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In the second index, REM fragmentation decreased more in the SRT group than the control group, but in other indexes, there was not a statistical difference.
A new secondary data analysis from the MARTINI trial examined whether sleep restriction therapy (SRT) reduces rapid eye movement (REM) fragmentation, which is hypothesized to be a feature of insomnia. It was a parallel, randomized, controlled evaluation of SRT versus time-in-bed regulation (TBR).
“To our knowledge, this is the first study to examine whether SRT reduces REM sleep fragmentation, a proposed sleep characteristic of insomnia, in comparison to a matched control group,” the investigators wrote.1
The study led by Leonie Franziska Maurer, PhD, of the Nuffield department of clinical neurosciences at the University of Oxford, ultimately did not receive significant results to support a link that SRT reduces REM.
The participants (n = 56) were split into 2 groups, SRT (n = 27) and TBR (n = 29), and received treatment for 4 weeks. There were 36 females, and the mean age was 40.78 ± 9.08 years. For both groups, participants were prescribed a sleep window that was the same as their average self-reported total sleep time for the previous 2 weeks. Ambulatory polysomnographic recordings were performed at baseline, week 1, and week 4.
A portable polysomnography (PSG) system, SOMO HD™ recorded sleep at a participant’s home, and there were 6 scalp electrodes; 1 ground electrode; 1 scalp reference electrode; and 2 reference electrodes placed on each mastoid process.
“In the absence of a standard REM sleep fragmentation index, multiple indices were considered,” the team wrote. “We did not find clear evidence of a treatment effect of SRT on REM sleep fragmentation, with a statistically significant reduction being observed for just one of the three REM indices at one time point.”
Previous research found that individuals with insomnia experience more micro-arousals and awakenings during REM sleep, which was why the investigators added micro-arousals and awakenings in the indexes.2
The primary index included rapid eye movement arousals, awakenings, intrusions, and movement duration in hours through linear-mixed models that were fitted to access between-group differences. The study found there was no significant group difference for the rapid eye movement fragmentation index at week 1 (P = .009, d = .31) or week 4 (P = .741).1
Although in the second index—rapid eye movement sleep arousals, awakenings, and duration in hours—the investigators found that REM fragmentation decreased more in the SRT group than the control group at week 1 (P = .023, d = .46) but this was not the same case in week 4.
With the third index, which looked at REM arousals and duration in hours, investigators found a medium-sized effect at week 1 (d = .39), which supported SRT, but there was not a statistical significance (P = .051). At week 4, no effect was found (P = .908, d = .02).
At index 4, investigators found no group effects at week 1 (P = .395, d = .11) or week 4 (P = .153, d = .30).
“The absence of group effects at week 4 suggests that any treatment effect due to SRT may be of a temporary nature and potentially driven by mild sleep deprivation and/or reductions in pre-sleep arousal, both of which were prominent during early treatment,” the investigators wrote.
While the MARTINI trial did not prove if SRT reduces REM fragmentation, the research provides a basis for future studies.
“In summary, results from this exploratory analysis indicate that SRT may have potential to decrease REM sleep fragmentation, a proposed manifestation of hyperarousal, but only during the acute treatment phase,” the team concluded. “Future, purposely-designed studies are warranted to assess whether SRT reliably (and selectively) modifies REM fragmentation, and whether changes relate to clinical improvement in symptoms and/or overnight emotion processing.”