A shot of caffeine can reduce potentially disastrous mistakes made by drowsy shift workers, research has shown.
People who work unsocial hours or through the night may suffer a form of "jet lag" due to disruption of their body clock rhythms.
As a result they can become very sleepy when working and prone to mishaps. For some, such as lorry drivers or doctors, this can have serious consequences.
The new study reviewed data from 13 trials investigating the effects of caffeine on shift worker performance.
Caffeine was administered in coffee, "pep" pills, energy drinks, or caffeinated foods, mostly in simulated working conditions.
In some trials performance was assessed by carrying out tasks such as driving. Others subjected volunteers to neuropsychological tests.
Caffeine appeared to reduce errors more than "dummy" placebo treatments or naps, according to the results published in the Cochrane Database of Systematic Reviews.
It also improved performance in various tests, including those of memory, attention, perception, conceptualising and reasoning.
Lead researcher Dr Katherine Ker, from the London School of Tropical Medicine, said: "It seems reasonable to assume that reduced errors are associated with fewer injuries, although we cannot quantify such as reduction."
The average age of people taking part in the trials was between 20 and 30.
Because the effects of body clock disruption vary with age, more research is needed to see if caffeine improved the alertness of older workers, said the scientists.