Keeping on the Straight and Narrow

The issue of drowsy driving has been on the public safety agenda for many years and yet little headway has been made in combating the issue. Shift workers are acknowledged to be at high risk of drowsing driving accidents, with at least twice the odds of falling asleep while driving.¹ Furthermore, the number of night shifts in a month positively predicts motor vehicle accidents and near-crashes.² Thus countermeasure development and testing remain critical. The most obvious approach to reduce the incidence of drowsy driving after night shifts is to provide alternative transportation, such as convenient public transportation or employer paid vouchers for private transportation (e.g., taxis). Unfortunately, these options are not always available.

Another approach is to reduce the circadian misalignment that contributes to the increased sleepiness during the night shift and commute home and disrupted sleep during the daytime. Most circadian interventions for night work are focused on promoting a circadian phase delay and include reducing exposure to morning light (dark sunglasses during commute home, early to bed after night shift in a dark bedroom) and increasing bright light exposure during the night shift (until ∼4 am).^3,4 To avoid circadian misalignment on days off, workers need to sleep late on their days off,^3,4 which is not always possible, especially for those with family responsibilities. Nonetheless, some night workers are able to achieve circadian adaptation naturally.^5,6 Indeed, circadian interventions for night workers in the field have been fairly successful (nurses,⁷ police officers⁸). However, there is concern that dark sunglasses during the commute home will reduce the acute alerting effects of morning light, which may increase the already heightened risk for vehicular accidents.⁹ A further approach to reduce drowsy driving after the night shift is to target the heightened sleep pressure by napping either before or (if permitted) in the workplace, during the night shift. Indeed, a 40-minute nap at 3 am during the night shift in emergency department medical workers reduced off-road deviations and collisions with oncoming vehicles during a simulated driving test during the usual commute home time.¹⁰ However, as with any planned nap strategy, sleep inertia following naps needs to be taken into consideration.¹¹

Wake promoting agents represent an additional tool that may be useful in reducing the risk of driving home drowsy after the night shift. Several wake promoting agents have been tested in the shift work environment including caffeine, modafinil, and armodafinil.¹² Wake promoting agents tested to improve simulated driving performance following sleep deprivation include caffeine, caffeine combined with a nap, caffeine-containing energy drinks, and modafinil.^13–16 In this issue of SLEEP, Drake and colleagues¹⁷ take a significant step forward, by reporting on the first investigation of a wake promoting agent on driving performance in shift workers. They studied 20 night workers in a randomized, double-blind, crossover design, with a 1-2 week washout between conditions. The night workers met criteria for shift work disorder (ICSD-2) and thus represented the 10% to 30% of night workers with the most significant complaints.¹⁸ The night workers were screened by questionnaire for sleep apnea risk, but their BMI was not reported. The night workers worked at least 3 consecutive night shifts prior to each laboratory session and received either 150 mg armodafinil or placebo at 23:45, which was ∼3.25 h after their usual shift start time (Table 1).¹⁷ Outcome measures assessed until 9:30 in the morning included a 30-minute simulated driving task with measures of weaving (standard deviation of lateral position) and off-road deviations, an objective measure of sleepiness (multiple sleep latency test [MSLT]), a subjective measure of sleepiness (Karolinska Sleepiness Scale), and two other measures of cognitive performance. The major finding was that compared to placebo, armodafinil significantly reduced weaving and off-road deviations during the 7:00 and 9:00 driving tasks, which is the time of the usual commute home. Based on the pharmacokinetics of armodafinil, one can estimate that ∼75% of the drug would still be in the circulation at this time, or even more following food intake.¹⁹ Notably, however, even after taking armodafinil, workers were still excessively sleepy at 7:00-7:30, as indicated by an average sleep latency of about 7 minutes²⁰ and an average of more than 5 off-road events.

Strengths of this research include the study of real night workers with shift work sleep disorder and the use of a driving task, albeit simulated. This work is one step closer to assessing actual driving performance and very importantly, the assessment of simulated driving occurred at the night workers' usual time of driving home. Thus, the ecological validity of the assessment is much higher than the usual measures of alertness and performance included in night shift studies and focuses on a time that is often overlooked but poses a significant risk. Nonetheless, while wake promoting agents are an important tool, they do not restore alertness to the levels observed in well-rested day workers.²¹ Additionally, alternative nonpharmacological interventions are needed for those individuals who experience side effects,¹² are taking interacting medications (e.g., steroidal contraceptives, clopidogrel),²² or are unwilling to take additional prescription medications.

Future research should measure actual driving performance, which is possible in specially equipped cars.^23,24 There also needs to be more focus on the impact of armodafinil on daytime sleep, as further disruptions to daytime sleep would feed back to increase sleep pressure and reduce alertness the next day. Additionally, combining armodafinil with evening naps before the night shift may be more effective, as naps in combination with caffeine ingested at the start of a simulated night shift were more effective at increasing alertness than caffeine alone.²⁵ Thus, while the study by Drake and colleagues¹⁷ represents an important step forward, more work is needed. Longer term (≥ 1 month) clinical comparative effectiveness trials of armodafinil versus other wake promoting agents such as caffeine with or without naps, with sufficiently large sample sizes of night workers engaged in actual driving are needed to fully determine the ability of these interventions to reduce the risk of vehicular accidents on the road.

CITATION

Burgess HJ, Reid KJ. Keeping on the straight and narrow. SLEEP 2014;37(12):1887-1888.

DISCLOSURE STATEMENT

The authors have indicated no financial conflicts of interest.