Maximizing Sensitivity of the Psychomotor Vigilance Test (PVT) to Sleep Loss

Mathias Basner,David F Dinges

doi:10.1093/sleep/34.5.581

Abstract

The psychomotor vigilance test (PVT) is among the most widely used measures of behavioral alertness, but there is large variation among published studies in PVT performance outcomes and test durations. To promote standardization of the PVT and increase its sensitivity and specificity to sleep loss, we determined PVT metrics and task durations that optimally discriminated sleep deprived subjects from alert subjects. Repeated-measures experiments involving 10-min PVT assessments every 2 h across both acute total sleep deprivation (TSD) and 5 days of chronic partial sleep deprivation (PSD). Controlled laboratory environment. 74 healthy subjects (34 female), aged 22-45 years. TSD experiment involving 33 h awake (N = 31 subjects) and a PSD experiment involving 5 nights of 4 h time in bed (N = 43 subjects). In a paired t-test paradigm and for both TSD and PSD, effect sizes of 10 different PVT performance outcomes were calculated. Effect sizes were high for both TSD (1.59-1.94) and PSD (0.88-1.21) for PVT metrics related to lapses and to measures of psychomotor speed, i.e., mean 1/RT (response time) and mean slowest 10% 1/RT. In contrast, PVT mean and median RT outcomes scored low to moderate effect sizes influenced by extreme values. Analyses facilitating only portions of the full 10-min PVT indicated that for some outcomes, high effect sizes could be achieved with PVT durations considerably shorter than 10 min, although metrics involving lapses seemed to profit from longer test durations in TSD. Due to their superior conceptual and statistical properties and high sensitivity to sleep deprivation, metrics involving response speed and lapses should be considered primary outcomes for the 10-min PVT. In contrast, PVT mean and median metrics, which are among the most widely used outcomes, should be avoided as primary measures of alertness. Our analyses also suggest that some shorter-duration PVT versions may be sensitive to sleep loss, depending on the outcome variable selected, although this will need to be confirmed in comparative analyses of separate duration versions of the PVT. Using both sensitive PVT metrics and optimal test durations maximizes the sensitivity of the PVT to sleep loss and therefore potentially decreases the sample size needed to detect the same neurobehavioral deficit. We propose criteria to better standardize the 10-min PVT and facilitate between-study comparisons and meta-analyses.

Highlights

These multidimensional features of attention suggest it has a fundamental role in a wide range of cognitive functions, which may be the mechanisms by which sleep loss affects a range of performances, it remains controversial whether impairment due to sleep deprivation is generic to all cognitive processes subserved by attentional processes.[12]
The increase in the average differences outweighed the increase in the standard deviation of the differences, and the effect size increased with increasing psychomotor vigilance test (PVT) duration
This study investigated the effect of PVT task duration and performance outcome metric on the power of the paired t-test to discriminate sleep deprived and alert subjects

Summary

Introduction

There is extensive evidence that the neurobehavioral consequences of sleep loss can be measured in certain aspects of cognitive functioning.[1,2,3] Among the most reliable effects of sleep deprivation is degradation of attention,[2,4] especially vigilant attention as measured by the 10-min psychomotor vigilance test (PVT).[5,6] The effects of sleep loss on PVT performance appear to be due to variability in maintenance of the alert state (i.e., alerting network),[5] and can include deficits in endogenous selective attention,[7,8] but they may occur in attention involved in orienting to sensory events (i.e., orienting network), and attention central to regulating thoughts and behaviors (i.e., executive network).[9,10,11] These multidimensional features of attention suggest it has a fundamental role in a wide range of cognitive functions, which may be the mechanisms by which sleep loss affects a range of performances, it remains controversial whether impairment due to sleep deprivation is generic to all cognitive processes subserved by attentional processes.[12]The PVT5,13-15 has become arguably the most widely used measure of behavioral alertness owing in large part to the combination of its high sensitivity to sleep deprivation[5,6] and its psychometric advantages over other cognitive tests. The standard 10-min PVT measures sustained or vigilant attention by recording response times (RT) to visual (or auditory) stimuli that occur at random inter-stimulus intervals (ISI).[6,13,16,17] It is not entirely accurate to describe the PVT as merely simple RT. The latter is a generic phrase historically used to refer to the measurement of the time it takes to respond to a stimulus with one type of response (in contrast a complex RT task can require different responses to different stimuli). Response time to stimuli attended to has been used since the late 19th century in sleep deprivation research[16,18,19] because it offers a simple way to track changes in behavioral alertness caused by inadequate sleep, without the confounding effects of aptitude and learning.[5,6,15] the 10-min PVT13 has been shown to be highly reliable, with intra-class correlations for key metrics such as lapses measuring test-retest reliability above 0.8.6

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