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    • Study inclusion for the current trial required

    2018-11-05

    Study inclusion for the current trial required self-reported unrefreshed or disturbed sleep. Although sleep disturbances are a hallmark feature of CFS [1], only a proportion of the participants had poor sleep over the baseline week of the study, as measured by actigraphy. There are a few possible explanations for this. Firstly, symptoms often fluctuate in these patients, and while generally the participants in the study had poor sleep, some participants may have had better sleep during the baseline week. Secondly, while CFS patients often report the symptom of unrefreshed sleep [1], this poorly understood sleep complaint [33] may not be accurately measured by actigraphic variables. In fact, although not presented in the results, we did not find any association between the objective actigraphy variables and subjective sleep ratings at baseline, consistent with the well-documented dissociation between objective and subjective sleep measurements [34,35]. This raises the issue of how sleep is best assessed in CFS patients (for further discussion see [1]). Results from the correlation analysis for both responders and the whole group revealed that higher Lactobacillus viable counts were significantly associated with poorer overall mood, including higher levels of confusion, depression and anger. In responders, lower Streptococcus viable count at the end of the trial was associated with better subjective sleep quality and vigor ratings. These findings highlight that commensal intestinal organisms, if disturbed, have the ability to influence emotional responses and behavior [36]. While the Lactobacillus finding is not in line with previous studies reporting a AICAR in depressive and anxiety symptoms after probiotic treatment in both healthy [37] and CFS populations [15], the current findings do support the D-lactate hypothesis. Possible explanations for the discrepancy between this and previous studies may be differences in the specific strain of Lactobacillus, which may have more protective or pathogenic qualities [38], or an adverse interaction between increased Lactobacillus levels and other organisms in the large intestine. Most lactobacilli produce both L- and D- lactic acids. It is possible that the association shown between Lactobacillus and mood in our study may be influenced by interactions with other microbes, for example the combination of high levels of Lactobacillus and Streptococcus may be more detrimental to the host. Further to this, Rao et al. (2009) showed that supplementation with Lactobacillus also increased Bifidobacterium levels at post-testing, and this was associated with decreased anxiety in CFS patients. Thus, it is difficult to determine the direct influence of a specific microbe, given the complex and interactive nature of the gut ecosystem. The current pilot study was conducted as an open label trial, without a placebo group. Instead, with the study design including different phases (baseline, treatment and follow up), each patient essentially became their own control. The benefit of such a design is that it reduces the between-group variability in symptom severity that is commonly found between patients with CFS. However, this design is limited by individual fluctuations in CFS patients׳ symptoms, as well as changes or differences in diet and exercise within and between participants, which may independently alter the outcome measures. There is also the possibility of placebo effects on our subjective measures. Interestingly, placebo effects in the CFS population are low with psychological interventions, but can be higher with immune-based interventions [39]. Thus, while placebo effects would also be expected to be minimized by the use of objective sleep monitoring, it could be argued that patient expectations of improved sleep may in fact lead them to become more relaxed during sleep which would be expressed through actigraphy. As discussed above, actigraphic measures may not be able to detect differences between non-restorative and restorative sleep, and thus further studies using more sensitive measures of sleep disturbance, such as polysomnography, are needed.