Useful Field of View Impairments in Drivers with Obstructive Sleep Apnea

As a group, drivers with obstructive sleep apnea (OSA) have an increased risk for motor vehicle crashes, but determining individual crash risk is difficult. We tested the hypothesis that drivers with OSA have impaired visual attention, as indexed by reduced useful field of view (UFOV), a predictor of highrisk driving. Forty-one drivers with untreated OSA and 50 comparison drivers were assessed by UFOV. OSA drivers performed significantly worse than controls on all UFOV subtests and had reduced UFOV as indicated by a higher mean total UFOV score (p = 0.0017). However, only 4 OSA and 2 control drivers had values indicative of high crash risk (UFOV reduction \u3e23%). Drivers with OSA have reduced UFOV compared to drivers without neurological or sleep disorders. However, as UFOV identifies few high-risk drivers, its role in assessing crash risk in an unselected population of drivers with OSA appears to be limited

Variability of Driving Performance During Microsleeps

This study aimed to evaluate the value of measuring microsleeps as anindicator of driving performance impairment in drowsy drivers with sleepdisorders. Drivers with sleep disorders such as obstructive sleep apnea/hypopenasyndrome (OSAHS) are at increased risk for driving performance errors due tomicrosleep episodes, which presage sleep onset. To meet this aim, we tested thehypothesis that OSAHS drivers show impaired control over vehicle steering, laneposition and velocity during microsleep episodes compared to when they aredriving without microsleeps on similar road segments. A microsleep is defined asa 3-14 sec episode during which 4-7 Hz (theta) activity replaces the waking 8-13Hz (alpha) background rhythm. Microsleep episodes were identified in theelectroencephalography (EEG) record by a neurologist certified by the AmericanBoard of Sleep Medicine. Twenty-four drivers with OSAHS were tested usingsimulated driving scenarios. Steering variability, lane position variability,acceleration and velocity measures were assessed in the periods during amicrosleep, immediately preceding (pre) microsleep, and immediately following(post) microsleep. In line with our introductory hypothesis, drivers with OSAHSdid show significantly greater variation in steering and lane position during themicrosleep episodes compared to the periods pre and post microsleep. The resultsindicate that identification of microsleep episodes can provide a marker fordeclining vehicle control of drivers with OSAHS

Driving Performance and Driver State in Obstructive Sleep Apnea: What Changes with Positive Airway Pressure?

We evaluated naturalistic driving in 65 drivers with obstructive sleep apnea (OSA) before and after positive airway pressure (PAP) therapy and in 43 comparison drivers. Driving performance metrics included speed (mean, variability), and lateral, and longitudinal acceleration (g’s). Driver state measures included sleepiness and attention to the driving task based on sampled trigger and baseline video clips. OSA drivers showed less variability in speed and lateral g’s compared to control drivers before and after PAP treatment when vehicle speed wa

Effects of Fatigue on Real-World Driving in Diseased and Control Participants

This study evaluated real world driver errors and sleepiness in 66 drivers with Obstructive Sleep Apnea (OSA) and 34 matched controls (24 younger and 22 older). Driving errors and driver state were derived from analyses of video data from “black-box” event recorders. Sleep fragmentation data in OSA was derived from actigraphy for 15 days prior to beginning standard treatment (positive airway pressure, PAP) and 15 days after beginning PAP treatment. Prior to starting PAP, OSAs appeared sleepier than controls in general and particularly at intersections, while making safety errors following nights with high levels of fragmented sleep compared to matched controls. Adverse effects of sleep fragmentation during the pre-PAP phase were reduced post-PAP. Greater hours of PAP-use were associated with lower sleepiness and errors on the road. PAP-use was associated with a decrease in high sleep fragmented nights. Findings suggest reduction in acute sleepiness is unlikely to be the only mediating factor that explains the driving safety benefits of PAP in OSA

Effects of Environmental Factors on Naturalistic Driving in Obstructive Sleep Apnea

Reduced visibility and other environmental factors can impair driver ability to respond to roadway hazards. We examined the effects of reduced visibility on naturalistic driving in 66 drivers, including 45 at-risk drivers with obstructive sleep apnea (OSA) and 21 controls. We analyzed three months of electronic data using “black box” recorder technology and assessed the extent to which driver speed, longitudinal acceleration, and lateral acceleration metrics depend on ambient visibility from web-based environmental data archives. We calculated summary driving metrics within 10-second intervals, and reduced these to within-subject means and tested for associations of interest. OSA drivers did not differ from controls with respect to electronic measures or visibility conditions in which they drove. On average, drivers drove slower when visibility was reduced. After controlling for speed, variations in lateral and longitudinal acceleration were positively associated with high-visibility conditions. These findings suggest that drivers exert greater vehicular control when visibility is limited, and that this association is not just due to slower speeds. Weaker relationships between visibility and driving measures in OSA suggest reduced adaptive strategies. Our methods provide a framework for analyzing the effects of other environmental factors on driving, and we provide an additional example using wind speed

