The Prediction of Cognitive Performance Degradations during Sustained Operations

Abstract

Opportunities for fatigue related accidents are greatest when extended duty cycles must be maintained. A means to plan for the influence of fatigue would be useful to best utilize crew resources. Equations were derived to predict performance degradations associated with fatigued cognitive abilities. During a 30-hour sleep deprivation study, nine male subjects were required to perform a 45-minute cognitive performance battery every 120 minutes. Plasma melatonin levels also were obtained. Cognitive performance measures sensitive to fatigue were determined and used to derive composite response time and accuracy scores. The equations that best described the composite scores included a linear component (hours awake weighting) and a circadian component (melatonin weighting). The respective prediction equations accounted for 33% of the variance in response time performance (p < .0001) and 18% of the variance in accuracy performance (p < .0005). Tests on the beta weights indicated that accuracy predictions were more enhanced by the circadian component than were those for response time. This work represents a mathematical description of fatigued performance that is sensitive to circadian cycles and requires minimal input data. The results might be used to recommend the best crew rest times and when additional crew should be employed as individual performance falls below critical thresholds during sustained operations.