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Coffee & Health

Systematic-Review and Meta-analysis of the Effects of Caffeine in Fatigued Shift Workers: Implications for Emergency Medical Services Personnel

J L Temple et al, 2018.
Prehosp Emergency Care, published online.
January 15, 2018



Emergency Medical Services (EMS) workers may experience fatigue as a consequence of shift work. We reviewed the literature to determine the impact of caffeine as a countermeasure to fatigue in EMS personnel and related shift workers.


We employed the GRADE methodology to perform a systematic literature review and search multiple databases for research that examined the impact of caffeine on outcomes of interest, such as patient and EMS personnel safety. For selected outcomes, we performed a meta-analysis of pooled data and reported the pooled effect in the form of a Standardized Mean Difference (SMD) with corresponding 95% confidence intervals.


There are no studies that investigate caffeine use and its effects on EMS workers or on patient safety. Four of 8 studies in shift workers showed that caffeine improved psychomotor vigilance, which is important for performance. Caffeine decreased the number of lapses on a standardized test of performance [SMD = 0.75 (95% CI: 0.30 to 1.19), p = 0.001], and lessened the slowing of reaction time at the end of shifts [SMD = 0.52 (95% CI: 0.19 to 0.85); p = 0.002]. Finally, 2 studies reported that caffeine reduced sleep quality and sleep duration.


Although the quality of evidence was judged to be low to moderate, when taken together, these studies demonstrate that caffeine can improve psychomotor performance and vigilance. However, caffeine negatively affects sleep quality and sleep duration. More systematic, randomized studies need to be conducted in EMS workers in order to address the critical outcomes of health and safety of EMS personnel and patients. The risk/benefit ratio of chronic caffeine use in shift workers is currently unknown.

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