Stuart David Baulk
@online.unisa.edu.au
Online Course Facilitator, UniSA Online
University of South Australia
Scopus Publications
Scopus Publications
Andrew Vakulin, Peter G. Catcheside, Stuart D. Baulk, Nick A. Antic, Siobhan Banks, Jillian Dorrian, and R. Doug McEvoy
American Academy of Sleep Medicine (AASM)
STUDY OBJECTIVES
Obstructive sleep apnea (OSA) is associated with driving impairment and road crashes. However, daytime function varies widely between patients presenting a clinical challenge when assessing crash risk. This study aimed to determine the proportion of patients showing "normal" versus "abnormal" driving simulator performance and examine whether anthropometric, clinical, and neurobehavioral measures predict abnormal driving.
METHODS
Thirty-eight OSA patients performed a 90-min simulated driving task under 3 conditions: normal sleep, restricted sleep (4 h in bed), and normal sleep + alcohol (BAC∼0.05 g/dL). Patients were classified as "resilient" drivers if, under all 3 experimental conditions their mean steering deviation fell within 2 standard deviations of the mean steering deviation of 20 controls driving under baseline normal sleep conditions, or a "vulnerable" driver if mean steering deviation was outside this range in at least one experimental condition. Potentially predictive baseline anthropometric, clinical, neurocognitive, and cortical activation measures were examined.
RESULTS
Of the 38 OSA patients examined, 23 (61%) and 15 (39%) were classified as resilient and vulnerable drivers, respectively. There were no differences in baseline measures between the groups, although the proportion of females was greater and self-reported weekly driving exposure was less among vulnerable drivers (p < 0.05). On univariate analysis gender, weekly driving hours, and auditory event related potential P2 amplitude were weakly associated with group status. Multivariate analysis showed weekly driving hours (OR 0.69, 95%CI, 0.51-0.94, p = 0.02) and P2 amplitude (OR 1.34, 95%CI 1.02-1.76, p = 0.035) independently predicted vulnerable drivers.
CONCLUSIONS
Most OSA patients demonstrated normal simulated driving performance despite exposure to further sleep loss or alcohol. Most baseline measures did not differentiate between resilient and vulnerable drivers, although prior driving experience and cortical function were predictive. Novel measures to assist identification of OSA patients at risk of driving impairment and possibly accidents are needed.
TRIAL REGISTRATION
Data presented in this manuscript was collected as part of a clinical trial "Experimental Investigations of Driving Impairment in Obstructive Sleep Apnea." Trial ID: ACTRN12610000009011, URL: http://www.anzctr.org.au/trial_view.aspx?ID=334979.
Stuart D. Baulk and Adam Fletcher
Elsevier BV
Andrew Vakulin, Peter G. Catcheside, Stuart D. Baulk, Nick A. Antic, Cameron J. van den Heuvel, Siobhan Banks, and R. Doug McEvoy
Elsevier BV
Andrew VAKULIN, Peter G CATCHESIDE, Cameron J VAN DEN HEUVEL, Nick A ANTIC, R Doug MCEVOY, and Stuart D BAULK
Springer Science and Business Media LLC
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.
Andrew Vakulin, Stuart D. Baulk, Peter G. Catcheside, Nick A. Antic, Cameron J. van den Heuvel, Jillian Dorrian, and R. Doug McEvoy
American Academy of Sleep Medicine (AASM)
STUDY OBJECTIVES
To assess the effectiveness of CPAP treatment in improving 90-minute driving simulator performance in severe OSA patients compared to age/gender matched controls.
DESIGN
Driving simulator performance was assessed at baseline and 3 months later, with OSA patients treated with CPAP during the interval.
SETTING
University Teaching Hospital.
PARTICIPANTS
Patients with severe OSA (n = 11) and control subjects without OSA (n = 9).
INTERVENTIONS
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).
CONCLUSIONS
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.
