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Journal Watch: Alertness in the Air

Reviewed This Month

Impact of Shift Duration on Alertness Among Air-Medical Emergency Care Clinician Shift Workers

Authors: Patterson PD, Weaver MD, Markosyan MA, et al. 

Published in: Am J Ind Med, 2019 Apr; 62(4): 325–36.  

Most of us work shifts, and an abundance of research links shift work to negative outcomes that can include health problems, medical errors, and sleepiness or fatigue. This research led to the development of evidence-based guidelines for fatigue risk management in EMS, published in Prehospital Emergency Care. One of the recommendations these authors developed was that EMS personnel should work shifts of less than 24 hours. 

However, much of the research into shift work and fatigue in EMS is focused on providers who work in ground transport. There is limited research focused on the air-medical setting. 

This month’s study followed air-medical clinicians for two weeks and collected data on alertness at the start and end of their 12- or 24-hour shifts. The authors’ hypothesis was that “performance on a behavioral test of alertness following shifts lasting 24 hours is worse than alertness following shifts lasting 12 hours.”

Study Design

This was a prospective observational cohort study. Potential participants were recruited by e-mail from June 2015 to March 2016. They came from four large services located in the Midwestern, Northeastern, and Southern regions of the United States. To be eligible to participate, air-medical clinicians had to be at least 18 years old, working for one of the four study sites, working either 12- or 24-hour shifts, and willing to participate in the study.

Willingness to participate might sound obvious, but it’s an important criterion. When you’re studying subjects prospectively, it is necessary to obtain written informed consent from participants. Without that, an institutional review board is unlikely to approve the project. This study obtained IRB approval from all four study sites. 

Each participant agreed to wear an actigraph. An actigraph monitors human rest and activity cycles. The participants also completed a baseline survey providing information on their sleep quality, overall sleepiness, and fatigue and recovery. The survey also collected demographic information.

Participants then completed a three-minute psychomotor vigilance test at the beginning and end of at least one shift. The test involved the participant tapping on a tablet screen when a number appeared. Measures evaluated from this test included the mean response time, number of lapses, and speed. Participants completed a diary that captured intershift recovery, daily shift work, daily sleep hours, and daily subjective sleep quality. 

For analysis the authors compared those who worked 12-hour shifts to those who worked 24-hour shifts. To account for clinicians being held over due to a late dispatch or early arrival, the authors categorized participants into two groups: 24 hours and less than 24 hours. Through the actigraphs and sleep diaries, they compared hours of sleep before, during, and after shifts with the primary outcome of interest being performance on the psychomotor vigilance test. 


There were 112 unique individuals who participated in the study. There were 26 who participated twice. The average number of days for which participants completed sleep diaries was 13. Participants wore the actigraphs most of the time, an average of 21.6 hours per day. Complete sleep diary and actigraph data was obtained from 92% of participants.

There were 46% of participants who worked shifts of less than 24 hours, and 54% who worked 24-hour shifts. Of these, 76% were exactly 12 hours, and 97% were exactly 24 hours. The average nap or sleep time while on duty for sub-24-hour shifts was 2.6, and the average for 24-hour shifts was 7.3. 

When only evaluating the individuals who participated once, the average age of participants was 43.4 years, and the population was 42% female. Most participants were prehospital nurses (56%), followed by paramedics (37%) and respiratory therapists (7%). More than three-quarters worked full time (76%), and over half (52%) held more than one job. Participants reported either good (51%) or excellent (49%) health, with no one reporting their health as fair or poor. A plurality (49%) had a BMI consistent with being overweight, and 21% had a BMI consistent with being obese. 

When evaluating sleep and fatigue-related metrics, 55% had poor sleep quality, but 70% were categorized as unlikely to be abnormally sleepy, and no participants were categorized with excessive sleepiness. There were 41% of participants classified as fatigued. 

When evaluating the psychomotor vigilance test, there was no difference in alertness comparing the sub-24-hour group to the 24-hour group. 


The authors had to reject their hypothesis and conclude there was no difference. This is certainly a surprising result, given previous studies. However, let’s review some of this study’s results to put this into context. 

At baseline this was not a very sleepy cohort. They were in good health, and—what may be most important—those who worked 24 hours were provided the ability to sleep an average of 7-plus hours while on duty. Additionally, as the authors point out, the psychomotor vigilance tests were administered at the starts and ends of shifts. The majority of these tests were administered at or before 9 a.m. and again around 6 p.m. This aligns with the normal human circadian rhythm, potentially confounding the results. So while the results are surprising, they may be skewed by the convenience sample and time of the psychomotor vigilance testing. 

The survey was also voluntary. Therefore, the results likely can’t be generalized to all air-medical systems, and those who chose to respond may be different than those who did not choose to respond. Further, the authors did not collect data on caffeine use. 

This is an interesting study that adds to the limited literature on air-medical EMS provider fatigue. I hope we can see it replicated to validate the results.    

Antonio R. Fernandez, PhD, NRP, FAHA, is research director at the EMS Performance Improvement Center and an assistant professor in the Department of Emergency Medicine at the University of North Carolina–Chapel Hill. He is on the board of advisors of the Prehospital Care Research Forum at UCLA.

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