The impact of alcohol consumption on commercial eye blink drowsiness detection technology.

INTRODUCTION: Driver drowsiness detection technology that assesses eye blinks is increasingly being used as a safety intervention in the transport industry. It is unclear how alcohol consumption to common legal driving limits impacts upon this technology. The aim of the study was to assess the impact of a blood alcohol content (BAC) of 0.05% and of 0.08% on drowsiness detection technology during simulated driving. METHODS: Participants completed a 60-min driving simulation and sleepiness questionnaire under three conditions: 1-0.00% BAC, 2-0.05% BAC and 3-0.08% BAC. During the driving simulation task participants wore a commercial eye blink drowsiness detection technology (Optalert) with the drowsiness alarms silenced. RESULTS: Twelve participants (3 female) completed all alcohol conditions. Relative to baseline, all eye blink parameters were affected at 0.08% BAC (all p < 0.05), whereas 0.05% BAC only affected the composite eye blink drowsiness measure (the Johns Drowsiness Scale). CONCLUSIONS: Alcohol consumption to 0.08% BAC impaired eye blink measures to a level that would be considered a moderate drowsiness risk. Therefore, employers should be aware that drowsiness alerts from these technologies may increase after alcohol consumption.

A brief assessment of eye blink drowsiness immediately prior to or following driving detects drowsiness related driving impairment.

Drowsy driving is a major cause of fatal and serious injury motor vehicle accidents. The inability objectively to assess drowsiness has hindered the assessment of fitness to drive and the development of drowsy driving regulations. This study evaluated whether spontaneous eye blink parameters measured briefly pre- and post-drive could be used to detect drowsy driving impairment. Twelve healthy participants (6 female) drove an instrumented vehicle for 2 h on a closed-loop track during a rested (8-10 h awake) and an extended wake condition (32-34 h awake). Pre- and post-drive, the participants completed a 5 min eye blink task, a psychomotor vigilance task (PVT), and the Karolinska sleepiness scale (KSS). Whole drive impairment was defined as >3.5 lane departures per hour. Severe end of drive impairment was defined as ≥2 lane departures in the last 15 min. The pre-drive % of time with eyes closed best predicted the whole drive impairment (area under the curve [AUC] 0.87). KSS had similar prediction ability (AUC 0.85), while PVT reaction time (AUC 0.72) was less accurate. The composite eye blink parameter, the Johns drowsiness scale was the best retrospective detector of severe end of drive impairment (AUC 0.99). The PVT reaction time (AUC 0.92) and the KSS (AUC 0.93) were less accurate. Eye blink parameters detected drowsy driving impairment with an accuracy that was similar to, or marginally better than, PVT and KSS. As eye blink measures are simple to measure, are objective and have high accuracy, they present an ideal option for the assessment of fitness for duty and roadside drowsiness.

Eye blink parameters to indicate drowsiness during naturalistic driving in participants with obstructive sleep apnea: A pilot study.

OBJECTIVES: To determine whether continuous eye blink measures could identify drowsiness in patients with obstructive sleep apnea (OSA) during a week of naturalistic driving. DESIGN: Observational study comparing OSA patients and healthy controls. SETTING: Regular naturalistic driving across one week. PARTICIPANTS: Fifteen untreated moderate to severe OSA patients and 15 age (± 5 years) and sex (female = 6) matched healthy controls. MEASUREMENTS: Participants wore an eye blink drowsiness recording device during their regular driving for one week. RESULTS: During regular driving, the duration of time with no ocular movements (quiescence), was elevated in the OSA group by 43% relative to the control group (mean [95% CI] 0.20[0.17, 0.25] vs 0.14[0.12, 0.18] secs, P = .011). During long drives only, the Johns Drowsiness Scale was also elevated and increased by 62% in the OSA group relative to the control group (1.05 [0.76, 1.33] vs 0.65 [0.36, 0.93], P = .0495). Across all drives, critical drowsiness events (defined by a Johns Drowsiness Scale score ≥2.6) were twice as frequent in the OSA group than the control group (rate ratio [95% CI] =1.93 [1.65, 2.25], P ≤ .001). CONCLUSIONS: OSA patients were drowsier than healthy controls according to some of the continuous real time eye blink drowsiness measures. The findings of this pilot study suggest that there is potential for eye blink measures to be utilized to assess fitness to drive in OSA patients. Future work should assess larger samples, as well as the relationship of eye blink measures to conventional fitness to drive assessments and crash risk.

The impact of heart rate-based drowsiness monitoring on adverse driving events in heavy vehicle drivers under naturalistic conditions.

