Thursday, February 19, 2015

10h of Catch-Up Sleep Can Ameliorate the Negative Effects of Sleep Restriction on Insulin Sensitivity in Healthy Men

Can you partly redeem your sleep dept on the weekend? First study to investigate this question in clinical trial suggests: Yes you can! At least to a certain extent.
In today's installment of the short news I am going to take a closer look at the surprising results of a recent study from the University of Sydney (Killick. 2015). A study which may offer some relief to those of you who are for one reason or another not getting enough sleep on a regular basis.

If that sounds like you, you may be interested to hear what happened to the healthy male 18-50-year old subjects in the latest study from the University of Sydney. A study the objective of which was to determine whether the ill effects of acute sleep restrictions on insulin sensitivity in healthy individuals could be leveled by recovery or a few nights spend on "catch-up sleep" (10h per night).
Learn more about the health effects of correct / messed up circadian rhythms

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Breaking the Fast to Synchronize the Clock

Fasting (Re-)Sets the Peripheral Clock

Vitamin A & Caffeine Set the Clock

Pre-Workout Supps Could Ruin Your Sleep
To this ends, the participants underwent 2 out of 2 or 3 potential study conditions, in a randomised order, two period crossover design. The three potential study conditions were 3 weekend nights (Friday night to Monday morning) of (A) 10h time in bed (TIB) each night, (B) 6h TIB each night or (C) 10h TIB with slow-wave-sleep (SWS) suppression by acoustic stimuli (10h↓SWS) each night. Those aged ≤35 years (group 1) could be randomised to any 2 of the 3 conditions. Those >35 years (group 2) could only be randomised to Condition A (6h TIB) or Condition B (10h TIB). Men >35 years were not randomised to Condition C (10h↓SWS) because SWS is already reduced in this age group.
"All participants underwent 2 out of 2 or 3 potential study conditions, in a randomised order, two period crossover design. The three potential study conditions were 3 weekend nights (Friday night to Monday morning) of: (A) 10h time in bed (TIB) each night, (B) 6h TIB each night or (C) 10h TIB with SWS suppression by acoustic stimuli (10h↓SWS) each night-Figure 1. Those aged ≤35 years (group 1) could be randomised to any 2 of the 3 conditions. Those >35 years (group 2) could only be randomised to Condition A (6h TIB) or Condition B (10h TIB). Men >35 years were not randomised to Condition C (10h↓SWS) because SWS is already reduced in this age group. Two separate randomisation lists for young and older men were computer-generated in blocks of 4. There was a minimum of 3 weeks wash-out between each study visit" (Killick. 2015).
The time of lights out was calculated by the subjects' individual screening actigraphy. Subjects were only told of their lights-off time immediately prior to bed on the first evening.
What if you can't sleep for 10h? The average effective sleeping time in the study was "only" ~9h. Since the subjects were instructed to stay in bed for a total of 10h they did however at least rest for 10h. It can thus be expected that you can achieve similar results if you "try your best" to sleep as long as possible and rest for the remaining hours. That being said without sleeping in a pitch black room and/or with blindfolds and earplugs only teenagers and adult drunkards will be able to effectively SLEEP for 10h, I suppose.
They were instructed that if they woke prior to lights on, they should remain in bed attempting further sleep until the lights were switched on.
Figure 1: Overview of the study design from the original publication (Killick. 2015).
The parameters the scientists investigated (a) the main outcome, insulin sensitivity that was measured in the morning following the 3rd intervention night by minimal modelling of 19 samples collected during a 2 hour oral glucose tolerance test, as well as (b) auxiliary outcomes, namely glucose, insulin, c-peptide, leptin, peptide YY, ghrelin, cortisol, testosterone and luteinising hormone (LH) which were measured in the fasted state on a daily basis.
Figure 2: Insulin sensitivity, glucose uptake, glucose & insulin AUC after meals (Killicks. 2015).
Much to my own surprise, the researchers found that 3 nights of catch up sleep lead to significant increases in insulin sensitivity compared to sustained sleep restriction. That's still not optimal, but the results clearly indicate that getting enough sleep on the weekend could ameliorate, but not abolish the detrimental effects of sleep restriction from Monday to Friday.

This conclusion is supported by the changes of the previously mentioned auxiliary variables: Fasting insulin, c-peptide, HOMA-IR, HOMA-β, leptin and PYY all decreased with ‘catch-up’ sleep, while the marker of insulin sensitivity QUICKI and the proanabolic male hormone testosterone increased. The attempt to decreases slow-wave-sleep via acoustic stimuli, on the other hand did not have significant effect on the insulin sensitivity of the subject.
Figure 3: The ill effects of sub-chronic (=days of) sleep restriction are undebatable. The increase in fasting insulin, HOMA-IR and QUICKI insulin sensitivity in the fasted state can however be ameliorated if you manage to get enough sleep on the weekend or the days after party nights / nights at the office, clinic or the lab (Killicks. 2015).
Bottom line: While the study at hand demonstrates that "catch up sleep", i.e. sleeping longer (10h) on the weekends in order to compensate for a lack of sleep (6h) reduces the impact of sleep reduction on insulin sensitivity, two things should be noted: (A) An amelioration is not a negation. In other words: Just because you get more than enough sleep on the weekend you will not avoid the negative impact of sleeping only 6h instead of the recommended 7-8h everyday. (B) A closer look at the data does yet also reveal that in the short runhealthy individuals are still able to keep their postprandial glucose levels (Figure 3, left / bottom) steady even if they don't get enough sleep.

Practically speaking, we can thus conclude: (1) An extended night of quality sleep may ameliorate the negative effects of the last party nights; (2) the acute effects of sleep restrictions won't turn you into a type II diabetic; (3) the chronic effects of sleep restriction should still not be underrated | Comment on Facebook!
References:

  • Killick, Roo, et al. "Metabolic and hormonal effects of ‘catch‐up’sleep in men with chronic, repetitive, lifestyle‐driven sleep restriction." Clinical Endocrinology (2015).