Publications (9)31.3 Total impact
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Article: At home and away: measuring the sleep of Australian truck drivers.
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ABSTRACT: The causes of fatigue in truck drivers related to work hours have been studied extensively and are reasonably well understood. However, much less is known about how rest opportunities can be structured to optimise recovery from fatigue. The nature of the road transport industry often requires that rest be taken in various locations. New investigation in this area, focusing on sleep obtained in truck cabs and other non-home environments is critically important to complement existing understanding. This study examined sleep at home and in truck cabs, in truck drivers who were actively working during the time of the study. Thirty-seven male drivers aged between 24 and 63 years (age: 48.7 ± 9.0 years; mean ± SD) wore activity monitors (also known as 'sleep watches') and completed work and sleep diaries for a period of 21 days, recording their subjective fatigue levels before, during and after work shifts, and before and after sleep periods. They also self-rated their sleep quality and noted the number of times they woke during sleep periods. Analyses focused on home versus in-truck sleep periods. The subjective data suggested that a greater quantity (P<.001) and quality (P<.05) of sleep was obtained at home than in the truck, and that sleeping at home more effectively reduced fatigue levels (P<.001). The objective data showed trends towards longer sleep length at home, but other variables, including total sleep per 24h and sleep quality, showed no significant differences. This study demonstrates that measuring sleep quantity and quality in operational road transport environments is feasible. The findings caution against over-reliance on laboratory and simulator studies since there are critical aspects of the operating environment that cannot be validly studied in artificially controlled settings. This study is unique in its direct examination of sleep quantity and quality in truck drivers sleeping at home and away from home.Accident; analysis and prevention 03/2012; 45 Suppl:36-40. · 1.65 Impact Factor -
Article: Auditory evoked potentials remain abnormal after CPAP treatment in patients with severe obstructive sleep apnoea.
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ABSTRACT: To assess the effects of 3 months of optimal CPAP treatment on auditory event related potentials (AERP) in patients with severe obstructive sleep apnoea (OSA) compared with healthy controls. Auditory odd-ball related N1, P2, N2 and P3 AERP components were assessed in 9 severe OSA subjects and 9 healthy controls at baseline evaluation and at ∼3 months follow-up in both groups, with OSA subjects treated with continuous positive air-way pressure (CPAP) during this period. Severe OSA subjects showed significantly delayed, P2, N2 and P3 latencies, and significantly different P2 and P3 amplitudes compared to controls at baseline (group effect, all p<0.05). At follow-up evaluation P3 latency shortened in treated OSA patients but remained prolonged compared to controls (group by treatment interaction, p<0.05) despite high CPAP compliance (6h/night). The earlier AERP (P2 and N2) components did not change in either controls or OSA patients at follow-up and remained different in patients versus controls. This study demonstrates that in severe OSA patients AERP responses show minimal or no improvement and remain abnormal following 3 months of optimal CPAP treatment. Persistent cortical sensory processing abnormalities despite treatment in severe OSA may have implications for daytime neurobehavioral performance and safety in OSA patients. AERP responses may help identify residual performance deficits and risks.Clinical neurophysiology: official journal of the International Federation of Clinical Neurophysiology 08/2011; 123(2):310-7. · 3.12 Impact Factor -
Article: Driving simulator performance remains impaired in patients with severe OSA after CPAP treatment.
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ABSTRACT: To assess the effectiveness of CPAP treatment in improving 90-minute driving simulator performance in severe OSA patients compared to age/gender matched controls. Driving simulator performance was assessed at baseline and 3 months later, with OSA patients treated with CPAP during the interval. University Teaching Hospital. Patients with severe OSA (n = 11) and control subjects without OSA (n = 9). CPAP MEASUREMENTS AND RESULTS: Simulator driving parameters of steering deviation, braking reaction time and crashes were measured at baseline and ∼3 months follow-up. At baseline, OSA subjects demonstrated significantly greater steering deviation compared to controls (mean [95% CI], OSA group, 49.9 cm [43.7 to 56.0 cm] vs control group, 34.9 cm [28.1 to 41.7 cm], p = 0.003). Following ∼3 months of CPAP treatment (mean ± SD 6.0 ± 1.4 h/night), steering deviation in OSA subjects improved by an average of 3.1 cm (CI, 1.4 to 4.9), p < 0.001, while no significant steering changes were observed in the control group. Despite the improvement, steering deviation in the OSA group remained significantly higher than in controls (OSA