Assessing working memory function in individuals with fibromyalgia: A systematic review and meta-analysis

Fibromyalgia is a condition characterized by wide-spread nonspecific pain. In conjunction with pain, individuals also commonly report experiencing a loss of mental clarity, more colloquially referred to as "fibro-fog". Fibro-fog is subjectively described as one of the most debilitating aspects of the condition, with subjective memory complaints being of high concern. Despite this, research has only recently begun to explore the effects of fibromyalgia in cognition more broadly. However, this research is limited by small samples and a focus on cognition as a broader construct. Thus, to further our understanding of the impact of fibromyalgia on objective memory performance a systematic review and meta-analysis was undertaken. The aim was to focus on working memory specifically, with reference to verbal and visual modalities. A comprehensive search of 6 databases was undertaken (CINAHL, PubMed, Embase, PsycINFO, Web of Science, Medline), which yielded 8358 papers. Following removal of duplicates and screening 29 studies were eligible for inclusion. Papers were eligible for inclusion if they contained an adult fibromyalgia and healthy control group and a standardized measure of working memory. Results of the Standard Quality Assessment Criteria for Evaluating Primary Research Papers from a Variety of Fields indicated that all included studies were of good-strong quality. Individuals with fibromyalgia showed significantly impaired verbal working memory performance when compared to healthy controls, with a moderate effect size (g = -0.66, CI = -0.94, -0.38). Alternatively, no significant differences were found for visual working memory performance. These findings suggest that modality specific memory impairments are present in individuals with fibromyalgia. Subgroup analyses also indicated that females showed impaired working memory performance in both domains (with small (g = -0.34, CI = -0.59, -0.10) to moderate effect sizes (g = -0.64, CI = -1.02, -0.27)). Further research exploring how these foundational deficits impact higher order cognition is warranted. These findings highlight the importance of considering nonphysical symptoms in the treatment and management of fibromyalgia.