TRIAL REGISTRATION
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=334979
Jillian Dorrian, Stuart D. Baulk, and Drew Dawson
Elsevier BV
Mark E. Howard, Melinda L. Jackson, and Stuart Baulk
Birkhäuser Basel
Andrew Vakulin, Stuart D. Baulk, Peter G. Catcheside, Nick A. Antic, Cameron J. van den Heuvel, Jillian Dorrian, and R. Doug McEvoy
American College of Physicians
Context Obstructive sleep apnea (OSA) is associated with sleepiness and poor concentration, symptoms that could impair driving performance. Contribution This study evaluated simulated driving performance in 38 patients with untreated OSA and 20 control participants under 3 conditions: unrestricted sleep, sleep restriction, and consumption of alcohol. Compared with control participants, patients with untreated OSA had worse simulated driving performance. Patients with OSA also had greater decrements in driving performance after sleep restriction and after alcohol consumption. Implication Consider alerting patients about the potential negative influence of untreated OSA on driving performance and their heightened vulnerability after sleep deprivation and alcohol consumption. The Editors Obstructive sleep apnea (OSA) causes excessive daytime somnolence and reduced vigilance, concentration, and neurocognitive function (1, 2). Patients with OSA, particularly those with moderate to severe disease, have a 2- to 7-fold increased risk for motor vehicle accidents (310). Community surveys have shown that approximately 7% of the middle-aged population has at least mild OSA (>10 obstructive events per hour of sleep) (1113), and up to 80% of these cases are undiagnosed (1416). For patients whose condition is diagnosed, delays in instituting treatment are common (17). Between 46% and 83% of patients do not adhere to treatment over the long term (18). The many patients with undiagnosed or untreated OSA represent a serious public health concern with respect to road safety. Accidents related to OSA result in an estimated 1400 road fatalities and cost $15.9 billion annually in the United States alone (19). Improving access to diagnosis and treatment may help reduce this public health burden. However, even with improved sleep medicine services, many unidentified or untreated patients with OSA will probably remain at increased risk for motor vehicle accidents. A better understanding of the factors contributing to motor vehicle accidents among patients with OSA is therefore needed to develop cost-effective prevention strategies. This study was designed to compare the effects of 2 common lifestyle factors, low-dose alcohol and acute partial sleep deprivation, on driving simulator performance between untreated patients with OSA and healthy matched control participants. We postulated that because of previous chronic sleep disruption and possible hypoxia-induced brain damage (2, 2026), patients with OSA would be more vulnerable to the effects of these common, mild central nervous system stressors and would experience significantly greater decrements in driving performance. Methods The study was approved by the Human Research Ethics Committees of the Repatriation General Hospital, University of South Australia, and University of Adelaide. Participants were introduced to the study objectives and protocol during an introductory session, gave written informed consent, and were remunerated for their participation. Study Design Patients with OSA and control participants underwent driving simulator assessments under 3 conditions that were presented in random and counterbalanced order: after a normal nighttime sleep, after a single night of sleep restriction (4 hours in bed from 2:00 a.m. to 6:00 a.m.), and after acute administration of low-dose alcohol (target blood alcohol concentration, 0.05 g/dL). All driving simulator sessions began at 2:00 p.m. and were conducted at least 5 days apart to avoid carryover effects from the previous interventions. Participant Selection Thirty-eight untreated patients with OSA of varying severity were recruited after diagnostic polysomnography. Neither they nor their referring physician had specific concerns about their driving. To minimize selection bias, patients were told that the study objective was to investigate general neurocognitive performance; they were unaware that the trial measured driving performance until after they agreed to attend an introductory session. Twenty healthy control participants matched for age and sex were recruited from the general population through newspaper advertisements, which only generally described the study and did not mention driving performance measures. Exclusion criteria were employment as a professional driver or shift worker; history of driving less than 2 years or less than 2 hours per week; notable medical comorbid conditions (such as cardiac or respiratory failure), periodic limb movement disorder (periodic limb movement arousal index >5 per hour), or past head injury or depression; use of alertness-altering prescription medications that may change neurocognitive function (such as antihistamines, opiates, or antidepressants); and history of alcohol abuse or current use of recreational drugs. Control participants were also excluded if they had higher-than-normal scores on sleep quality and daytime drowsiness questionnaires. Baseline Measures Before the driving simulator assessment, all participants completed questionnaires that evaluated general health (medical conditions, medication, alcohol intake, caffeine and drug use), sleep quality and habits, and daytime drowsiness using the Pittsburgh Sleep Quality Index (27) and the Epworth Sleepiness Scale (28). All participants underwent overnight standard diagnostic polysomnography with the following recordings: electroencephalography (C3/A2, C4/A1 lead placements), left and right electrooculography, submental electromyography, nasal cannulization to measure nasal pressure, limb movement sensors, inductive plethysmography for thoracoabdominal motion, lead II electrocardiography, and finger pulse oximetry (to measure arterial oxygen saturation). All signals were digitized and stored by using a Compumedics-E Series sleep system (Melbourne, Australia). Sleep and sleep arousals were scored by using standardized methods (29, 30). Apneas and hypopneas were scored according to internationally