Sleep Smarter: 21 Essential Strategies to Sleep Your Way to a Better Body, Better Health, and Bigger Success

by Shawn Stevenson

Your body is still producing more and more adenosine because of all the “awake” activities you’re doing, but the adenosine never gets properly metabolized. As a result, your body literally has to change the way it normally functions, stress hormone levels increase in your system, and your brain and organs get overworked because they aren’t getting the accurate cues to rest and recover. Because of caffeine’s long-term effects, it can take several days for its aftermath to wear off. Caffeine has a half-life of around 5 to 8 hours (depending upon your unique biochemical makeup). Half-life essentially means that after a specific amount of time (say, 8 hours), half of the substance is still active in your system. So, using the 8-hour half-life as an example, if you consumed 200 milligrams of caffeine (which is equivalent to about one or two cups of standard coffee), after 8 hours, you’d have half of it (or 100 milligrams) active in your system; after another 8 hours, you’d have 50 milligrams; after another 8 hours, it would be 25 milligrams; and so on. This is why having caffeine even 6 hours out from bedtime still caused sleep disturbances in the study.