Impaired performance in commercial drivers: role of sleep apnea and short sleep duration

Abstract

Sleepiness plays an important role in major crashes of commercial vehicles. Because determinants are likely to include inadequate sleep and sleep apnea, we evaluated the role of short sleep durations over 1 wk at home and sleep apnea in subjective sleepiness (Epworth Sleepiness Scale), objective sleepiness (reduced sleep latency as determined by the Multiple Sleep Latency Test), and neurobehavioral functioning (lapses in performance, tracking error in Divided Attention Driving Task) in commercial drivers. Studies were conducted in 247 of 551 drivers at higher risk for apnea and in 159 of 778 drivers at lower risk. A multivariate linear association between the sets of outcomes and risk factors was confirmed (p < 0.0001). Increases in subjective sleepiness were associated with shorter sleep durations but not with increases in severity of apnea. Increases in objective sleepiness and performance lapses, as well as poorer lane tracking, were associated with shorter sleep durations. Associations with sleep apnea severity were not as robust and not strictly monotonic. A significant linear association with sleep apnea was demonstrated only for reduced sleep latency. The effects of severe apnea (apnea-hypopnea index, at least 30 episodes/h), which occurred in 4.7%, and of sleep duration less than 5 h/night, which occurred in 13.5%, were similar in terms of their impact on objective sleepiness. Thus, addressing impairment in commercial drivers requires addressing both insufficient sleep and sleep apnea, the former being more common.

Figure 1.

Least-squares estimates of mean Multiple Sleep Latency Test (MSLT) with standard errors controlling for apnea severity category, sleep duration category, age, sex, and body mass index. (A) Apnea–hypopnea index category. (B) Mean length of cumulative duration of relative inactivity.

Figure 2.

Percentages of subjects with MSLT values of less than 5 min, 5 to less than 10 min, and 10 min or more in different categories of severity of sleep apnea. Percentages were determined on the basis of weighted data. The line connects the percentages with pathologic sleepiness, that is, MSLT < 5 min.

Figure 3.

Percentages of subjects with MSLT values of less than 5 min, 5 to less than 10 min, and 10 min or more in different categories of cumulative duration of relative inactivity (hours). The line connects the percentages in each group with MSLT < 5 min.

Figure 4.

Predicted mean Psychomotor Vigilance Task (PVT) lapses per trial, controlling for apnea severity category, sleep duration category, age, sex, and body mass index. Statistical comparisons were performed on transformed data. Predicted values are reexpressed on the original scale to enhance interpretability. The magnitudes of the standard error bars are proportional to the ratio of the standard error to predicted value on the transformed scale to provide an accurate assessment of statistical precision. (A) Categories of severity of sleep apnea, as measured by apnea–hypopnea index. (B) Categories for sleep duration at home (mean cumulative duration of relative inactivity).

Figure 5.

Predicted mean absolute tracking errors on the Divided Attention Driving Task controlling for apnea severity category, sleep duration category, age, sex, and body mass index, and expressed on the original scale (centimeters). Statistical comparisons were performed on transformed data. Predicted values are reexpressed on the original scale to enhance interpretability. Magnitudes of the standard error bars are proportional to the ratio of the standard error to predicted value on the transformed scale to provide an accurate assessment of statistical precision. (A) Categories of severity of sleep apnea as judged by apnea–hypopnea index. (B) Categories of sleep duration at home (mean cumulative duration of relative inactivity).