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Background:Syndemics comprises the interaction of two or more biological diseases in different socio-cultural situations and in the context of varying healthcare standards that exacerbates their deleterious effects on the health of individuals, communities, and societies (1). There is increasing interest in using syndemics in the study of RMDs.Objectives:To identify quantitative and qualitative RMDs studies focused on syndemics through a systematic review and synthesize the available evidence.Methods:Inclusion criteria were using a syndemic framework in methods in RMDs studies. A systematic search of studies published from 2003 up to January 2021 was conducted in two electronic databases (SCOPUS and Web of Science). The systematic search was implemented (Figure 1): 1) the word syndemic(s) was searched using the advanced query string search, in the title, abstract, keywords, and text, to identify the relevant studies; 2) the publications were screened by three peer review groups; 3) the group evaluated each title and abstract and reviewed full-text articles to identify those relevant for review; 4) synthesis focused on identifying the variables of each study and integrating findings.Results:The initial search yielded 658 unique articles, from which ten studies were identified as syndemics in RMDs. After full-text review, six studies were excluded due to not inclusion of a syndemic framework. Four studies were included (Figure 1). The first quantitative study was on eight Latin-American (LatAm) indigenous communities (n=6,155). RMD´s were highly prevalent in the indigenous people (34.5%), RA prevalence was 2.4% in the Qom group of Argentina, and low back pain (LBP) being the most prevalent RMD (13.3%). RMDs were strongly associated with other comorbidities, unhealthy habits, low education levels, rural areas, socioeconomic conditions, and health inequality. The network analysis was the analytical approach using the Syndemic and Syndemogenesis Elements Modeler (SSEM). The second quantitative study focused on six urban/rural LatAm countries (n=55,724). LBP was significantly associated with comorbidities, unhealthy habits, low educational level, rural areas, and indigenous status. SSEM and cluster analysis showed a significant association between LBP prevalence and social variables. One qualitative study in fisher rural families (n=7) with three fisher rural generations from the Netherlands. A case study using life course theory. The first two generation reported syndemic vulnerability (psychological distress, cardiometabolic conditions, or musculoskeletal pain), and the third generation report less syndemic vulnerability, including musculoskeletal pain. A mixed study was identified focused on osteoarthritis with multimorbidities (cardiovascular, hypertension, diabetes mellitus) in an African American population (n=110) in the USA. The methodology was a descriptive secondary analysis and qualitative interviews. The study found that patients with hypertension (80.9%) reported greater chronic pain than those without. The lack of education added to the incorrect use of nonsteroidal anti-inflammatory drugs might contribute to the worst outcomes in this population, a significant burden of cardiovascular disease.Conclusion:There is growing interest and urge for integrating syndemics in the study of RMDs. This review has demonstrated that there are only a few publications to date. The statistical power and the analytical approach (SSEM-Syndemic and Syndemogenesis Elements Modeler) in the two quantitative studies are relevant. The qualitative study demonstrated less syndemic vulnerability with better health conditions linked to better socioeconomic advantages. The mixed qualitative study did not show a syndemic framework. It is necessary to carry out studies in RMDs from the syndemic perspective to document the complexity of the clinical and social determinants related to these diseases.References:[1]Singer M, Bulled N, Ostrach B, et al. Syndemics and the biosocial conception of health. The Lancet 2017;389:941–50.Disclosure of Interests:None declared

Introduction Midlife physical capability (PC) is associated with developmental factors in the populations of economically developed countries. As far as we know, there is no information for rural populations of low- and middle-income countries. The aim of the study was to investigate the influence of pre- and postnatal factors on midlife objective measures of PC in a 1966–67 birth cohort from a Mexican rural community. The hypothesis was that adverse developmental conditions are associated with low midlife PC. Methods In 1966–67, a birth cohort of all children from a poor Mexican rural community was assembled. Data on family socioeconomic status (SES), parental health and nutritional status, birth weight, postnatal growth and feeding patterns were registered. In 2018, out of the 336 cohort members, 118 were living in the community, and eighty-two of them underwent a comprehensive clinical evaluation. The evaluation included grip strength, gait velocity and chair-stand PC tests. In multivariable linear models, PC tests were the dependent variables, and prenatal, birth and postnatal factors were the independent variables. Adjustment for confounding was made with adult anthropometric, body composition, clinical and ageing status variables. Results Independent of adult health status and other ageing indicators, lower PC was associated with family organization and SES, parental nutritional status, birth weight, infant postnatal growth velocity, and weaning time. These results indicate that adverse family and environmental conditions that are prevalent in poor rural communities are associated with low midlife PC.

Adverse conditions in early life, including environmental, biological and social influences, are risk factors for ill-health during aging and the onset of age-related disorders. In this context, the recent field of social epigenetics offers a valuable method for establishing the relationships among them However, current clinical studies on environmental changes and lifespan disorders are limited. In this sense, the Tlaltizapan (Mexico) cohort, who 52 years ago was exposed to infant malnutrition, low income and poor hygiene conditions, represents a vital source for exploring such factors. Therefore, in the present study, 52 years later, we aimed to explore differences in clinical/biochemical/anthropometric and epigenetic (DNA methylation) variables between individuals from such a cohort, in comparison with an urban-raised sample. Interestingly, only cholesterol levels showed significant differences between the cohorts. On the other hand, individuals from the Tlaltizapan cohort with more years of schooling had a lower epigenetic age in the Horvath (p-value = 0.0225) and PhenoAge (p-value = 0.0353) clocks, compared to those with lower-level schooling. Our analysis indicates 12 differentially methylated sites associated with the PI3-Akt signaling pathway and galactose metabolism in individuals with different durations of schooling. In conclusion, our results suggest that longer durations of schooling could promote DNA methylation changes that may reduce epigenetic age; nevertheless, further studies are needed.