Functional Age Predicted by Electronic Short Physical Performance Battery Can Detect Frailty Status in Older Adults

Purpose: The importance of evaluating frailty status of older adults in clinical practice has been gaining attention with cumulative evidence showing its relevance in clinical outcomes and decision-making. We aimed to develop and validate whether the functional age predicted by an electronic continuous short physical performance battery (eSPPB) could predict frailty status. Patients and Methods: We reviewed medical records of outpatients (N=834) of Asan Medical Center, aged 51-95 years. We used the eSPPB data of 717 patients as a development cohort, and that of 117 patients, who also underwent comprehensive geriatric assessments, as a validation cohort. Frailty index was calculated by counting deficits of 45 geriatric items including comorbidities, daily functions, mobility, mood, and cognition. For functional age, we used balance score (0-4), gait speed (m/s), and stand-up time (s) measured 5 times in the chair rise test. Results: From the development cohort, we established a functional age using the formula (83.61 - 1.98*[balance score] - 5.21*[gait speed] + 0.23*[stand-up time]), by multivariate linear regression analysis with chronological age as a dependent variable (R-2 = 0.233). In the validation cohort, the functional age positively correlated with frailty index (p < 0.001). C-statistics classifying frailty (defined as frailty index >= 0.25) was higher (p < 0.001) with functional age (0.912) than that with chronological age (0.637). A cut-off functional age of >= 77.2 years maximized Youden's J when screening for frailty, with sensitivity of 94.4% and specificity of 80.8%. Conclusion: A newly developed functional age predictor using eSPPB parameters can predict the frailty status as defined by the deficit accumulation method and may serve as a physical biomarker of human aging.