Caffeine lovers sleep less but more deeply

 

Caffeine reduces sleep duration, yet the body finds a way to compensate for the loss:

People who consume four or more caffeinated drinks a day sleep less on average than those who consume three or fewer. The most reliable estimates place the difference at around 11–13 minutes per day. 

However, subjective sleep quality and the tendency to be an "early bird" or a "night owl" were not affected by caffeine intake.

On the other hand, those who regularly consume large amounts of caffeine exhibited deeper slow-wave sleep—likely because the body partially compensates for the reduction in duration.

 Scientists attribute this to increased brain delta activity during sleep.

 Other neurophysiological and EEG studies show that caffeine often decreases slow-wave activity (deep sleep) and promotes a lighter, more wake-like brain pattern, meaning sleep may feel normal while being less restorative.