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Citation
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Filtness AJ, Hickman JS, Mabry JE, Glenn L, Mao H, Camden M, Hanowski RJ. Safety Sci. 2020; 126: e104664. |
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Abstract
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Background
Truck drivers are vulnerable to driver sleepiness due to pressures of shift work and prolonged driving hours; this is a safety concern as sleepiness more than doubles crash risk. Caffeine is a commonly used countermeasure to driver sleepiness. Previous research with truck drivers has demonstrated a positive impact of caffeine consumption on crash risk. However, habitual use of caffeine has the potential to impair night time sleep resulting in increased sleepiness and safety risk. One group that may be particularly vulnerable to the potential negative impacts of high caffeine consumption are those truck drivers who consume ≥ 5 caffeinated drinks per day (≥90th percentile American average daily caffeine consumption).
Method
1,653 self-reported low (1 caffeinated drink per day) and 1,354 high (≥5 caffeinated drinks per day) caffeine consumers were compared across a range of driving safety indicators, health and sleep variables. All drivers completed an initial background questionnaire including the Epworth Sleepiness Scale (ESS), Berlin Questionnaire (BQ) and Dula Dangerous Driving Index (DDDI). Crashes and driving violations were monitored for up to 3 years (depending on enrolment date). Medical Examination Reports were available for 83.0% of the 3,007 participants.
Results
High caffeine consumers were more likely to report poor sleep outcomes: shorter average sleep time, (7.08 h compared to 7.41 h), higher prevalence of excessive daytime sleepiness (7.5% compared to 5.7%) and higher proportion at high risk of obstructive sleep apnoea (OSA) on the BQ (13.1% compared with 9.4%). The higher caffeine consumers were more likely to report negative health behaviours: smoking, alcohol consumption, poor diet and infrequent exercise. Poorer driving safety indicators (negative emotions and aggressive driving on the DDDI) and previous crashes (27.8% compared to 21.6%) were also more common in high than low caffeine consumers.
Conclusion
Caffeine is an effective countermeasure to driver sleepiness, however, high caffeine consumers do not exhibit any benefit to driving safety indicators. In fact, there is some evidence for safety concern because high caffeine consumers self-report more crashes and worse driving safety indicators than low caffeine consumers. High caffeine consumption was associated with poor health behaviours. Further research is needed to fully understand the implications of high caffeine use. Interventions aiming to reduce truck driver sleepiness should be cautious in promotion of caffeine in isolation; a wholistic approach to improve driver health would likely be more effective than focusing on sleep health alone.
Language: en |