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Divides the number of health deficits present by the number assessed, the cumulative deficit model of frailty described by Rockwood and Mitnitski.
Cumulative deficit frailty index
Frailty index = deficits present / deficits assessed; commonly quoted bands are under 0.12 fit, 0.12-0.24 vulnerable and over 0.24 frail
Educational estimate only. Not a substitute for professional clinical judgement, and must not be used to make treatment or dosing decisions.
At least 30 to 40 items give a stable index; the exact list matters less than the count and breadth.
Empirically the index rarely exceeds about 0.7, a submaximal limit seen across many populations.