|This couple probably didn't have a two huge cups of high-caffeine coffee with 400mg caffeine, each, before bed ;-)|
In the experiment, Drake et al. describe in their latest paper, the researchers made (much to my surprise) a first attempt "to investigate the relative effects of a given dose of caffeine administered at different times of day on subsequent sleep." (Drake. 2013)
Fixed dose (400mg) + varied times
To do so, Drake and his colleagues from the Sleep Disorders & Research Center at the Henry Ford Hospital and the Department of Psychiatry and Behavioral Neurosciences at the Wayne State College of Medicine, in Detroit, as well as a scientist who worked for Zeo Inc in Newton, compared the potential sleep disruptive effects of a fixed dose of caffeine (400 mg) that was administered at 0, 3, and 6 hours prior to habitual bedtime.
|Figure 2: Objectively measured sleep latency (min), total sleep (hrs), wake time (min), sleep efficacy (%), stage 1 & stage 2 sleep (% of total sleep), slow wave and REM sleep times in minutes (Drake. 2013)|
"[t]he magnitude of reduction in total sleep time suggests that caffeine taken 6 hours before bedtime has important disruptive effects on sleep and provides empirical support for sleep hygiene recommendations to refrain from substantial caffeine use for a minimum of 6 hours prior to bedtime." (Drake. 2013)For the PM-trainees and pre-workout fanatics among the SuppVersity readers this probably sounds scary. Stimulant-laden preworkout products are yet not the only offenders that could compromise your sleep hygiene.
|"1kg Body Fat in 4 Weeks From < 2x Energy Drinks per Day!" | more|
"This must be a mistake. The must be an 'on the other hand' attached!"
You are right, the news are in fact so "bad" that I decided it may be worth digging a little further to see, if I, an outspoken coffee concessionaire, can't find a glitch in this or a conflict to another study that would put a relieving "?" behind the results of the study at hand:
- Statistical significance vs. real-world effects - While it is not a real glitch, it's certainly questionable how great real-world health consequences of the bordeline significant decrease in sleep efficacy and the significant 32% reduction in slow wave sleep actually are. With respect to the generic quantity "sleep quality", we could probably say that we give a damn. The loss of 15-22 minutes of slow wave sleep, of which scientists say that it is the time, when we consolidate new memories and our brain recovers from the daily activities, the 32% reduction in slow wave sleep does begin to sound scary. If we also take into account that Tasali et al. observed that ...
"[...] all-night selective suppression of SWS, without any change in total sleep time, results in marked decreases in insulin sensitivity without adequate compensatory increase in insulin release, leading to reduced glucose tolerance and increased diabetes risk" (Tasali. 2013)in young, perfectly healthy subjects, I am not quite sure, if the overall beneficial metabolic and cognitive effects still outweigh the potential detriments that arise from the consumption of high amounts of caffeine shortly before going to bed.
Figure 3: According to Blanchard et al. it can take up to 15h to get rid of 5mg/kg body weight caffeine.Previous dose-response studies, demonstrate that increasing doses of caffeine administered at or near bedtime are associated with significant sleep disturbance (Karacan. 1976; Lasagna. 1977; Yanik. 1987) and the recommendations to avoid caffeine close to bedtime is in every list of sleep hygiene practices. However, evidence is less clear regarding the consumption of caffeine at earlier time.
- The "Ah, I am used to it hypothesis" - Being "used" as you may have gotten to the sleep disruptive effects of caffeine does not equate being "immune" to them. That's at least what the 36 healthy male and female habitual caffeine consumers in a 1998 study by Jack E. James had to realize, when they skipped on their beloved caffein for just one day and their sleep duration and quality increased significantly ().
Coffee only in the AM!?
The time our bodies need to get rid of 50% of the caffeine we've consumed at T = 0 ranges from 2.7-9.9 hours (Blanchard. 1983a,b). According to Blanchard et al. 'the average' 22-year old needs ~15h to get rid of all the caffeine that made it into his / her bloodstream after the consumption of ca. 400mg caffeine. If you wanted to make perfectly sure that your coffee consumption does not compromise your sleep, it would thus appear advisable to drink your 3-4 cups of coffee in the morning.
In the absence of studies that have compared the sleep disruptive effects of caffeine given at different times before bed it does however remain unclear it remains unclear when exactly the 'coffee curfew' should begin.
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