Results
Baseline Participant Characteristics
The mean age of participants was 74 ± 3 years; 48% were men and 59% were white. Median HABC Battery score was 2.3 (IQR 1.9–2.6). Table I presents the baseline characteristics. Frailty was present in 17.5% (moderate 16.2% and severe 1.3%) of participants by Gill criteria. Frail participants were older (74 ± 3 vs 73 ± 3 years, P < .001), more frequently women (60.1% vs 50.4%, P < .001), and black (53% vs 38%, P < .001). Frailty status by the 2 indexes was concordant in 1882 (66.7%) participants. Age; measures of adiposity (body mass index and waist to thigh ratio) and inflammation (tumor necrosis factor-α, interleukin-6); systolic blood pressure; heart rate; baseline diabetes mellitus and CVD; and fasting glucose, serum resistin, and creatinine levels all correlated with HABC Battery score ( Table II ).
Frailty and Incident Heart Failure
During a median follow-up of 11.4 (7.1–11.7) years, 466 (15.9%) participants developed HF (17.7 per 1000 person-years) (Figure 1). Compared to non-frail participants, those classified frail by the Gill index were at higher risk for HF (HR 1.36, 95% CI 1.08–1.71 and HR 1.88, 95% CI 1.02–3.47, for moderate and severe frailty, respectively). HABC Battery score was linearly associated with HF risk (Figure 2). In univariate analysis, HABC Battery score was associated with HF risk (HR 1.40, 95% CI 1.28–1.53 per SD decrease in score); this association persisted after adjustment for HABC HF Risk Score (HR 1.24, 95% CI 1.13–1.36). HR did not vary importantly in analyses that excluded HF events recorded in the first year of follow-up (data not shown). Progressive adjustments for serum lipids, physical activity, serum resistin, TNF-α, IL-6, history of arrhythmias, and respiratory function (FEV1/FVC) did not attenuate the association ( Table III ). Frailty remained a significant predictor of HF after controlling for incident CHD as a time varying covariate and death as a competing event.
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Figure 1.
HABC Battery score and incident heart failure. Lower baseline HABC Battery score was associated with a higher risk for heart failure. Rates are shown per 1000 person-years.
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Figure 2.
HABC Battery score and heart failure risk Hazard ratio and 95% "floating absolute" confidence intervals per quintile Health ABC battery are shown. The size of the box is proportional to the inverse of the variance of hazard ratio. Model adjusted for age and gender. Note: The fifth category is the reference.
The association between HABC Battery score and incident HF was similar across subgroups defined by age, gender, race, prevalent CHD, diabetes mellitus, and left ventricular hypertrophy (Figure 3). HABC Battery score had better discrimination than Gill index for HF prediction (C = 0.527 vs 0.586 for Gill index and Health ABC Battery score, respectively) (Figure 4). The Health ABC HF Risk Score yielded a C-index of 0.657 (95% CI 0.646–0.668); addition of HABC Battery score improved the model (change in C index, 0.014; 95% CI 0.018–0.010). The addition of the HABC Battery score to the Health ABC risk predictors appropriately reclassified 8.3% of participants who developed HF over a 5-year follow-up period and 5.15 of participants who did not (net-reclassification-improvement 0.073, 95%CI 0.021–0.125; P = .006) ( Table IV ).
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Figure 3.
HABC Battery scores and heart failure risk in subgroups. Frailty was associated with higher heart failure risk in multiple subgroups studied. Note: The model is adjusted for age and gender and stratified for prevalent coronary heart disease. LVH, Left ventricular hypertrophy; T2D, type 2 diabetes mellitus.
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Figure 4.
Comparison of discrimination of HABC Battery scores and Gill index.