group, 46.7 cm [CI, 40.6 to 52.8 cm] vs control group, 36.1 cm [CI, 29.3 to 42.9 cm], p = 0.025). While driving simulator performance improved after ∼3 months of CPAP treatment with high adherence in patients with severe OSA, performance remained impaired compared to control subjects. These results add to the growing body of evidence that some neurobehavioral deficits in patients with severe OSA are not fully reversed by treatment. Further studies are needed to assess causes of residual driving simulator impairment and to determine whether this is associated with persistent elevated real-life accident risk. Data presented in this manuscript was collected as part of a clinical trial "Experimental Investigations of Driving Impairment in Obstructive Sleep Apnoea" ACTRN12610000009011, http://www.anzctr.org.au/trial_view.aspx?ID=334979Journal of clinical sleep medicine: JCSM: official publication of the American Academy of Sleep Medicine 06/2011; 7(3):246-53. · 3.23 Impact Factor -
Article: Increased rate of traffic law infringements during on‐road metropolitan driving in obstructive sleep apnea patients
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ABSTRACT: The aim of this study was to compare metropolitan on-road driving performance in patients with severe obstructive sleep apnea (OSA) and healthy age-matched controls. A driving assessor–based on-road driving test was performed at 2.00 pm in severe OSA patients and age-matched healthy controls. Main outcome measures included passing or failing the test, occurrence of minor traffic faults (e.g. not indicating, late braking, mirror checking) and traffic law infringements (e.g. failing to stop or give way, speeding). Compared to controls, there was no evidence of gross driving impairment or higher driving test failure rate in OSA patients. However, OSA patients demonstrated ∼60% more traffic law infringements (11.0 ± 1.8 versus 6.8 ± 1.0% of general driving tasks, p= 0.024), primarily reflecting repeated failure to stop at stop signs and/or traffic lights (p= 0.037). Patients with severe OSA break road laws more frequently than age-matched controls during a short city driving test, suggesting greater inattention and thus potentially higher motor vehicle accident risk. Further studies are needed to extend these early findings, which raise serious clinical and road safety concerns.Sleep and Biological Rhythms 06/2011; 9(3):144 - 149. · 0.48 Impact Factor -
Article: Work hours, workload, sleep and fatigue in Australian Rail Industry employees.
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ABSTRACT: Research suggests that less than 5 h sleep in the 24 h prior to work and/or more than 16 h of wakefulness can significantly increase the likelihood of fatigue-related impairment and error at work. Studies have also shown exponential safety declines with time on shift, with roughly double the likelihood of accident or injury after 10 h relative to the first 8h. While it is acknowledged that reduced sleep, increased wakefulness and longer work hours produce work-related fatigue, few studies have examined the impact of workload on this relationship. Studies in the rail industry have focused on drivers. This study investigated fatigue in a large sample of Australian Rail Industry Employees. Participants were from four companies (n = 90: 85m, 5f; mean age 40.2 ± 8.6 y). Data was analysed for a total of 713 shifts. Subjects wore wrist actigraphs and completed sleep and work diaries for 14-days. They also completed the Samn-Perelli Fatigue Scale at the beginning and end of shifts, and the NASA-TLX workload scale at least twice during each shift. Average (±SD) sleep length (7.2 ± 2.6h), prior wake at shift end (12.0 ± 4.7h), shift duration (8.0 ± 1.3) and fatigue (4.1 ± 1.3, "a little tired, less than fresh") were within limits generally considered acceptable from a fatigue perspective. However, participants received 5 h or less sleep in the prior 24 h on 13%, were awake for at least 16 h at the end of 16% and worked at least 10 h on 7% of shifts. Subjects reported that they felt "extremely tired, very difficult to concentrate," or "completely exhausted, unable to function effectively" on 13% of shifts. Sleep length (OR = 0.88, p < 0.01), shift duration (OR = 1.18, p < 0.05), night shift (REF = morning shift, OR = 2.12, p < 0.05) and workload ratings (OR = 1.2, p < 0.05) were significant predictors of ratings of extreme tiredness/exhaustion (yes/no). While on average, sleep loss, extended wakefulness, longer work hours and work-related fatigue do not appear problematic in this sample, there is still a notable percentage of shifts that are likely to be associated with high levels of work-related fatigue. Given the size of the Australian Rail Industry, with thousands of shifts occurring each day, this is potentially of operational concern. Further, results indicate that, in addition to sleep length, wakefulness and work hours, workload significantly influences fatigue. This has possible implications for bio-mathematical predictions of fatigue and for fatigue management more generally.Applied ergonomics 01/2011; 42(2):202-9. · 1.11 Impact Factor -
Article: Effects of alcohol and sleep restriction on simulated driving performance in untreated patients with obstructive sleep apnea.