OBJECTIVES: This study examined the influence of a wrist-worn heart rate drowsiness detection device on heavy vehicle driver safety and sleep and its ability to predict driving events under naturalistic conditions. DESIGN: Prospective, non-randomized trial. SETTING: Naturalistic driving in Malaysia. PARTICIPANTS: Heavy vehicle drivers in Malaysia were assigned to the Device (n = 25) or Control condition (n = 34). INTERVENTION: Both conditions were monitored for driving events at work over 4-weeks in Phase 1, and 12-weeks in Phase 2. In Phase 1, the Device condition wore the device operated in the silent mode (i.e., no drowsiness alerts) to examine the accuracy of the device in predicting driving events. In Phase 2, the Device condition wore the device in the active mode to examine if drowsiness alerts from the device influenced the rate of driving events (compared to Phase 1). MEASUREMENTS: All participants were monitored for harsh braking and harsh acceleration driving events and self-reported sleep duration and sleepiness daily. RESULTS: There was a significant decrease in the rate of harsh braking events (Rate ratio = 0.48, p < 0.05) and a fall in subjective sleepiness (p < 0.05) when the device was operated in the active mode (compared to the silent mode). The device predicted when no driving events were occurring (specificity=98.81%), but had low accuracy in detecting when a driving event did occur (sensitivity=6.25%). CONCLUSIONS: Including drowsiness detection devices in fatigue management programs appears to alter driver behaviour, improving safety despite the modest accuracy. Longer term studies are required to determine if this change is sustained.

Assessing the validity of eyelid parameters to detect impairment due to benzodiazepines.

OBJECTIVE: Benzodiazepines impair driving ability and psychomotor function. Eyelid parameters accurately reflect drowsiness; however, the effects of benzodiazepines on these measures have not been extensively studied. The aim of this study was to investigate the effect of benzodiazepines on eyelid parameters and evaluate their accuracy for detecting psychomotor impairment. METHODS: Eyelid parameters were recorded during a psychomotor vigilance task (PVT) and driving simulation over 2 days, baseline, and after 20-mg oral temazepam. The utility of eyelid parameters for detecting PVT lapses was evaluated using receiver operating characteristic curves, and cut-off levels indicating impairment (≥1 and ≥2 PVT lapses per min) were identified. The accuracy of these cut-off levels for detecting driving simulator crashes was then examined. RESULTS: PVT and driving simulator performance was significantly impaired following benzodiazepine administration (p < .05). Average eyelid closure duration (inter-event duration) was a reliable indicator of PVT lapses (area under the curve [AUC] of 0.87-0.90). The cut-off value of eyelid closure duration derived from PVT AUC was able to predict driving simulator crashes with moderately high sensitivity and specificity (76.23% and 75.00%). CONCLUSIONS: Eyelid parameters were affected by benzodiazepines and accurately detected the psychomotor impairment. In particular, eyelid closure duration is a promising real-time indicator of benzodiazepine impairment.

Eye-Blink Parameters Detect On-Road Track-Driving Impairment Following Severe Sleep Deprivation.

STUDY OBJECTIVES: Drowsiness leads to 20% of fatal road crashes, while inability to assess drowsiness has hampered drowsiness interventions. This study examined the accuracy of eye-blink parameters for detecting drowsiness related driving impairment in real time. METHODS: Twelve participants undertook two sessions of 2-hour track-driving in an instrumented vehicle following a normal night's sleep or 32 to 34 hours of extended wake in a randomized crossover design. Eye-blink parameters and lane excursion events were monitored continuously. RESULTS: Sleep deprivation increased the rates of out-of-lane driving events and early drive terminations. Episodes of prolonged eyelid closures, blink duration, the ratio of amplitude to velocity of eyelid closure, and John's Drowsiness Score (JDS, a composite score) were also increased following sleep deprivation. A time-on-task (drive duration) effect was evident for out-of-lane events rate and most eye-blink parameters after sleep deprivation. The JDS demonstrated the strongest association with the odds of out-of-lane events in the same minute, whereas measures of blink duration and prolonged eye closure were stronger indicators of risk for out-of-lane events over longer periods of 5 minutes and 15 minutes, respectively. Eye-blink parameters also achieved moderate accuracies (specificities from 70.12% to 84.15% at a sensitivity of 50%) for detecting out-of-lane events in the same minute, with stronger associations over longer timeframes of 5 minutes to 15 minutes. CONCLUSIONS: Eyelid closure parameters are useful tools for monitoring and predicting drowsiness-related driving impairment (out-of-lane events) that could be utilized for monitoring drowsiness and assessing the efficacy of drowsiness interventions. CLINICAL TRIAL REGISTRATION: This study is registered with the Australian New Zealand Clinical Trial Registry (ANCTR), http://www.anzctr.org.au/TrialSearch.aspx ACTRN12612000102875. CITATION: Shekari Soleimanloo S, Wilkinson VE, Cori JM,Westlake J, Stevens B, Downey LA, Shiferaw BA, Rajaratnam SMW, Howard ME. Eye-blink parameters detect on-road track-driving impairment following severe sleep deprivation. J Clin Sleep Med. 2019;15(9):1271-1284.

