxiety on sleep and performance outcomes on-call. Seventy male participan...
Article
Full-text available
Behavioural responses to auditory stimuli cease in late N1 or early N2 sleep. Yet, responsiveness to minimal intensity tactile stimuli and the correspondence with sleep microstructure during the sleep onset period is unknown. The aim of the present study was to investigate sleep microstructure using quantitative electroencephalography analysis when...
Article
Insomnia is a common disorder managed in Australian general practice. The RACGP recommends cognitive and behavioural therapy for insomnia (CBTi) strategies as the first-line treatment. There are multiple simple and effective CBTi options accessible to Australian general practitioners and patients, but these are often underused.
Article
Study Objectives: Patients with co-morbid insomnia and sleep apnea (COMISA) report increased severity of depression, anxiety, and stress symptoms compared to patients with either insomnia or sleep apnea alone. Although cognitive behavioral therapy for insomnia (CBTi) is an effective treatment for COMISA, previous research suggests a reduced respons...
Article
Study objectives: Myopia, or near-sightedness, is the most common refractive vision disorder and predisposes the eye to many blinding conditions in adulthood. Recent research has suggested that myopia is associated with increased endogenous melatonin production. Here we investigated the differences in melatonin circadian timing and output in young...
Article
Although cognitive behavioural therapy for insomnia (CBTi) is the recommended ‘first-line’ treatment for insomnia, most patients are initially treated with sedative-hypnotic medications. Given the risk of impaired cognitive and psychomotor performance, serious adverse events, and long-term dependence associated with sedative-hypnotics, guidelines r...
Article
SHORT OVERVIEW Insomnia is a common disorder managed in Australian general practice. The RACGP recommend cognitive and behavioural therapy for insomnia (CBTi) strategies as the ‘first line’ treatment. There are multiple simple and effective CBTi options currently accessible to Australian general practitioners and patients, but these are often under...
Article
Background On-call working arrangements have been shown to negatively impact sleep. However, workers may perceive their sleep to be worse than it actually is. The aim of this study was to compare participants’ pre- and post-sleep estimates of sleep duration and sleep quality with objectively measured sleep when on-call under laboratory conditions....
Article
Background: Co-occurring insomnia and symptoms of depression, anxiety and stress pose difficult diagnostic and treatment decisions for clinicians. Cognitive Behavioral Therapy for Insomnia (CBTi) is the recommended first-line insomnia treatment, however symptoms of depression, anxiety and stress may reduce the effectiveness of CBTi. We examined the...
Article
Background: Chronic insomnia is a prevalent and debilitating disorder managed in Australian general practice. The most effective and recommended first-line treatment for insomnia is cognitive behavioural therapy. This treatment has also been translated to a condensed brief behavioural therapy for insomnia (BBTi) which is suitable for delivery in th...
Article
We examined whether a polymorphism of the PERIOD3 gene (PER3; rs57875989) modulated the sleep promoting effects of melatonin in Delayed Sleep‐Wake Phase Disorder (DSWPD). One hundred and four individuals (53 males; 29.4±10.0 years) with DSWPD and a delayed dim light melatonin onset (DLMO) collected buccal swabs for genotyping (PER34/4 n=43; PER3 5...
Article
Study Objectives We investigated biological and behavioural rhythm period lengths (i.e., taus) of Delayed Sleep-Wake Phase Disorder (DSWPD) and Non-24-Hour Sleep-Wake Rhythm Disorder (N24SWD). Based on circadian phase timing (temperature and dim light melatonin onset), DSWPD participants were dichotomised into a circadian-delayed and a circadian no...
Article
Cognitive behavioural therapy for insomnia (CBT-I) is a promising intervention with established efficacy, yet evidence of its cost-effectiveness remains unclear. Systematic searches were conducted in Medline, Psychinfo, ProQuest, Cochrane, Scopus, CINAHL, Web of Science and Emcare. Titles and abstracts were screened against eligibility criteria, an...
Presentation
Introduction THIM is a new ring-like sleep device that, if found to accurately measure sleep onset, could be used for a variety of clinical purposes. These include administering a brief but effective treatment for insomnia called Intensive Sleep Retraining, facilitating the optimal 10-minute power nap, and administering Multiple Sleep Latency Tests...
Presentation
Introduction THIM is a new consumer ring-like device that can passively monitor sleep overnight using actigraphy. This project aimed to develop the THIM sleep tracking algorithm (Study 1), and test its accuracy against polysomnography (PSG) with another independent sample of good and poor sleepers (Study 2). Methods Study 1: 25 healthy individuals...
Article
Full-text available
Insomnia and obstructive sleep apnoea (OSA) frequently co-occur and may be causally related through sleep fragmentation and/or hyperarousal mechanisms. Previous studies suggest that OSA treatment can improve insomnia severity. However, the effect of insomnia treatment on OSA severity has not been investigated. We performed a randomised controlled t...
Article
Full-text available
Introduction: Abnormal rapid eye movement (REM) sleep is often symptomatic of chronic disorders, however polysomnography, the gold standard method to measure REM sleep, is expensive and often impractical. Attempts to develop cost-effective ambulatory systems to measure REM sleep have had limited success. As elevated twitching is often observed dur...
Article
Full-text available
Study Objectives While cognitive and behavioral therapy for insomnia (CBTi) is an effective treatment in patients with co-morbid moderate and severe obstructive sleep apnea (OSA), there is concern that the bedtime restriction component of CBTi might dangerously exacerbate daytime sleepiness in such patients. We examined randomized controlled trial...
Article
Full-text available
ABSTRACT:Co-morbid insomnia and sleep apnea (COMISA) is a highly prevalent and debilitating disorder, which results in additive impairments to patients’ sleep, daytime functioning, and quality of life, and complex diagnostic and treatment decisions for clinicians. Although the presence of COMISA was first recognised by Christian Guilleminault and c...
Article
Full-text available
Introduction: Co-morbid Insomnia and Sleep Apnea (COMISA) is a highly prevalent and debilitating disorder, which is more difficult to treat compared to the presentation of either disorder alone. Different insomnia subtypes in COMISA (initial, middle, and late) may reflect different underlying mechanisms, which require different treatment approaches...