Marked sleepiness occurs during typical night shift work hours and this reduced alertness is associated with marked performance deficits. The effect of caffeine (versus placebo) upon sleepiness at night was studied using objective measures of physiological sleep tendency and ability to sustain wakefulness. Both measures show caffeine to reduce sleepiness at a single dose roughly the equivalent of two to four cups of coffee. Despite impressive objective differences in alertness with caffeine, subjects did not consistently differentiate between drug conditions on subjective alertness assessments. The use of CNS stimulants to promote alertness during night shift hours should be considered, particularly for occupations for which alertness is critical.

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SUMMARY  Hypnotic medication reliably improves sleep during the day, in terms of increasing total sleep time (TST) and reducing awakenings and light sleep. Middle‐aged individuals may benefit more than young adults. In addition, the time of day during which sleep is attempted may influence the efficacious dose of short‐acting drugs. Available data suggest that improving sleep during the day may improve alertness/performance at night to a mild degree, but significant circadian‐related sleepiness remains. Hypnotic medication may help minimize the cumulative effects of sleep loss associated with daytime sleep. Use for more than one week has not been adequately studied; however, as most night and rotating workers' schedules allow for night‐time sleep for two or more nights per week, available evidence indicates that hypnotics can be used effectively on an intermittent basis, e.g. for the first 2–4 day‐sleep periods of night shifts. Caffeine has been shown to increase alertness and improve psychomotor performance during usual night‐shift hours when taken between 22.30 and 01.20 hours. Available data indicate that at approximate dosages of 250–400 mg, the beneficial effects persist until at least 05.30 hours. For most subjects, caffeine taken at the start of the night‐shift does not interfere significantly with daytime sleep beginning at 09.00 hours. There is also some evidence that single doses of caffeine at the beginning of a night shift may be more alerting than divided doses. If caffeine is to be used therapeutically, avoidance of social use may be required to avoid tolerance to CNS stimulant effects. Despite the positive results of laboratory research examining hypnotics or caffeine as shiftwork countermeasures, field trials have not been conducted.