Profile of an HIV Testing and Counseling Unit in Bangladesh: Majority of New Diagnoses among Returning Migrant Workers and Spouses.

INTRODUCTION: Analysis of data from HIV testing and counseling (HTC) services provides an opportunity to identify important populations for targeting of HIV prevention efforts. Our primary aim was to describe the demographics of clients presenting to HTC in Bangladesh, a low HIV prevalence country. Our secondary aim was to determine the risk factors for HIV positivity among returning migrant workers who were tested. METHODS: We performed a cross-sectional study of data collected between 2002 and 2010 from the first HTC service established in Bangladesh, located in three large cities. RESULTS: 8973 individuals attended HTC services, with 558 (6.2%) of clients testing positive for HIV, including 33 children. The majority of those who tested positive were aged 25-44 (71%), male (70%), and married (68%). Key populations considered at increased risk of HIV, such as female sex workers, people who inject drugs, and males who have sex with males accounted for only 11% of adults who tested positive. Notably, 75% of adults testing positive had a history of migrant work or was the spouse of a migrant worker. In multivariable logistic regression of those with a migrant work history presenting for HTC, we found rural residence, working in the Middle East, and longer duration of migrant work to be independently associated with testing positive, and female gender and higher level of education to be negatively associated. CONCLUSIONS: These data suggest that in Bangladesh, in addition to targeting traditional key populations, HIV prevention efforts should also focus on migrant workers and their spouses.

Specific sleepiness symptoms are indicators of performance impairment during sleep deprivation.

Drivers are not always aware that they are becoming impaired as a result of sleepiness. Using specific symptoms of sleepiness might assist with recognition of drowsiness related impairment and help drivers judge whether they are safe to drive a vehicle, however this has not been evaluated. In this study, 20 healthy volunteer professional drivers completed two randomized sessions in the laboratory - one under 24h of acute sleep deprivation, and one with alcohol. The Psychomotor Vigilance Task (PVT) and a 30min simulated driving task (AusEdTM) were performed every 3-4h in the sleep deprivation session, and at a BAC of 0.00% and 0.05% in the alcohol session, while electroencephalography (EEG) and eye movements were recorded. After each test session, drivers completed the Karolinska Sleepiness Scale (KSS) and the Sleepiness Symptoms Questionnaire (SSQ), which includes eight specific sleepiness and driving performance symptoms. A second baseline session was completed on a separate day by the professional drivers and in an additional 20 non-professional drivers for test-retest reliability. There was moderate test-retest agreement on the SSQ (r=0.59). Significant correlations were identified between individual sleepiness symptoms and the KSS score (r values 0.50-0.74, p<0.01 for all symptoms). The frequency of all SSQ items increased during sleep deprivation (χ(2) values of 28.4-80.2, p<0.01 for all symptoms) and symptoms were related to increased subjective sleepiness and performance deterioration. The symptoms "struggling to keep your eyes open", "difficulty maintaining correct speed", "reactions were slow" and "head dropping down" were most closely related to increased alpha and theta activity on EEG (r values 0.49-0.59, p<0.001) and "nodding off to sleep" and "struggling to keep your eyes open" were related to slow eye movements (r values 0.67 and 0.64, p<0.001). Symptoms related to visual disturbance and impaired driving performance were most accurate at detecting severely impaired driving performance (AUC on ROC curve of 0.86-0.91 for detecting change in lateral lane position greater than the change at a BAC of 0.05%). Individual sleepiness symptoms are related to impairment during acute sleep deprivation and might be able to assist drivers in recognizing their own sleepiness and ability to drive safely.

The accuracy of eyelid movement parameters for drowsiness detection.

