What most people (including us before Camille explained it to Jake) don’t realize is that the half-life of caffeine is five to six hours. So if the average person has a coffee at 4 p.m., half the caffeine is out of the bloodstream by 9 or 10 p.m., but the other half is still around. The upshot is that at least some caffeine is blocking at least some adenosine receptors for many hours after you have caffeine and very possibly interfering with your sleep and in turn the next day’s energy.
