Assessing performance upon abrupt awakening from naps during quasi-continuous operations

Abstract

Quasi-continuous work settings often involve sleep loss and requirements to perform at unpredictable times. Napping may alleviate some of the sleep-loss problems, but it increases the risk that the person will have difficulty functioning upon abrupt awakening. This paper describes an experimental approach, techniques, and analyses for investigating performance upon abrupt awakening from 2-h naps placed near either the circadian peak (P) or trough (T) in body temperature and preceded by 6, 18, 30, 42, or 54 h of sleep deprivation. Five groups of healthy young adults performed quasi-continuously for 54 h and were permitted a 2-h nap at one of five times. Reaction time (RT) to answer a phone terminating the nap, subjective estimates, and performance of a brief, challenging cognitive task were related to nap-sleep parameters of each group. Sleep deprivation increased the amount of deep sleep in the naps, and this was associated with greater postnap cognitive performance decrements; subjective estimates were unaffected, and RT performance was related simply to stage of sleep prior to awakening. Circadian placement of the naps also modulated the postnap cognitive decrement: T naps produced greater cognitive decrements than P naps, even when the latter involved more prior sleep loss. These findings have both practical and theoretical significance for evaluating the awakening process, and would not have been possible without the approach, techniques, and procedures described.There is a fundamental dilemma faced in planning sleep logistics for quasi-continuous work situations, such as those often encountered in the military. The person may have to perform at full capacity, at a moment's notice, at unpredictable times, over a period of many days, weeks, or months. If the individual is kept awake throughout the period, the inevitable effects of sleep deprivation take their toll, performance deteriorates, and involuntary sleep onsets become commonplace. If, on the other hand, the person sleeps, performance upon abrupt awakening from sleep may be severely compromised.Paradoxically, people actually function less well immediately upon awakening from sleep than they do prior to going to sleep (Kleitman, 1963), although the detrimental effect does not usually last beyond 15 to 30 min after subjects awaken. Decreased performance upon sudden awakening from sleep has been shown to occur for a broad range of tasks, including simple reaction time (RT) (Dinges, Orne, Evans, & Orne, 1981;Okuma, Nakamura, Hayashi, & Fujimori, 1966 Gillberg, 1979;Bonnet, 1983;Grosvenor & Lack, 1984;Stones, 1977), time estimates (Carlson, Feinberg, & Goodenough, 1978), complex-behavior simulation tasks Hartman, Langdon, & McKenzie, 1965;Langdon & Hartman, 1961;Seminara & Shavelson, 1969), and a number of cognitive tasks, such as mental arithmetic, cancellation, and clock reversal (Dinges et al., 1981;Fort & Mills, 1972; Pritchett, 1964 Pritchett, /1969Scott, 1969;Tebbs, 1972; Wilkinson & Stretton, 1971).Not only is the immediate postsleep performance dec...

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