Theory 13/Geriatrics & Frailty
Frailty Is a Reserve Ratio
The claim
Frailty is set by the ratio of physiological reserve to accumulated load rather than by age or comorbidity count, so a younger patient with high load can be frailer than an older one with more reserve.
01The mechanism
A stressor requires reserve to compensate. Whether it produces a deficit depends on how much reserve remains relative to the demand, which is a ratio.
That makes reserve the unifying variable, and explains why comorbidity counts mispredict outcomes in both directions.
02What this is not
Age-and-comorbidity indices
Those count conditions. This measures reserve against load, which explains discordance with age.
03Predictions
- P1Outcomes should track the ratio better than comorbidity count.
- P2Reserve-building interventions should reduce frailty at constant comorbidity.
04Refutation
Outcomes tracking age or comorbidity at controlled ratio would favour the indices.