Evaluation of driver drowsiness based on respiratory metrics

BACKGROUND

The transition from alertness to drowsiness can cause considerable changes in the respiratory system, providing an opportunity to detect driver drowsiness.

OBJECTIVE

The aim of this study was to determine which respiratory features indicate driver drowsiness and then use these features to classify the level of drowsiness and alertness.

METHODS

Twenty male students (mean age 25.6±2.41 years) participated in the study using a driving simulator, and eight features, including expiration duration (ED), inspiration duration (ID), peak-to-peak amplitude (PA), inspiration-to-expiration time ratio (I/E ratio), driving, timing, respiration rate (RR), and yawning, were extracted from the respiratory signal generated by abdominal motions using a belt equipped with a force sensor.

RESULTS

All eight features were statistically significant at the significance level of 0.05. Drowsiness can be detected using respiratory features with 88% accuracy, 82% precision, 86% recall, and an 90% F1 score.

CONCLUSION

The findings of this study may be useful in the development of driver drowsiness monitoring systems based on less intrusive respiratory signal analysis, particularly for specific process automation applications when vehicle control is not in the hands of the driver.

Hydrogen-rich water and caffeine for alertness and brain metabolism in sleep-deprived habitual coffee drinkers

The main aim of this randomized-controlled cross-over interventional trial was to assess the acute effects of taking a single dose of hydrogen-rich water (HRW), and compare it with caffeine, HRW plus caffeine, and control water, for alertness, brain metabolism, brain and oxygen saturation, and self-reported adverse events in healthy men and women who were habitual coffee drinkers and were sleep-deprived for 24 hr. Sixteen apparently healthy young adults (8 men and 8 women; age 24.0 ± 3.5 years) were allocated in a cross-over design to receive a single-dose drink of HRW (8 ppm), caffeine (50 mg), HRW plus caffeine, or control drink (tap water) in the morning after 24-hr sleep deprivation and 12-hr fasting. The primary and secondary outcomes were assessed at baseline (pre-intervention) and 15-min follow-up. Significantly less time was needed to complete trail-making test after both HRW and HRW plus caffeine compared with the control drink (p < .05). The number of errors in the symbol digit modalities test was significantly lower after drinking HRW or caffeine than control drink (p < .05). Both HRW and caffeine significantly increased the choline-to-creatine ratio in several brain regions (frontal white and gray matter), while HRW and the combination intervention also affected brain metabolism in the paracentral brain. No participants reported any side effects from any intervention. The attention enhancement driven by HRW appears along with changes in brain metabolism. Being generally recognized as a safe intervention, hydrogen could be thus recommended as a novel intervention that upholds attention in stressed conditions, with its metabolic footprint likely different from caffeine.

The effects of caffeine on drowsiness in patients with narcolepsy: a double-blind randomized controlled pilot study

PURPOSE

The effects of caffeine on drowsiness and reaction time in patients with narcolepsy are unclear. We aimed to assess the effects of caffeine as add-on therapy in narcolepsy patients.

METHODS

A randomized, double-blind, placebo-control clinical pilot trial was conducted with a parallel, two-arm trial allocation ratio of 1:1. Participants attended two study visits 7 days apart. The drug was administered orally in a single opaque capsule containing 200 mg caffeine/placebo daily in the morning for 1 week. Sleepiness was assessed objectively using infrared reflectance oculography to measure the percentage of long eye closure (LEC%) and subjectively using two sleepiness scales, the Stanford Sleepiness Scale (SSS) and Karolinska Sleepiness Scale (KSS). Parameters were measured at baseline (BL) prior to taking the drug, after taking the first dose (FD), and after 1 week (WD) of daily caffeine.

RESULTS

Sixteen participants with narcolepsy were included. No significant differences between groups in baseline measurements were observed. LEC% was significantly decreased after the FD and WD compared with baseline levels (BL 1.4 ± 2.1 vs. FD 0.06 ± 0.0.6 and WD 0.03 ± 0.04). Significant improvements in alertness were observed using the KSS when comparing BL with FD and WD (6.3 ± 1.6, 4.9 ± 1.7, and 4.7 ± 1.7, respectively; p = 0.01). No changes in reaction time or SSS scores were noted.

CONCLUSION

Our findings suggest that a small dose of caffeine has positive effects on alertness in patients with narcolepsy. However, larger trials are required to confirm these findings.

TRIAL REGISTRATION NO

ClinicalTrial.gov NCT02832336.