agreed-on criteria (30). All studies were scored by 1 staff member certified by the Board of Registered Polysomnographic Technicians. Table 1 shows participant characteristics, sleep study results, caffeine and alcohol consumption, and medication use. Table 1. Patient Characteristics, Polysomnography Results, and Medication Use Main Outcome Measures The main outcome measures were performance on the driving simulator, including lateral steering deviation, braking reaction time, crash frequency, and precrash electroencephalography and electrooculography results. Driving performance was assessed by using the AusEd driving simulator (Woolcock Institute for Medical Research, Sydney, Australia), which ran on a purpose-built Windows 2000 workstation (Microsoft, Redmond, Washington) with a 19-inch FP937s monitor (BenQ, Taipei, Taiwan); the MOMO steering wheel and pedals (Logitech, Fremont, California) were used to assess the driving variables. Steering deviation was measured as the average deviation in centimeters from the driver's median lane position sampled at 30 Hz. Participants were instructed to maintain speed within 60 to 80 km/h but to apply the brakes as quickly as possible whenever a slow-moving truck appeared ahead in the driving lane. The latter occurred 7 times during the drive, and the mean braking reaction time was computed for the 7 truck-ahead incidents. Crashes occurring throughout the driving task were defined as follows: car deviating from the road (all 4 wheels completely off the road), collision with a truck, or stationary position of the car for more than 3 seconds. The main outcome measure for crashes was the number of control participants and patients with OSA who experienced at least 1 crash incident. A secondary crash analysis was undertaken to determine whether crashes were associated with brief falling-asleep episodes and prolonged eye closures. Fifteen-second epochs of electroencephalography, electrooculography, and synchronized video (head and shoulders) before each crash (crash epoch) were scored for the presence of prolonged eye closure (>2 seconds) and microsleeps (>2 seconds of continuous electroencephalographic theta activity) within each crash epoch. A random sample of an equal number of 15-second noncrash epochs was selected and matched within participants and condition so that they could be compared with the crash epochs. The simulated driving task used in the study consisted of a 90-minute country nighttime drive on a predominantly straight dual-lane road with bends occurring at 10-minute intervals, each taking approximately 30 seconds to negotiate. There was no oncoming traffic or traffic lights. Driving simulator studies have been shown to correlate reasonably well with on-road driving (31, 32), and the AusEd simulator has been validated and shown to be sensitive to fatigue in a range of experimental settings (3337). Detailed Experimental Procedures For all 3 conditions, participants' sleep patterns and duration were monitored throughout the study by using actigraphy monitors (Actiwatch Model-AW64, Mini-Mitter Co., Bend, Oregon) worn from at least 5 days before the experiments began until study completion to estimate sleep/wake timing, to ensure adherence to the sleep restriction protocol, and to ensure that patients did not nap in the 24 hours before the experiments (38). In addition, during the night of sleep restriction, participants left a message on a time- and date-stamped answering machine at bedtime (2:00 a.m.) and wake time (6:00 a.m.), again to ensure adherence to the protocol. Participants were instructed to abstain from alcohol and caffeinated beverages, not to nap for 24 hours before each experimental session, and to consume breakfast before 9:00 a.m. on the day of each experiment. They were transported by taxi to and from the laboratory. Upon arrival at the laboratory at 12:00 p.m., each participant's blood alcohol concentration was estimated by using a calibrated breathalyzer (Alcotest7
Philippa GANDER, Dorothy BRUCK, Stuart BAULK, Roy BERAN, Rosemary HORNE, Mark HOWARD, and Naomi ROGERS
Springer Science and Business Media LLC
The Australasian Sleep Association (ASA) is seeking to develop a strategic research plan to improve the sleep health of Australians and New Zealanders, and to contribute to scientific understanding and clinical practice worldwide. To develop the plan, the ASA Research Committee undertook two projects: (i) a membership survey to establish the research activities, interests, and priorities of members; and (ii) compilation of an electronic library of citations of sleep-related research that involved one or more Australia-based or New Zealand-based researchers. Although the intent had been to develop an investigator-initiated research agenda for the ASA, these two projects revealed that such an approach would not provide a comprehensive and systematic research base to improve sleep health in Australasia. In particular, membership research interests were considered insufficient to adequately address public health issues relevant to the populations of Australia and New Zealand, clinical research for non-respiratory sleep disorders, and pediatric sleep research. The identification of these gaps raises a tension. If the ASA is to endorse additional research priority areas that are not major interests among its members, then additional research funding needs to be found, to avoid competing with the interests of members for limited existing research funding. To address this problem, a series of recommendations are offered to improve the proportion of existing health research funding that is directed towards sleep research, and to develop sources of new funding for sleep research.
S.D. Baulk, A. Fletcher, K.J. Kandelaars, D. Dawson, and G.D. Roach
Elsevier BV
S.D. Baulk, S.N. Biggs, K.J. Reid, C.J. van den Heuvel, and D. Dawson
Elsevier BV
Sarah N. Biggs, Andrew Smith, Jill Dorrian, Kathryn Reid, Drew Dawson, Cameron van den Heuvel, and Stuart Baulk
Elsevier BV
A. Vakulin, S.D. Baulk, P.G. Catcheside, R. Anderson, C.J. van den Heuvel, S. Banks, and R.D. McEvoy
Oxford University Press (OUP)
STUDY OBJECTIVE
To determine the combined effects of sleep restriction and low-dose alcohol on driving simulator performance, EEG, and subjective levels of sleepiness and performance in the mid-afternoon.
