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Prefrailty and sarcopenia in combination are more predictive of mortality than either condition alone. Early detection of these syndromes determines the prognosis of health-related adverse events since both conditions can be reversed through appropriate interventions. Nowadays, there is a lack of cheap, portable, rapid, and easy-to-use tools for detecting prefrailty and sarcopenia in combination. The aim of this study is to validate an iPhone App to detect prefrailty and sarcopenia syndromes in community-dwelling older adults. A diagnostic test accuracy study will include at least 400 participants aged 60 or over without cognitive impairment and physical disability recruited from elderly social centers of Murcia (Spain). Sit-to-stand muscle power measured through a slow-motion video analysis mobile application will be considered as the index test in combination with muscle mass (calf circumference or upper mid-arm circumference). Frailty syndrome (Fried’s Phenotype) and sarcopenia (EWGSOP2) will both be considered as reference standards. Sensibility, specificity, positive and negative predictive values and likelihood ratios will be calculated as well as the area under the curve of the receiver operating characteristic. This mobile application will add the benefit for screening large populations in short time periods within a field-based setting, where space and technology are often constrained (NCT05148351).

Objectives: To analyze the associations between the different operational definitions of sarcopenia published in the last decade and reduced muscle power with a set of adverse health-related outcomes, such as comorbidities, depression, polypharmacy, self-perceived health, educational attainment, socioeconomic status, falls, and hospitalizations in Spanish community-dwelling older adults. Methods: A total of 686 community-dwelling older adults (median age: 72; women: 59.2%; physically active: 84%) were included in this cross-sectional analysis (ClinicalTrials.gov: NCT05148351). Sarcopenia was assessed using the FNIH, EWGSOP2, AWGS, and SDOC algorithms. Reduced muscle power was defined as the lowest sex-specific tertile and measured during the rising phase of the sit-to-stand test using a validated mobile application. Unadjusted and adjusted logistic regressions by potential confounders were performed to identify the association between sarcopenia and reduced muscle power with health-related outcomes. Results: Sarcopenia prevalence was 3.4%, 3.8%, 12.4%, and 21.3% according to the SDOC, FNIH, EWGSOP2, and AWGS, respectively. Among these definitions, moderate and large associations with health-related outcomes were observed for EWGSOP2 and SDOC, respectively, but few associations were found for FNIH and AWGS criteria. Reduced muscle power was associated more frequently and moderately with health-related outcomes compared to sarcopenia definitions. These associations remained constant after adjusting for confounders. Conclusions: The prevalence and impact of sarcopenia varied depending on the definitions used. Among the sarcopenia definitions, the SDOC exhibited the strongest associations, while reduced muscle power was the variable most frequently associated with health-related outcomes compared to any of the four sarcopenia definitions in well-functioning and physically active community-dwelling older adults.

BACKGROUND Probable sarcopenia is determined by a reduction in muscle strength assessed with the handgrip strength test or 5 times sit-to-stand test, and it is confirmed with a reduction in muscle quantity determined by dual-energy X-ray absorptiometry or bioelectrical impedance analysis. However, these parameters are not implemented in clinical practice mainly due to a lack of equipment and time constraints. Nowadays, the technical innovations incorporated in most smartphone devices, such as high-speed video cameras, provide the opportunity to develop specific smartphone apps for measuring kinematic parameters related with sarcopenia during a simple sit-to-stand transition. OBJECTIVE We aimed to create and validate a sit-to-stand video analysis–based app for diagnosing sarcopenia in community-dwelling older adults and to analyze its construct validity with health-related risk factors and frailty. METHODS A total of 686 community-dwelling older adults (median age: 72 years; 59.2% [406/686] female) were recruited from elderly social centers. The index test was a sit-to-stand video analysis–based app using muscle power and calf circumference as proxies of muscle strength and muscle quantity, respectively. The reference standard was obtained by different combinations of muscle strength (handgrip strength or 5 times sit-to-stand test result) and muscle quantity (appendicular skeletal mass or skeletal muscle index) as recommended by the European Working Group on Sarcopenia in Older People-2 (EWGSOP2). Sensitivity, specificity, positive and negative predictive values, and area under the curve (AUC) of the receiver operating characteristic curve were calculated to determine the diagnostic accuracy of the app. Construct validity was evaluated using logistic regression to identify the risks associated with health-related outcomes and frailty (Fried phenotype) among those individuals who were classified as having sarcopenia by the index test. RESULTS Sarcopenia prevalence varied from 2% to 11% according to the different combinations proposed by the EWGSOP2 guideline. Sensitivity, specificity, and AUC were 70%-83.3%, 77%-94.9%, and 80.5%-87.1%, respectively, depending on the diagnostic criteria used. Likewise, positive and negative predictive values were 10.6%-43.6% and 92.2%-99.4%, respectively. These results proved that the app was reliable to rule out the disease. Moreover, those individuals who were diagnosed with sarcopenia according to the index test showed more odds of having health-related adverse outcomes and frailty compared to their respective counterparts, regardless of the definition proposed by the EWGSOP2. CONCLUSIONS The app showed good diagnostic performance for detecting sarcopenia in well-functioning Spanish community-dwelling older adults. Individuals with sarcopenia diagnosed by the app showed more odds of having health-related risk factors and frailty compared to their respective counterparts. These results highlight the potential use of this app in clinical settings. CLINICALTRIAL ClinicalTrials.gov NCT05148351; https://clinicaltrials.gov/study/NCT05148351 INTERNATIONAL REGISTERED REPORT RR2-10.3390/s22166010