Development and preliminary validation of a cognitive-physical frailty index in an older adult cohort: The NEDICES study

Background: Frailty is a multidimensional syndrome characterised by reduced physiological reserve and increased vulnerability to adverse health outcomes. While traditional frailty models focus primarily on physical decline, emerging evidence supports the integration of cognitive domains for a more comprehensive assessment. Objective: To develop and preliminarily validate a cognitive-physical frailty index using data from a large, prospective population-based cohort of older adults in central Spain. Methods: We constructed a frailty index based on 12 variables spanning physical, cognitive, subjective, and functional domains. These were selected from the Neurological Disorders in Central Spain (NEDICES) study using criteria based on feasibility, clinical relevance, and prior evidence of mortality prediction. Frailty distributions and transitions were analysed between two time points (1994–1995 and 1997–1998), and mortality risk was assessed using Cox proportional hazards models. Results: Among the 5,278 participants, the frailty distribution shifted to the right over the 3-year follow-up period, reflecting an increasing vulnerability.. The frailty index demonstrated a strong association with all-cause mortality (hazard ratio = 28.05; 95% CI: 16.37–48.06). Quartile-based stratification illustrated clearly within-sample progression. The index showed high goodness-of-fit under a gamma distribution, supporting its internal coherence. Conclusion: This brief, multidimensional frailty index offers a feasible tool for capturing early cognitive and physical decline and predicting short-term mortality in ageing populations. Although preliminary, these findings underscore the value of integrating cognitive indicators into frailty assessment. Future validation in other cohorts and with long-term data is warranted.