DESIGN
Repeated measures with 4 experimental conditions. Normal sleep without alcohol, sleep restriction alone (4 hours) and sleep restriction in combination with 2 different low blood alcohol concentrations (0.025 g/dL and 0.035 g/dL).
SETTING
Sleep Laboratory, Adelaide Institute for Sleep Health.
PARTICIPANTS
Twenty-one healthy young men, aged 18-30 years, mean (+/-SD) = 22.5(+/-3.7) years, BMI = 25(+/-6.7) kg/m2; all had normal sleep patterns and were free of sleep disorders.
MEASUREMENTS
Participants completed a 70-minute simulated driving session, commencing at 14:00. Driving parameters included steering deviation, braking reaction time, and number of collisions. Alpha and theta EEG activity and subjective driving performance and sleepiness were also measured throughout the driving task.
RESULTS
All measures were significantly affected by time. Steering deviation increased significantly when sleep restriction was combined with the higher dose alcohol. This combination also resulted in a significant increase in alpha/theta EEG activity throughout the drive, as well as greater subjective sleepiness and negative driving performance ratings compared to control or sleep restriction alone.
DISCUSSION
These data indicate that combining low-dose alcohol with moderate sleep restriction results in significant decrements to subjective alertness and performance as well as to some driving performance and EEG parameters. This highlights the potential risks of driving after consumption of low and legal doses of alcohol when also sleep restricted.
Stuart D BAULK, Katie J KANDELAARS, Nicole LAMOND, Gregory D ROACH, Drew DAWSON, and Adam FLETCHER
Springer Science and Business Media LLC
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.
Katie J. Kandelaars, Adam Fletcher, Jillian Dorrian, Stuart D. Baulk, and Drew Dawson
Informa UK Limited
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.
Katie J KANDELAARS, Stuart D BAULK, Adam FLETCHER, Guy EITZEN, Gregory D ROACH, and Drew DAWSON
Springer Science and Business Media LLC
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.
A. Fletcher, K. McCulloch, S.D. Baulk, and D. Dawson
Elsevier BV
Objective: Driver fatigue accounts for 10–40% of road crashes and is a critical area for public health. As other major road safety issues are more successfully managed, driver fatigue becomes proportionately more important. Both public awareness and legal developments have been slow to reach the same levels as for other road safety risks. The aim of this article is to review countermeasures for non‐commercial drivers that are designed to reduce the likelihood of fatigue‐related crashes through education and legislation.
James A. Horne and Stuart D. Baulk
Wiley
AbstractThe extent to which sleepy drivers are aware of sleepiness has implications for the prevention of sleep‐related crashes, especially for drivers younger than 30 years old who are most at risk. Using a real car interactive simulator, we report on EEG, subjective sleepiness, and lane drifting (sleepiness‐related driving impairment) from 38 sleep‐restricted, healthy young adults undergoing nontreatment control conditions from three (unpublished) investigations using the same experimental protocols for assessing various drinks intended to alleviate sleepiness. Participants drove 2 h during midafternoon under monotonous conditions. For all studies, subjective sleepiness and EEG activity indicative of sleepiness were highly correlated, with both changing concomitantly, along with lane drifting. Drivers had knowledge of their physiological sleepiness. There were indications that sugar content of these drinks may additionally affect sleepiness.
SD Baulk, LA Reyner, and JA Horne
Oxford University Press (OUP)
The application of reaction time (RT) as a secondary task to determine sleepiness in drivers is of increasing interest, but is a problematic area. We assessed the extent to which RT reflected this sleepiness, and/or otherwise affected driving behaviour in sleep restricted, moderately sleepy people. They drove a real-car interactive simulator for two, two hour afternoon monotonous drives, with and without RT (counterbalanced). Simple auditory RT was used, with a semi-random inter-stimulus interval averaging 21/2 minutes. Lane wandering (driving "incidents"), subjective and EEG measures of sleepiness were obtained. For both conditions all three indices changed significantly during the course of the afternoon circadian "dip". However, this was not reflected in RT, which remained relatively stable. Nevertheless, RT provided more "stimulation" for the sleepy driver, and significantly reduced subjective sleepiness, with a trend for fewer incidents and a more alert EEG. Possible reasons for the disparity in sensitivity between RT and the other measures are discussed. Under this experimental protocol, RT did not provide a useful guide to driver sleepiness; it was merely a mechanism for increasing task load and reducing monotony. The drivers' own insight into their sleepiness had more validity as a tool for assessing sleepiness.