STUDY OBJECTIVES: Drowsiness is a major risk factor for motor vehicle and occupational accidents. Real-time objective indicators of drowsiness could potentially identify drowsy individuals with the goal of intervening before an accident occurs. Several ocular measures are promising objective indicators of drowsiness; however, there is a lack of studies evaluating their accuracy for detecting behavioral impairment due to drowsiness in real time. METHODS: In this study, eye movement parameters were measured during vigilance tasks following restricted sleep and in a rested state (n = 33 participants) at three testing points (n = 71 data points) to compare ocular measures to a gold standard measure of drowsiness (OSLER). The utility of these parameters for detecting drowsiness-related errors was evaluated using receiver operating characteristic curves (ROC) (adjusted by clustering for participant) and identification of optimal cutoff levels for identifying frequent drowsiness-related errors (4 missed signals in a minute using OSLER). Their accuracy was tested for detecting increasing frequencies of behavioral lapses on a different task (psychomotor vigilance task [PVT]). RESULTS: Ocular variables which measured the average duration of eyelid closure (inter-event duration [IED]) and the ratio of the amplitude to velocity of eyelid closure were reliable indicators of frequent errors (area under the curve for ROC of 0.73 to 0.83, p < 0.05). IED produced a sensitivity and specificity of 71% and 88% for detecting ≥ 3 lapses (PVT) in a minute and 100% and 86% for ≥ 5 lapses. A composite measure of several eye movement characteristics (Johns Drowsiness Scale) provided sensitivities of 77% and 100% for detecting 3 and ≥ 5 lapses in a minute, with specificities of 85% and 83%, respectively. CONCLUSIONS: Ocular measures, particularly those measuring the average duration of episodes of eye closure are promising real-time indicators of drowsiness.

Discharge patterns of human genioglossus motor units during arousal from sleep.

STUDY OBJECTIVES: Single motor unit recordings of the human genioglossus muscle reveal motor units with a variety of discharge patterns. Integrated multiunit electromyographic recordings of genioglossus have demonstrated an abrupt increase in the muscle's activity at arousal from sleep. The aim of the present study was to determine the effect of arousal from sleep on the activity of individual motor units as a function of their particular discharge pattern. DESIGN: Genioglossus activity was measured using intramuscular fine-wire electrodes inserted via a percutaneous approach. Arousals from sleep were identified using the ASDA criterion and the genioglossus electromyogram recordings analyzed for single motor unit activity. SETTING: Sleep research laboratory. PARTICIPANTS: Sleep and respiratory data were collected in 8 healthy subjects (6 men). MEASUREMENTS AND RESULTS: 138 motor units were identified during prearousalarousal sleep: 25% inspiratory phasic, 33% inspiratory tonic, 4% expiratory phasic, 3% expiratory tonic, and 35% tonic. At arousal from sleep inspiratory phasic units significantly increased the proportion of a breath over which they were active, but did not appreciably increase their rate of firing. 80 new units were identified at arousals, 75% were inspiratory, many of which were active for only 1 or 2 breaths. 22% of units active before arousal, particularly expiratory and tonic units, stopped at the arousal. CONCLUSIONS: Increased genioglossus muscle activity at arousal from sleep is primarily due to recruitment of inspiratory phasic motor units. Further, activity within the genioglossus motoneuron pool is reorganized at arousal as, in addition to recruitment, approximately 20% of units active before arousals stopped firing.

Discharge patterns of human genioglossus motor units during sleep onset.

STUDY OBJECTIVES: Multiunit electromyogram recordings of genioglossus have demonstrated an abrupt reduction in the muscle's activity at sleep onset. Recent evidence from single motor unit recordings indicates that the human genioglossus muscle consists of motor units with a variety of discharge patterns. The aim of the present study was to determine the effect of sleep onset on the activity of individual motor units as a function of their particular discharge pattern. DESIGN: Genioglossus activity was assessed using intramuscular fine-wire electrodes via a percutaneous approach. Sleep onsets (alpha-to-theta transitions) were identified and the genioglossus electromyogram recordings analyzed for single motor unit activity. SETTING: Sleep research laboratory. PARTICIPANTS: Sleep and respiratory data were collected in 8 healthy subjects (6 men). MEASUREMENTS AND RESULTS: One hundred twenty-seven motor units were identified: 23% inspiratory phasic, 45% inspiratory tonic, 4% expiratory phasic, 9% expiratory tonic, 16% tonic, and 3% other. Approximately 50% of inspiratory units (phasic and tonic) ceased activity entirely at sleep onset, whereas those inspiratory units that continued to be active showed a reduction in the proportion of each breath over which they were active. However, the rate of discharge of inspiratory units during the period they did fire was not altered. In contrast, tonic and expiratory units were unaffected by sleep onset, maintaining their discharge pattern over the alpha-to-theta transition. CONCLUSIONS: Central control of inspiratory motoneuron output differs from that of tonic and expiratory units during sleep onset, suggesting that the maintenance of airway patency during sleep may become more reliant on the stiffening properties of tonic and expiratory modulated motor units.