Background & Aims
There is growing interest in identifying objective markers that can shed light on chronic pain etiology and guide the development of intervention and prevention strategies. One marker of increasing investigation is peak alpha frequency (PAF). While increased acute pain sensitivity is associated reliably with lower PAF values, existing research suggests that the relationship between PAF and chronic pain is more variable. While emerging work has compared individuals with chronic pain to healthy controls, no previous studies have examined differences in PAF between diagnoses or across chronic pain subtypes. This inconsistency could be attributable to chronic pain groups typically being examined as homogenous populations, without consideration for potential diagnosis-specific differences.
Methods
We reanalyzed a dataset of resting state EEG previously used to demonstrate a lack of difference in PAF between individuals with chronic pain and healthy controls (May et al., 2021; Ta Dinh et al., 2019). In this new analysis, we separated patients by diagnosis before comparing global PAF across three subgroups: chronic widespread pain (n=30), chronic back pain (n=38), and healthy controls (n=87). We additionally controlled for three characteristics with potential influence on PAF values: age, sex, and depression scores. Another measure with a potential relationship to PAF is pain intensity: this could not be entered into the primary analysis as healthy controls did not have current pain scores. We instead ran an additional analysis in the patient subgroups to determine if pain intensity had a significant relationship with PAF, and whether this relationship survived the same correction for age, sex, and depression scores.
Results
We found that pain intensity was similar across the two patient groups. After controlling for age, sex, and depression scores, we found that individuals with widespread pain had significantly higher global average PAF values than those of people with chronic back pain [p=0.028, ?=0.25 Hz]. In the analysis of pain intensity in the patient subgroups, we found no significant relationship between pain intensity at time of EEG collection and PAF values.
Conclusions
These novel findings reveal diagnosis-specific differences in EEG recordings across individuals with chronic pain that are distinct from an effect of pain intensity. Our work suggests that PAF shifts are unlikely to be a general marker for chronic pain, and holds important implications for future work exploring this measure in the context of pain physiology.
References
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