The caffeine in coffee is a mild stimulant, which acts positively in this respect. As the caffeine in coffee helps enhance alertness and attentiveness, this can lead to better performance at work as well as improve overall mood and it also works against fatigue.

There are many external stimuli, which may affect how long it takes someone to get to sleep. Some people experience a (mild) stimulating effect of caffeine when coffee is consumed shortly before going to bed. The effects are, however, very much individual-dependent. Some people find it hard to sleep after one cup in the early evening, whereas other people can drink coffee all evening without any effect on sleep. Anyone who is particularly sensitive can simply switch to decaffeinated coffee during the evening. There is no evidence to suggest that caffeine affects the quality of sleep, or different phases of sleep during the night.