A brief period of sleep of around 15 to 20 minutes, preceded by consuming a caffeinated drink or another stimulant, may combat daytime drowsiness more effectively than napping or drinking coffee alone.    A stimulant nap (or coffee nap, caffeine nap, occasionally napuccino)  was discovered by British researchers, Horne and Reyner, to be more effective than regular naps in improving post-nap alertness and cognitive functioning.   In a driving simulator and a series of studies, Horne and Reyner investigated the effects of cold air, radio, a break with no nap, a nap, caffeine pill vs. placebo and a short nap preceded by caffeine on mildly sleep-deprived subjects. A nap with caffeine was by far the most effective in reducing driving accidents and subjective sleepiness as it helps the body get rid of the sleep-inducing chemical compound adenosine .  Caffeine in coffee takes up to half an hour to have an alerting effect, hence "a short (<15min) nap will not be compromised if it is taken immediately after the coffee."    One account suggested that it was like a "double shot of energy" from the stimulating boost from caffeine plus better alertness from napping.  This procedure has been studied on sleep-deprived humans given the task of driving a motor vehicle afterwards,  although it has not been studied on elderly populations.