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ABSTRACT: Because of previous sleep disturbance and sleep hypoxia, patients with obstructive sleep apnea (OSA) might be more vulnerable to the effects of alcohol and sleep restriction than healthy persons. To compare the effects of sleep restriction and alcohol on driving simulator performance in patients with OSA and age-matched control participants. Driving simulator assessments in 2 groups under 3 different conditions presented in random order. Adelaide Institute for Sleep Health, Sleep Laboratory, Adelaide, Australia. 38 untreated patients with OSA and 20 control participants. Steering deviation, crashes, and braking reaction time. Unrestricted sleep, sleep restricted to a maximum of 4 hours, and ingestion of an amount of 40% vodka calculated to achieve a blood alcohol level of 0.05 g/dL. Patients with OSA demonstrated increased steering deviation compared with control participants (mean, 50.5 cm [95% CI, 46.1 to 54.9 cm] in the OSA group and 38.4 cm [CI, 32.4 to 44.4 cm] in the control group; P < 0.01) and significantly greater steering deterioration over time (group by time interaction, P = 0.02). The increase in steering deviation after sleep restriction and alcohol was approximately 40% greater in patients with OSA than in control participants (group by condition interaction, P = 0.04). Patients with OSA crashed more frequently than control participants (1 vs. 24 participants; odds ratio [OR], 25.4; P = 0.03) and crashed more frequently after sleep restriction (OR, 4.0; P < 0.01) and alcohol consumption (OR, 2.3; P = 0.02) than after normal sleep. In patients with OSA, prolonged eye closure (>2 seconds) and microsleeps (> 2 seconds of theta activity on electroencephalography) were significant crash predictors (OR, 19.2 and 7.2, respectively; P < 0.01). Braking reaction time was slower after sleep restriction than after normal sleep (mean, 1.39 [SD, 0.06] seconds vs. 1.22 [SD, 0.04] seconds; P < 0.01) but not after alcohol consumption. No group differences were found. Simulated driving was assessed rather than on-road driving. Patients with OSA are more vulnerable than healthy persons to the effects of alcohol consumption and sleep restriction on various driving performance variables. Australian National Health and Medical Research Council.Annals of internal medicine 10/2009; 151(7):447-55. · 16.73 Impact Factor -
Article: Does variation in workload affect fatigue in a regular 12‐hour shift system?
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ABSTRACT: The aim of the current study was to examine the relationship between workload and objective/subjective fatigue for a regularly rotating work schedule. Twenty male shift-workers working a 12-h schedule at a metallurgic smelter were involved in the study. Data were collected for a 14-day period while the participants continued their work schedule and duties. Shifts with high and low workload were separated and compared. Trends were observed for the increase of fatigue with a higher workload. Subjective fatigue was significantly higher at the end of the 12-h night shift (P < 0.05), and psychomotor vigilance test lapses occurred during the first half of the night shift (P < 0.05). These results imply that the relationships between workload, performance and subjective fatigue are complex and that further research is required.Sleep and Biological Rhythms 12/2006; 5(1):74 - 77. · 0.48 Impact Factor -
Article: Observations of age‐related differences in neurobehavioral performance in a 12‐hour shift system
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ABSTRACT: Research has indicated that individuals may become less tolerant to shiftwork as they age. This study observed the effect of age on neurobehavioral performance in shift workers working a 12-h shift schedule. Performance data was collected for a 14-day period, from 20 subjects. Analyses were performed to identify significant differences relating to age. Older subjects’ performance declined faster during night shifts than their younger counterparts, indicating a more profound effect of night work on performance in older workers. However, larger investigations are required to support generalized statements about the impact of age on performance.Sleep and Biological Rhythms 05/2006; 4(2):171 - 174. · 0.48 Impact Factor -
Article: Predicting the timing and duration of sleep in an operational setting using social factors.
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ABSTRACT: In recent years, there has been increasing interest in the use of bio-mathematical models to predict alertness, performance, and/or fatigue in operational settings. Current models use only biological factors to make their estimations, which can be limited in operational settings where social and geo-physical factors also dictate when sleep occurs. The interaction between social and biological factors that help determine the timing and duration of sleep during layover periods have been investigated in order to create and initially validate a mathematical model that may better predict sleep in the field. Participants were 32 male transmeridian airline pilots (17 captains, 10 first officers, and 5 second officers) flying the Sydney-Bangkok-London-Singapore-Sydney (SYD-LHR) pattern. Participants continued their regular schedule while wearing activity monitors and completing sleep and work diaries. The theoretical sleep timing model underpinning this analysis consists of separate formulations for short (<32 h) and long (>32 h) break periods. Longer break periods are split into three distinct phases-recovery (break start until first local night), personal (first local night until last local night), and preparation phases (last local night until break end)-in order to exploit potential differences specific to each. Furthermore, an iterative procedure combining prediction and retrodiction (i.e., using future duty timing information to predict current sleep timing) was developed to optimize predictive ability. Analysis found an interaction between the social and circadian sleep pressures that changed over the break period. Correlation analysis indicated a strong relationship between the actual sleep and new model's predictions (r = 0.7-0.9), a significant improvement when compared to existing models (r = 0.1-0.4). Social and circadian pressures play important roles in regulating sleep for international flight crews. An initial model has been developed in order to regulate sleep in these crews. The initial results have shown promise when applied to small sets of data; however, more rigorous validation must be carried out.Chronobiology International 01/2006; 23(6):1265-76. · 4.03 Impact Factor
Top co-authors
Top Journals
Institutions
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2006–2012
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University of South Australia
- Centre for Sleep Research
Adelaide, South Australia, Australia -
Walter Reed Army Institute of Research
Silver Spring, MD, USA
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2009–2011
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University of Adelaide
- Discipline of Medicine
Adelaide, South Australia, Australia
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2006–2011
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Repatriation General Hospital
Adelaide, South Australia, Australia
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