A syndemic framework assesses the multidimensionality of the interrelationships of diseases and their circumstances. This approach has given important insights into other nonrheumatic diseases.Objective: We aimed to assess the use of framework and corresponding methodology to document syndemics and its impact in rheumatic and musculoskeletal diseases (RMDs).Methods: Using a mixed-methods systematic review, studies using the syndemic framework approach for RMDs were identified and published from January 2003 to January 2021. The Joanna Briggs Institute, Cochrane Collaboration, and PRISMA guidelines were followed to search, retrieve, revise, and analyze.Results: A total of 658 potential articles were identified, but only 10 were initially eligible. After a full-text review, 4 were included. Following a full-text review, 2 quantitative, 1 qualitative, and 1 mixed-methods study were included. In the first, network analysis found that RMDs were associated with comorbidities, unhealthy habits, low educational level, living in rural areas, socioeconomic conditions, and health inequality in indigenous communities. In the second, SSEM and cluster analysis demonstrated an association between low back pain and factors, such as comorbidities and indigenous status, among others, in urban/rural communities. The qualitative study examined 3 fishing family generations and reported less syndemic vulnerability. The mixed-methods study focused on osteoarthritis with multimorbidities in African American population, where lack of education added to worsening outcomes.Conclusions: Even though the insights syndemic studies have given to other areas, its use in rheumatology is scarce. The complexity of the clinical and social determinants related to RMDs makes it necessary to conduct further studies from a syndemic perspective.

Background: Post-acute COVID-19 syndrome (PACS) is a multi-system disease comprising persistent symptomatology after the acute phase of infection. Long-term PACS effects significantly impact patient outcomes, but their incidence remains uncharacterized due to high heterogeneity between studies. Therefore, we aimed to summarize published data on PACS, characterizing the clinical presentation, prevalence, and modifiers of prevalence estimates. Method: In this systematic review and meta-analysis, we research MEDLINE for original studies published from January 1st, 2020, to January 31st, 2021, that reported proportions of PACS manifestations. Studies were eligible for inclusion if they included patients aged ≥18 years with confirmed COVID-19 by RT-PCR or antigen testing and a minimum follow-up of 21 days. The prevalence of individual manifestations across studies was pooled using random-effects meta-analysis. For evaluating determinants of heterogeneity, meta-regression analysis was performed. This study was registered in PROSPERO (CRD42019125025). Results: After screening 1,235 studies, we included 29 reports for analysis. Twenty-seven meta-analyses were performed, and 61 long-term manifestations were described. The pooled prevalence of PACS was 56% (95%CI 45-66%), with the most common manifestations being diminished health status, fatigue, asthenia, dyspnea, myalgias, hyposmia and dysgeusia. Most of the included studies presented high heterogeneity. After conducting the meta-regression analysis, we identified that age, gender, number of comorbidities, and reported symptoms significantly modify the prevalence estimation of PACS long-term manifestations. Conclusion: PACS is inconsistently reported between studies, and population characteristics influence the prevalence estimates due to high heterogeneity. A systematized approach for the study of PACS is needed to characterize its impact adequately.