Measurement of organ structure and function enhances understanding of the physiological basis of frailty: The Cardiovascular Health Study

OBJECTIVES: To determine whether disease burden is associated with frailty independent of diagnosed chronic disease and whether physiological measurements provide greater understanding of the etiology of frailty. DESIGN: Cross-sectional. SETTING: Community. PARTICIPANTS: Two thousand four hundred thirty-seven participants in the Cardiovascular Health Study, 1992/93 examination (mean age 74.8 ± 4.8,43.4% male, 95.8% white). MEASUREMENTS: Disease burden and frailty were tabulated using 10-point scales (0 = healthy, 10 = unhealthy). Disease burden was the sum of measurements characterizing the vasculature, brain, kidneys, lungs, and glucose metabolism. Frailty was assessed using the frailty index reported by Fried. Multivariate linear models were used to determine the association between disease burden (predictor) and frailty (outcome). RESULTS: Unadjusted, 1-point-higher disease burden was associated with a 0.28-point-higher frailty score (P<.001). White matter grade, forced vital capacity, and cystatin-C were particularly strongly and significantly associated with frailty. Disease burden attenuated the association between frailty and age by 29%, and disease burden and age had similar associations with frailty. Disease burden attenuated the association between frailty and fibrinogen, Factor VIII, and C-reactive protein by 32%, 56%, and 83%, respectively. Frailty was associated with diagnosed depression, stroke, cognitive impairment, arthritis, and pulmonary disease but not coronary heart disease, diabetes mellitus, or kidney disease in the presence of a summary of disease burden. In the adjusted model, disease burden remained significantly associated with frailty (β5 0.11, P<.001). CONCLUSION: Disease burden was independently and significantly associated with frailty. These results emphasize that typically unrecognized physiological changes may contribute significantly to frailty.