Beyond Body Composition: Regional Variations in Physical Function and Sarcopenia Among Older Adults in San José, Costa Rica and Baltimore, United States

Background As life span increases globally, so does the risk of aging with chronic health conditions. Differences in life span and health span between Costa Rica, a middle-income country, and the United States, a high-income country, suggest cultural context may influence how age-related changes in muscle mass, body composition, and physical function affect older adults. This analysis compared body composition, physical function, and sarcopenia prevalence among aging adults from two major metropolitan cities: San José, Costa Rica and Baltimore, Maryland, US. Methods Baseline data from study participants at the Baltimore Veterans Affairs Medical Center were matched with publicly available baseline data from a similar cohort at Universidad de Costa Rica. All participants had assessments of body composition (dual energy x-ray absorptiometry), physical function (handgrip strength, Six Minute Walk Test [6MWT]), and general health characteristics (vitals, comorbidities). Sarcopenia prevalence was defined using European Working Group on Sarcopenia in Older Persons criteria. Participants were age- and sex- matched between sites prior to analysis. Results Seventy-eight participants (San José n = 39; Baltimore n = 39) were included. Compared to participants from Baltimore, participants from San José had lower lean mass (54.97 ± 7.36 vs. 62.45 ± 6.91% bodyweight, p < 0.01) and higher fat mass (43.17 ± 7.78 vs. 33.95 ± 7.37% bodyweight, p < 0.01). Participants from San José also had lower grip strength (27.43 ± 8.48 vs. 32.54 ± 9.27 kg, p = 0.04) but greater 6MWT distance (486.18 ± 99.47 vs. 387.53 ± 102.95 m, p < 0.01) compared to those from Baltimore. Regional differences in grip strength were no longer significant after adjusting for body composition, though 6MWT differences remained significant after controlling for absolute (kg) and relative (% bodyweight) lean and fat mass. Sarcopenia prevalence was greater in San José based on appendicular lean mass/height ² (74.4% vs. 2.6%, p < 0.001) and grip strength (65.2% vs. 16.2%, p < 0.001) criteria. Conclusions Regional differences in muscle composition and physical function highlight the potential influence of cultural, cardiometabolic, and environmental factors beyond body composition alone. These findings underscore the importance of culturally and contextually tailored strategies to support physical function and mitigate sarcopenia risk in aging populations globally.