Comparison of two frailty indices in the physicians' health study.

BACKGROUND

As the population ages it is important to identify frailty, a powerful predictor of morbidity and mortality, and often an important unmeasured confounder. We sought to develop a frailty index in the Physician's Health Study (PHS) and estimate the association with mortality.

METHODS

Prospective cohort study. Annual questionnaire assessed mood, function and health status. Two frailty scores were compared - cumulative deficit frailty index (PHS FI) and modified Study of Osteoporotic Fracture (mSOF) frailty score. Endpoints committee confirmed mortality.

RESULTS

12,180 male physicians ≥60 years were analyzed. Mean(SD) follow-up was 10(3) years, 2168 deaths occurred. PHS FI identified 4412 (36%) physicians robust, 5305 (44%) pre-frail, and 2463 (20%) frail, while mSOF identified 7323 (61%) robust, 3505 (29%) pre-frail and 1215 (10%) frail. Age-standardized rate of death was lower among subjects identified as robust using the PHS FI, 11/1000 person-years (PY) (95% Confidence Interval (CI): 9.5-11.9) compared to 14/1000PY (95% CI: 13.5-15.4) using mSOF [P-difference <0.001]. In the prefrail group, death rates were 16/1000PY in PHS FI and 21/1000PY in mSOF, [P-difference <0.001]. There was no difference in age-adjusted mortality rates in the frail group according to each definition (35 vs 33/1000PY). Survival analysis showed an increased risk of mortality in each frailty category using either definition, (log-rank p<0.001).

CONCLUSION

The PHS FI outperformed mSOF in identifying risk of death particularly in robust and pre-frail categories. Similar indices can be created in existing datasets to identify frail individuals and where appropriate account for frailty, an often unmeasured confounder.