Use of caffeinated substances and risk of crashes in long distance drivers of commercial vehicles: case-control study OPEN ACCESS

Objective To determine whether there is an association between use of substances that contain caffeine and the risk of crash in long distance commercial vehicle drivers. Design Case-control study. SettingNew SouthWales (NSW) andWestern Australia (WA), Australia. Participants 530 long distance drivers of commercial vehicles who were recently involved in a crash attended by police (cases) and 517 control drivers who had not had a crash while driving a commercial vehicle in the past 12 months. Main outcome measure The likelihood of a crash associated with the use of substances containing caffeine after adjustment for factors including age, health disorders, sleep patterns, and symptoms of sleep disorders as well as exposures such as kilometres driven, hours slept, breaks taken, and night driving schedules. Results Forty three percent of drivers reported consuming substances containing caffeine, such as tea, coffee, caffeine tablets, or energy drinks for the express purpose of staying awake. Only 3% reported using illegal stimulants such as amphetamine (“speed”); 3,4 methylenedioxymethamphetamine (ecstasy); and cocaine. After adjustment for potential confounders, drivers who consumed caffeinated substances for this purpose had a 63% reduced likelihood of crashing (odds ratio 0.37, 95% confidence interval 0.27 to 0.50) compared with drivers who did not take caffeinated substances. Conclusions Caffeinated substances are associated with a reduced risk of crashing for long distance commercial motor vehicle drivers. While comprehensive mandated strategies for fatigue management remain a priority, the use of caffeinated substances could be a useful adjunct strategy in the maintenance of alertness while driving. Introduction Long distance drivers of commercial motor vehicles routinely experience monotonous and extended driving periods in a sedentary position; this, combined with the disruption to circadian rhythms linked to the common requirement of night driving, has been associated with wake time drowsiness. 2 Alertness is critical to safety for the driver and other road users as lapses of vigilance in relation to the task of driving can increase the likelihood of crashing. 4 Many strategies are available to long distance drivers to maintain their alertness, and studies have identified positive benefits from the use of stimulants such as caffeine. We investigated the effects of use of caffeinated substances on the likelihood of a crash among long distance drivers of commercial motor vehicles. Caffeine is a psychostimulant that works by suppressing the innate adenosine mediated drive to sleep while activating arousal 8 and is one of the most commonly consumed stimulants worldwide. It has been shown to increase alertness in shift workers and improve the capacity for task performance.When used in excess, however, caffeine can also affect the quantity and quality of sleep, as sleep latency is prolonged and slow wave sleep is reduced. The effectiveness of caffeine for enhancing alertness in the performance of monotonous tasks has previously been shown in laboratory and driving simulator settings. 12 Some authors have raised concerns about the methods used in these studies—namely, that the effects seen in comparisons of caffeine and placebo groups are simply an exaggerated response to caffeine withdrawal because of caffeine deprivation before the test and not caused by the substance alone. In contrast, a recent study used a field setting and found that a combination of caffeine and naps improved performance and alertness for night workers, and Mets and colleagues 16 Correspondence to: L N Sharwood, 98 Bunnerong Rd, Pagewood, NSW 2035 Australia [email protected] No commercial reuse: See rights and reprints http://www.bmj.com/permissions Subscribe: http://www.bmj.com/subscribe BMJ 2013;346:f1140 doi: 10.1136/bmj.f1140 (Published 20 March 2013) Page 1 of 7