Translation, Cross-Cultural Adaptation, and Validation of the Croatian Version of the SARC-F Questionnaire for Assessing Sarcopenia in Older Adults

<b>Background/Objectives:</b> Sarcopenia is a growing public health challenge in older adults, being associated with functional decline, frailty, and increased mortality. The SARC-F questionnaire is a widely recommended screening tool for sarcopenia; however, no validated Croatian version has been available so far. This study aimed to translate, culturally adapt, and validate the Croatian version of the SARC-F questionnaire for older adults. <b>Methods:</b> In a cross-sectional design, 153 participants aged ≥ 65 years from Zagreb and Bjelovar were enrolled between March and September 2025. Psychometric evaluation included internal consistency (Cronbach's α), test-retest reliability (intraclass correlation coefficient, ICC), item-total correlations, and split-half reliability. Convergent validity was assessed via correlations with handgrip strength (HGS), Short Physical Performance Battery (SPPB), and timed up-and-go (TUG) tests. Known groups and construct validity were also examined. <b>Results:</b> The Croatian SARC-F showed good internal consistency (Cronbach's α = 0.76; 95% CI: 0.70-0.82), with item-total correlations ranging from 0.34 (falls) to 0.80 (stairs) and excellent test-retest reliability (ICC = 0.86). Strong correlations were found with SPPB (ρ = -0.50; <i>p</i> < 0.001), TUG (ρ = 0.50; <i>p</i> < 0.001), and handgrip strength (ρ = -0.42; <i>p</i> < 0.001), supporting convergent validity. An exploratory factor analysis indicated a unidimensional structure explaining 43% of the variance. <b>Conclusions:</b> The Croatian version of SARC-F is a reliable, valid, and clinically feasible tool for identifying older adults who are at risk of sarcopenia. The results support its use in national screening and cross-cultural research across Europe.