To develop and validate a frailty index (FI) that covers multiple domains, using routine hospital data. To investigate the FI’s validity, after excluding medication‐related items (FI‐ExMeds), for studies of frailty and polypharmacy.
A FI was derived from routine NSW hospital data following standard published guidance. In a development cohort (151 inpatients ≥ 70 years), the FI was correlated with the Reported Edmonton Frail Scale (REFS) using Pearson’s R. Validity and distribution of FI and FI‐ExMeds, and correlation with each other, were evaluated in a validation cohort (999 inpatients ≥ 75 years).
The mean FI for the development cohort was 0.27 (SD 0.09). The FI showed moderate linear correlation with the REFS (n = 148, R = 0.52, P < .001). In the validation cohort, mean FI (n = 993) and FI‐ExMeds (n = 990) were both 0.28 (SD 0.11). FI‐ExMeds showed high linear correlation with the FI (n = 990, R = 0.99, P < .001).
This multi‐domain FI is comparable to REFS, with adequate redundancy to exclude deficits for specific analyses.