Cumulative deficits better characterize susceptibility to death in elderly people than phenotypic frailty: lessons from the Cardiovascular Health Study

Abstract

Objectives: To compare how well frailty measures based on a phenotypic frailty approach proposed in the Cardiovascular Health Study (CHS) and a cumulative deficits approach predict mortality.

Design: Cohort study.

Setting: The main cohort of the CHS.

Participants: Four thousand seven hundred twenty-one individuals.

Measurements: A phenotypic frailty index (PFI) was defined in the same way as proposed in the CHS: assessing weight loss, exhaustion, low physical activity, slowness, and poor grip strength. A cumulative deficit index (DI) was defined based on 48 elderly deficits (signs, symptoms, impairments, diseases) included in the index, with equal weights.

Results: Of the 1,073 frailest individuals with the lowest survival, the PFI, categorized as proposed in the CHS into robust, prefrail, and frail categories, underestimated the risk of death for 720 persons, whereas the DI categorized into the same three frailty categories underestimated the mortality risk for 134 persons. The higher power of the DI for discriminating frail individuals in their susceptibility to death also followed from comparison of quasi-instantaneous values of both indices. The three-level DI identified 219 individuals as frail of 361 individuals identified as frail according to the three-level PFI.

Conclusion: The DI can more precisely evaluate chances of death because it assesses a broader spectrum of disorders than the PFI. Both indices appear to be frailty related. Integration of both approaches is highly promising for increasing the precision of discrimination of the risk of death and especially for identification of the most vulnerable elderly people.

Figures

Figure 1

Survival curves smoothed by Cox regression for each of the 9 selected sub-groups defined on the basis of categorization of the phenotypic frailty index (PFI) and deficit index (DI) into 3 categories (see Table 4) as robust, pre-frail, and frail: 1) PFI3robust and DI3robust; 2) PFI3robust and DI3pre-frail; 3) PFI3robust and DI3frail; 4) PFI3pre-frail and DI3robust; 5) PFI3pre-frail and DI3pre-frail; 6) PFI3pre-frail and DI3frail; 7) PFI3frail and DI3robust; 8) PFI3frail and DI3pre-frail; and 9) PFI3frail and DI3frail.