Validating and extending the three process model of alertness in airline operations

PLoS One. 2014 Oct 20;9(10):e108679. doi: 10.1371/journal.pone.0108679. eCollection 2014.

Abstract

Sleepiness and fatigue are important risk factors in the transport sector and bio-mathematical sleepiness, sleep and fatigue modeling is increasingly becoming a valuable tool for assessing safety of work schedules and rosters in Fatigue Risk Management Systems (FRMS). The present study sought to validate the inner workings of one such model, Three Process Model (TPM), on aircrews and extend the model with functions to model jetlag and to directly assess the risk of any sleepiness level in any shift schedule or roster with and without knowledge of sleep timings. We collected sleep and sleepiness data from 136 aircrews in a real life situation by means of an application running on a handheld touch screen computer device (iPhone, iPod or iPad) and used the TPM to predict sleepiness with varying level of complexity of model equations and data. The results based on multilevel linear and non-linear mixed effects models showed that the TPM predictions correlated with observed ratings of sleepiness, but explorative analyses suggest that the default model can be improved and reduced to include only two-processes (S+C), with adjusted phases of the circadian process based on a single question of circadian type. We also extended the model with a function to model jetlag acclimatization and with estimates of individual differences including reference limits accounting for 50%, 75% and 90% of the population as well as functions for predicting the probability of any level of sleepiness for ecological assessment of absolute and relative risk of sleepiness in shift systems for safety applications.

Publication types

  • Research Support, Non-U.S. Gov't
  • Validation Study

MeSH terms

  • Acclimatization
  • Adult
  • Aviation*
  • Circadian Rhythm
  • Fatigue / physiopathology
  • Female
  • Humans
  • Male
  • Models, Biological*
  • Probability
  • Risk Assessment
  • Safety
  • Sleep / physiology
  • Wakefulness* / physiology

Grants and funding

The study was partly funded by Vinnova Sweden (to Stress Research Institute) (www.vinnova.se) and partly by Jeppesen AB. The funder Vinnova had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Co-authors Tomas Klemets and David Karlsson are employed by the funder Jeppesen AB. Jeppesen AB provided support in the form of salaries for authors TK and DK, but did not have any additional role in the study design, data collection and analysis, decision to publish, or preparation of the manuscript. Co-author Stephen Hough is employed by Scandinavian Airline Systems AB. Scandinavian Airline Systems AB provided support in the form of salaries for author SH, but did not have any additional role in the study design, data collection and analysis, decision to publish, or preparation of the manuscript. The specific roles of these authors are articulated in the ‘author contributions’ section.