With hours-of-service rules suspended for select drivers due to the coronavirus pandemic, many will drink more coffee to stay alert. While high-caffeine consumption is OK in the short term, long-term usage is associated with more truck crashes, according to a recently published study.
Nearly 6% more truck drivers who drink large amounts of coffee or energy drinks reported having had a crash in the previous three years than those drivers who consume smaller amounts, according to a UK researcher who studied 3,000 US drivers in eight states.
The study, led by Ashleigh Filtness, PhD., a lecturer in transport safety at Loughborough University Design School in Leicestershire, United Kingdom, noted that those drivers who drank five cups or more daily (which would put drivers is in the 90th percentile of the U.S. average daily caffeine consumption) also reported lower overall health, poorer sleep, drank more alcohol, smoked and had poor diets.
In studies like this, a correlation may not always mean causation. In other words, drinking lots of coffee may not be the sole contributor to these reported increased crashes and health conditions but may instead be a key contributor to an unhealthy lifestyle which in turn can cause crashes.
"The analysis undertaken was looking for associations, so it is not possible to comment on causality," Filtness told Fleet Owner. "It is probable that many factors about driver health combine to influence crash risk and driving safety. Because of the association between negative health behaviors and caffeine use, it is recommended to take a holistic approach to improve driver health more broadly, rather than specifically targeting sleepiness."
Filtness is not advocating cutting out coffee or energy drinks entirely. "I have been studying driver sleepiness for the past 12 years,” she said. “There is strong research evidence for the short-term benefits of caffeine to help reduce drivers’ experience of sleepiness. The more work I do in the area, the more I have anecdotally heard stories of professional drivers who are regularly consuming high quantities of caffeine in order to keep going."
This led her to look more closely at drivers who drink coffee to better understand its effects. In doing so, she learned about the other conditions surrounding high consumption coffee drinkers and that 27.8% of all the high caffeine consumers had had a crash in the previous three years — compared to 21.6% for low drinkers.
Researchers collected data through questionnaires and medical reports from drivers in Illinois, Ohio, Kentucky, New Jersey, Virginia, Georgia, Texas and California. From a pool of 11,000 drivers, they found 3,007 individuals who met the coffee consumption criteria and then divided them into high coffee users (more than 5 cups a day) and low caffeine users (1 cup per day). Those in the middle were purposely eliminated so that researchers could have two very distinct groups to study.
The participants were asked how many cups/glasses/pills of coffee or other caffeinated products they consumed daily. "This was not restricted to coffee, although coffee was the most commonly reported drink," she said. "The individual answers of each participant were not reported back to their employer. Although there will always be some limitations to self-report data, it is hoped that the anonymous and independent setting encouraged drivers to report truthfully," she added.
Filtness, who did this study in partnership with Virginia Tech Transport Institute (VTTI), said: "This is one of the first occurrences of large-scale documentation of caffeine consumer behavior in truck drivers. It is difficult to monitor the impact of caffeine in the real world because caffeine content in brewed drinks is not standardized, therefore, the majority of caffeine and driving studies have been conducted in laboratory settings which are great for telling us about how people respond to caffeine but are unable to demonstrate how people use caffeine in their daily lives."
More work needs to be done, Filtness noted, in order to further understand the impact of caffeine products on driver safety. "A greater granularity of detail would help to be able to profile different types of caffeine consumer, e.g. to compare between preference for different types or drink, or to compare intake on work vs. non-work days. It is also of interest to identify at what number of drinks per day the tipping point into increased unhealthy behaviors might be. It would be beneficial to objectively monitor caffeine intake in truck drivers to observe longer-term outcomes."
The study associations between high caffeine consumption, driving safety indicators, sleep and health behaviors in truck drivers was published in the June 2020 issue of the journal Safety Science.