A new study finds that chronic caffeine consumption has surprising effects on sleep patterns and brain blood flow in mice, increasing brain blood flow during sleep. The study, led by Dr. Andrew Charles of UCLA, was conducted using a minimally invasive microchip and video recording system, which allowed the mice to remain freely moving while it recorded various physiological and behavioral parameters over extended periods, ranging from weeks to months. This enabled the researchers to examine the effects of chronic caffeine consumption on the timing of sleep, (including REM sleep), as well as on brain blood flow in the wake and sleep states.
The study found that mice consistently have a “siesta” during the latter part of their awake phase. Daily caffeine abolished this siesta and consolidated wakefulness during the awake phase. It also shifted the onset of sleep (particularly REM sleep) by up to 2 hours relative to the light dark cycle. Interestingly, the mice that consumed caffeine when awake slept more solidly, and their overall amount of non-REM and REM sleep was not changed because they “slept in” later.