Effects of caffeine on sleep quality and daytime functioning

Caffeine (particularly in the form of coffee) is one of the most widely consumed stimulants in the world, with 90% of American adults consuming caffeine-infused beverages almost daily. While there is substantial evidence that caffeine enhances performance, caffeine withdrawal leads to deficits at both the individual (eg, cognitive, emotional, and behavioral processes) and societal (eg, increases in work accidents) level. Scholars for some time have considered that the supposed psychoactive benefits of caffeine may be the result of the mere reversal of deleterious effects of caffeine withdrawal, rather than a net benefit of caffeine ingestion. In this integrative review, we examine evidence illuminating the relationship between caffeine consumption and subsequent quality and quantity of nighttime rest. Secondly, we consider evidence as to whether performance deficits caused by sleep deprivation linked to caffeine can be reversed by caffeine consumption during the subsequent daytime period. Finally, we consider how these two stages can be reconciled in a single model that enables calculation of the net caffeine effect on daytime functioning. The literature highlights a range of positive impacts of caffeine consumption on both physical and cognitive functioning. There are also a number of factors that complicate any conclusions that can be drawn regarding the potential of caffeine to improve performance. Most critically, performance improvements the next day may simply be a result of the reversal of caffeine withdrawal. Animal studies and well-controlled human studies involving high habitual and low habitual users tend to confirm a "net benefit" for caffeine use. Further research, particularly with (necessarily rare) caffeine-naive populations, is required to elucidate the complexities of the relationship between caffeine, sleep, and daytime functioning. However, the convenience of accessing caffeine compared to ensuring adequate restorative sleep means that caffeine has applied advantages that are likely to see its use as a performance "enhancing" substance persist.

Effects of acute and chronic caffeine on risk-taking behavior in children and adolescents

Consumption of caffeinated beverages is associated with increased risk-taking behavior. The purpose of this study was to determine if acute caffeine administration influences risk-taking behavior in a dose-dependent manner. Participants were pre- (ages 8-9) and post-pubertal (ages 15-17) children who visited the laboratory three times and consumed a beverage containing 0, 1, or 2 mg/kg of caffeine. Thirty minutes later, participants completed the balloon analogue risk task (BART), the Iowa gambling task (IGT), and a delay discounting task. The number of balloons exploded on the BART task was significantly increased after 2 mg/kg of caffeine in moderate caffeine consumers, but was decreased after 2 mg/kg of caffeine in high caffeine consumers. There were no main effects of caffeine dose on the delay discounting task or on the IGT. Post-pubertal participants showed reduced delay discounting compared with pre-pubertal participants. Finally, average daily caffeine use was significantly, positively correlated with scores on a risk-taking questionnaire. These data suggest that caffeine dose-dependently influences decision making and risk taking. More research is needed to determine the mechanism of this difference as well as the extent to which sex and pubertal phase influence these relationships.

The Effects of Caffeine Use on Driving Safety Among Truck Drivers Who Are Habitual Caffeine Users

The purpose of this study was to describe caffeine use among a group of habitual caffeine users, truck drivers, and to explore the associations between caffeine use and critical safety events by age in the naturalistic work setting. A secondary analysis of existing data from the Naturalistic Truck Driving Study was conducted. Analyses focused on the association between sleep and caffeine consumption by duty status, comparisons of sleep and caffeine use by age, and the associations between caffeine use and safety-critical events (SCEs). Findings indicated differences in caffeine use by duty status. However, no difference in sleep time by duty status, or between sleep time and caffeine use was found regardless of when the caffeine was consumed during the 5 hours prior to sleep. Sleep time did not vary significantly by age, although increasing age was associated with decreased caffeine use. Overall, a 6% reduction in the rate of SCEs per eight ounces of caffeinated beverage consumed was found. This study makes a unique scientific contribution because it uses real-time observations of truckers in the naturalistic work setting. It also does not involve caffeine withdrawal but rather an investigation of the effects of the naturalistic consumption of caffeine on sleep and driving performance. Findings suggest that caffeine use among habitual users offers a protective effect for safety-critical driving events. Occupational health nurses may use this information to counsel workers in the use of caffeine to enhance driving safety.

The effect of caffeine on working memory load-related brain activation in middle-aged males

Caffeine is commonly consumed in an effort to enhance cognitive performance. However, little is known about the usefulness of caffeine with regard to memory enhancement, with previous studies showing inconsistent effects on memory performance. We aimed to determine the effect of caffeine on working memory (WM) load-related activation during encoding, maintenance and retrieval phases of a WM maintenance task using functional magnetic resonance imaging (fMRI). 20 healthy, male, habitual caffeine consumers aged 40-61 years were administered 100 mg of caffeine in a double-blind placebo-controlled crossover design. Participants were scanned in a non-withdrawn state following a workday during which caffeinated products were consumed according to individual normal use (range = 145-595 mg). Acute caffeine administration was associated with increased load-related activation compared to placebo in the left and right dorsolateral prefrontal cortex during WM encoding, but decreased load-related activation in the left thalamus during WM maintenance. These findings are indicative of an effect of caffeine on the fronto-parietal network involved in the top-down cognitive control of WM processes during encoding and an effect on the prefrontal cortico-thalamic loop involved in the interaction between arousal and the top-down control of attention during maintenance. Therefore, the effects of caffeine on WM may be attributed to both a direct effect of caffeine on WM processes, as well as an indirect effect on WM via arousal modulation. Behavioural and fMRI results were more consistent with a detrimental effect of caffeine on WM at higher levels of WM load, than caffeine-related WM enhancement. This article is part of a Special Issue entitled 'Cognitive Enhancers'.