Steering Entropy Changes as a Function of Microsleeps

This study aimed to assess steering entropy as a measure of decrements in driving performance caused by microsleeps. Microsleeps are brief, unintended episodes of loss of attention that last 3-14 seconds. These episodes, which are frequent in drivers with sleep disorders, can be long enough to impact steering performance and are particularly disruptive when driver action is imperative, as when driving around curved highway segments. Steering entropy is a driver-centered performance measure that can detect drivers’ corrective responses to situations when the vehicle state falls outside the driver’s expectations. This study tests the hypothesis that steering entropy is an indicator of increased erratic steering behavior during microsleep episodes in drivers with obstructive sleep apnea/hypopena syndrome (OSAHS). Twenty-four drivers with OSAHS were used in this study and their electroencephalography (EEG) defined microsleep (cases) and non-microsleep episodes (crossover control) were compared using a case-crossover method. The performance measure, steering entropy, was calculated from a time-series history of steering angle data. Steering entropy was compared for each microsleep in the three-second interval both immediately preceding and immediately following each microsleep. Results showed that steering entropy was higher on curves during microsleeps and post microsleeps when compared to straight road segments and the no-workload baseline condition. This suggests that steering entropy can capture erratic steering behavior, allowing us to better understand how drivers correct for previous steering errors

Can Intermittent Video Sampling Capture Individual Differences in Naturalistic Driving?

We examined the utility and validity of intermittent video samples from black box devices for capturing individual difference variability in realworld driving performance in an ongoing study of obstructive sleep apnea (OSA) and community controls. Three types of video clips were coded for several dimensions of interest to driving research including safety, exposure, and driver state. The preliminary findings indicated that clip types successfully captured variability along targeted dimensions such as highway vs. city driving, driver state such as distraction and sleepiness, and safety. Sleepiness metrics were meaningfully associated with adherence to PAP (positive airway pressure) therapy. OSA patients who were PAP adherent showed less sleepiness and less non-driving related gaze movements than nonadherent patients. Simple differences in sleepiness did not readily translate to improvements in driver safety, consistent with epidemiologic evidence to date

Feedback from Naturalistic Driving Improves Treatment Compliance in Drivers with Obstructive Sleep Apnea

As part of a study in drivers with obstructive sleep apnea (OSA), we conducted a randomized clinical trial to assess whether individualized feedback can increase compliance with continuous positive airway pressure (CPAP) therapy. After completing 3.5 months of naturalistic driving monitoring, OSA drivers were randomized either to receive an intervention, which was feedback regarding their own naturalistic driving record and CPAP compliance, or to receive no such intervention. In the week immediately after the intervention date, drivers receiving feedback (n=30) improved their CPAP usage by an average of 35.8 minutes per night (p=0.008; 95% CI=9.6, 62.0) to a mean level of 296 minutes. By contrast, CPAP usage in the non-feedback group (n=36) decreased an average of 27.5 minutes per night (p=0.022; 95% CI=4.0, 51.0) to a mean level of 236 minutes. The mean group-specific changes were higher (better) in the feedback group than in the non-feedback group during the first, second, and third weeks of follow-up (p0.25 in all cases). Our study suggests that CPAP compliance can be increased using individualized feedback, but that follow-up feedback sessions or reminders may be necessary for sustained improvement

Linking GPS Data to GIS Databases in Naturalistic Studies: Examples from Drivers with Obstructive Sleep Apnea

In naturalistic studies, it is vital to give appropriate context when analyzing driving behaviors. Such contextualization can help address the hypotheses that explore a) how drivers perform within specific types of environment (e.g., road types, speed limits, etc.), and b) how often drivers are exposed to such specific environments. In order to perform this contextualization in an automated fashion, we are using Global Positioning System (GPS) data obtained at 1 Hz and merging this with Geographic Information Systems (GIS) databases maintained by the Iowa Department of Transportation (DOT). In this paper, we demonstrate our methods of doing this based on data from 43 drivers with obstructive sleep apnea (OSA). We also use maps from GIS software to illustrate how information can be displayed at the individual drive or day level, and we provide examples of some of the challenges that still need to be addressed

Using Feedback from Naturalistic Driving to Improve Treatment Adherence in Drivers with Obstructive Sleep Apnea

We are studying the effects of individualized feedback upon adherence with therapy (CPAP) in ongoing research aimed at improving driving safety in at-risk individuals with obstructive sleep apnea (OSA). The feedback includes specific samples of the individual’s own naturalistic driving record, both alert and drowsy, and record of CPAP adherence. We report on this methodology, provide data examples of CPAP usage, and show preliminary data on the results in the first eleven drivers who received this intervention