Two year follow-up of sleep diaries and polysomnography in CFS: a cohort study

[Dolphin]

http://www.tandfonline.com/doi/full/10.1080/21641846.2017.1297280

Two year follow-up of sleep diaries and polysomnography in chronic fatigue syndrome: a cohort study
Sean L. Davidson, Zoe M. Gotts, Jason G. Ellis & Julia L. Newton
Pages 1-11 | Received 30 Oct 2016, Accepted 16 Feb 2017, Published online: 02 Mar 2017

ABSTRACT
Background: Chronic fatigue syndrome (CFS) is a prevalent and debilitating symptom complex of unknown aetiology. Up to 96.8% of people with CFS report unrefreshing sleep and many describe, in qualitative interviews, changes in sleep over the course of their illness.

Purpose: To establish whether subjective and objective sleep parameters change over a two-year follow-up period in patients with CFS.

Methods: Twenty-two participants with CFS were recruited during routine consultations at a clinic in the North-East of England. All had their sleep characterised in a previously published cross-sectional study. Two were excluded from this analysis because they fulfilled criteria for a primary sleep disorder. The remaining 20 were contacted and 15 repeated fatigue- and sleep-quality questionnaires and sleep diaries, two years after their sleep was first characterised. Seven participants also repeated two consecutive nights of polysomnography. Paired statistical tests were used to compare follow-up with baseline measures.

Results: Subjective questionnaires and sleep dairies did not show differences over two years follow-up. However, polysomnography demonstrated a higher proportion of stage one sleep (P < .01) and more awakenings per hour (P = .04) at follow-up.

Conclusions: This study is the first to longitudinally assess sleep parameters in people with CFS. The results suggest that subjective perceptions of sleep remain stable, although objective measures indicated a tendency towards increased periods of lighter sleep. However, the small number of participants increases the likelihood that observed differences are Type I errors.

KEYWORDS: Chronic fatigue syndrome, myalgic encephalomyelitis, unrefreshing sleep, nonrestorative sleep, polysomnography, sleep diaries

• 
  

 

[Dolphin]

The number of minutes of N1, the transition stage between wakefulness and sleep, was increased at follow-up compared to baseline (P ≤ .01; Table 3). This difference was seen in every individual regardless of the total time in N1 or time in N1 as a percentage of TST was considered. Other than this increase in N1, no differences in sleep architecture variables were observed between original participation and follow-up subjects.

The difference was quite dramatic:

Time in N1 (mins)
Original mean (SD)a (N = 6) 14.3 (8.8)
Follow-up mean (SD)a (N = 6) 39.3 (16.6)
Mean difference (95% CI)b 25 (8.8)
Significance (P) .001e
ePaired samples t-test.

As opposed to the relative stability of our subjective measures over time, repeated PSG tests in six of the original participants found that the amount of N1 sleep and the number of awakenings per hour were increased at follow-up. Considered a transition phase between sleep and wakefulness, N1 is associated with some sensory processing of external stimuli and greater arousability [28] and thus might account for the increase in frequency of awakenings. The proportions of N2, N3 and REM were correspondingly decreased at follow-up though these changes were less significant. Although changes in the microarchitecture of N1 have previously been described in CFS [29], changes in the duration or proportion of N1 have not.

Four of the six participants who successfully completed the PSG protocol at follow-up were taking sleep-altering medications. Two were on SSRIs for many years which usually increases the proportion of N1 and N2 as well as the frequency of awakenings [30]. Despite no change in their SSRIs at follow-up, N1 and frequency of awakenings increased at follow-up in these two participants. Medications prescribed in the interval between baseline and follow-up included amitriptyline and melatonin (not usually associated with an increase in N1 [31,32]), and gabapentin which is supposed to decrease N1 [33]. Changes in medications do not seem to be an adequate explanation for the increase in N1 which was observed in all participants including two who remained free of any sleep-altering medications throughout.

Objectively defined disorders such as obstructive sleep apnoea and periodic limb movement disorder are associated with brief arousals resulting in fragmented sleep and an increased proportion of N1 [34,35]. However, the scoring of recordings in this study did not include micro-arousals which are increases in EEG frequency greater than 16 Hz, lasting three or more seconds, preceded by ≥10 seconds of stable sleep [24]. Three studies have demonstrated a greater number of micro-arousals in people with CFS as compared to controls even when, as in this study, people with objectively defined sleep disorders were screened for and excluded [11,15,36].

 

[Diwi9]

@Dolphin - Is there a full-text version, or can you find the mean Stage 1 sleep percentage for ME/CFS and post?

 

[Dolphin]

@Dolphin - Is there a full-text version, or can you find the mean Stage 1 sleep percentage for ME/CFS and post?

Percentage of N1 (of TST)
Original mean (SD)a (N = 6) 3.2 (2.2)
Follow-up mean (SD)a (N = 6) 8.6 (4.3)
Mean difference (95% CI)b 5.4 (2.3)
Significance (P) .003e
ePaired samples t-test.

TST: total sleep time

 

[Dolphin]

Awakening Index (NWAK per hour)
Original mean (SD)a (N = 6) 2.2 (1.17)
Follow-up mean (SD)a (N = 6) 2.6 (1.67)
Mean difference (95% CI)b 0.4 (0.6)
Significance (P) .037e
ePaired samples t-test.