BackgroundEarly research on the impact of the COVID-19 pandemic found persistent related anxiety in the general population. We hypothesised that this anxiety will be associated with increased pain in chronic pain patients diagnosed with fibromyalgia (FM).MethodsTo study this, we carried out a 10-day online survey with 58 female participants, diagnosed with FM and no other pain condition. We identified which aspects of the COVID-19 pandemic evoked anxiety. We then asked participants to provide daily ratings of both anxiety and pain on 101-point visual analogue scales (VAS). Key participant characteristics were included as mediators in a mixed-effects analysis, where the primary outcome was pain VAS.ResultsWe found that participants were most often anxious about “impact on relationships”, “a family member contracting COVID-19”, and “financial hardships”, but on average rated “financial hardship”, “access to medication”, and “home loss/eviction” as evoking the strongest anxiety. Mixed-effects modelling showed that an increase in pain was significantly associated with an increase in anxiety, when taking into account individual variance and daily caffeine intake. Age and intake of some mild analgesics were also linked to stronger pain.ConclusionOur results extend the initial findings from the literature about the effects of COVID-19 pandemic on chronic pain sufferers. We found that not only is pandemic anxiety in FM patients present, but it is associated with amplified self-assessed chronic pain.SignificanceThe long-term support of fibromyalgia patients is challenging for healthcare professionals due to the nature of the condition. The new normal introduced by the pandemic particularly hinders pain management, which is the leading request from this patient group. Our study demonstrates that mental health decline during the COVID-19 pandemic is directly related to the worsening of pain in fibromyalgia. Core stressors that evoke the strongest anxiety were identified thus providing guidance for where to focus patient support.

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Background: Anxiety, evoked by continuous inspiration of a 5 – 8% CO2 mixture, has been found to have an analgesic effect on self-reported pain. The precise mechanism whereby this effect obtains remains unknown. Methods: The present study tested whether temporal summation, the psychological counterpart of wind-up, is involved in hypercapnic analgesia. 21 healthy participants received painful transcutaneous electrical stimuli of varied intensity, during continuous inhalation of 7.5% CO2 mixture and medical air, presented in a single-blinded counterbalanced order. Continuous pain ratings were acquired to measure the temporal development of the pain response. Several points and events of interest that characterise the pain response profile were extracted from the continuous data. Results: Mixed-effects modelling demonstrated a reduction of all pain measures during inspiration of the anxiogenic mixture, but not air. This was accompanied by an increase in the psychological and physiological measures of anxiety. Analyses of the characteristic measures of temporal summation suggested that the hypercapnic mixture has an analgesic property evident from the start of the pain response. The same was true for the remainder of the response, the adaptation period, where pain ratings were also inhibited. The reduced pain ratings persisted during the remainder of the response. Anxiety was found to be a mediating factor for summative pain ratings but not the temporally sensitive TS measures, suggesting an overall, cumulative effect. Conclusions: The findings provide an explanation for the previously observed low self-reported pain during the inhalation of an anxiogenic hypercapnic mixture.

Illusory body resizing typically uses multisensory integration to change the perceived size of a body part. Previous studies associate such multisensory body illusions with frontal theta oscillations and parietal gamma oscillations for dis-integration and integration of multisensory signals, respectively. However, recent studies support illusory changes of embodiment from visual-only stimuli. Multisensory resizing illusions can also reduce chronic pain, potentially through modulation of cortical body representations. This preregistered study (N=48) investigated differences between multisensory visuo-tactile and uni-modal visual resizing illusions using EEG. We hypothesised (1) stronger illusion in multisensory compared to uni-modal, and uni-modal compared to asynchronous (dis-integration) conditions, (2) greater parietal gamma during multisensory compared to uni-modal, and (3) greater frontal theta during asynchronous compared to baseline conditions. Results partially supported EEG hypotheses, finding increased parietal gamma activity comparing multisensory to unimodal visual conditions, whilst finding increased parietal theta activity when comparing asynchronous to non-illusion conditions. While results demonstrated that only 27% of participants experienced the illusion with visual-only stimuli, further analysis suggested that those who experience visual-only illusions exhibit a different neural signature to those who do not. Our results support the importance of multisensory integration for illusory changes in perceived body size. However, we also suggest that visual-only illusions can influence cortical body representations for a significant proportion of participants, which may have implications for the development of accessible visual-only chronic pain treatments.