case, the visual performance of soldiers in combat could be impaired in low illumination situations. There is strong evidence that smoking accelerates hearing loss associated with aging and interacts with ambient noise to increase this risk.

Vigilance and Cognitive Function

Visual and auditory vigilance is important in military performance, particularly during tedious tasks in which detection of infrequent events is critical, such as watch duty. In general, nicotine appears to enhance vigilance in repetitive tasks acutely, and deprivation of nicotine is associated with substantial decrements in vigilance and cognitive function (Hirshman et al., 2004; Mancuso et al., 2001). Thus, in deployment circumstances in which military personnel are unable to smoke, nicotine withdrawal may impair performance.

Motor-vehicle driving simulation studies show that deprived smokers have longer reaction times and more driving errors than nonsmokers and nondeprived smokers (Heimstra et al., 1967). Similar findings have been observed in various reaction-time tasks (Frankenhaeuser et al., 1971; Myrsten et al., 1972). Smoking allows better performance in the later stages of vigilance tasks (Wesnes and Warburton, 1978). Nonsmokers outperform nicotine-deprived smokers in rapid information-processing tasks (Taylor and Blezard, 1979). Hill et al. (2003) reported that subjects who had never smoked cigarettes outperformed current smokers significantly in two cognitively demanding tasks: block design and free recall. Poorer performance was correlated with higher frequency and longer duration of cigarette-smoking. Performance in less demanding tasks, such as general knowledge and word comprehension, was not significantly different between the two groups. Nonsmoking university students were better able than nonsmokers to detect signals in an auditor-vigilance task (Tong et al., 1977).

Aviation Performance

Pilots require a high level of cognitive function, vigilance, short reaction time, and rapid decision-making for optimal flight safety. Pilots who are regular smokers may experience withdrawal effects during flight that may impair performance and threaten safety (Sommese and Patterson, 1995). Mertens et al. (1983) examined the effects of not smoking for 4 hours on 17 habitual smokers who were taking the Civil Aeromedical Institute multiple-task performance battery at a simulated cabin altitude of 6,500 ft. Not smoking impaired performance, particularly tracking performance, which is a function that is thought to be important in flying (Mertens et al., 1983). Giannokoulas et al. (2003) studied 20 experienced pilots in the Greek Air Force who smoked an



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