Association of admission frailty and frailty changes during cardiac rehabilitation with 5-year outcomes

Abstract

Aims: Examine the association between (1) admission frailty and (2) frailty changes during cardiac rehabilitation (CR) with 5-year outcomes (i.e. time to mortality, first hospitalization, first emergency department (ED) visit, and number of hospitalizations, hospital days, and ED visits).

Methods and results: Data from patients admitted to a 12-week CR programme in Halifax, Nova Scotia, from May 2005 to April 2015 (n = 3371) were analysed. A 25-item frailty index (FI) estimated frailty levels at CR admission and completion. FI improvements were determined by calculating the difference between admission and discharge FI. CR data were linked to administrative health data to examine 5-year outcomes [due to all causes and cardiovascular diseases (CVDs)]. Cox regression, Fine-Gray models, and negative binomial hurdle models were used to determine the association between FI and outcomes. On average, patients were 61.9 (SD: 10.7) years old and 74% were male. Mean admission FI scores were 0.34 (SD: 0.13), which improved by 0.07 (SD: 0.09) by CR completion. Admission FI was associated with time to mortality [HRs/IRRs per 0.01 FI increase: all causes = 1.02(95% CI 1.01,1.04); CVD = 1.03(1.02,1.05)], hospitalization [all causes = 1.02(1.01,1.02); CVD = 1.02(1.01,1.02)], ED visit [all causes = 1.01(1.00,1.01)], and the number of hospitalizations [all causes = 1.02(95% CI 1.01,1.03); CVD = 1.02(1.00,1.04)], hospital days [all causes = 1.01(1.01,1.03)], and ED visits [all causes = 1.02(1.02,1.03)]. FI improvements during CR had a protective effect regarding time to all-cause hospitalization [0.99(0.98,0.99)] but were not associated with other outcomes.

Conclusion: Frailty status at CR admission was related to long-term adverse outcomes. Frailty improvements during CR were associated with delayed all-cause hospitalization, in which a larger effect was associated with a greater chance of improved outcome.

Keywords: Cardiac rehabilitation; Frailty; Hospitalization; Mortality.

Graphical Abstract

Figure 1

Flowchart of participants.

Figure 2

Mortality rates by (A) admission frailty index and (B) frailty index change. Improvement—frailty index decreased by at least 0.03; stable—frailty index changed by <0.03; worsened—frailty index increased by at least 0.03 during cardiac rehabilitation.

Figure 3

Total number of hospitalizations, hospital days, and emergency department visits by admission frailty index (panels A, C, and E) and by frailty index change categories (panels B, D, and F). Improvement—frailty index decreased by at least 0.03; stable—frailty index changed by <0.03; worsened—frailty index increased by at least 0.03 during cardiac rehabilitation. AC, all causes; CVD, cardiovascular disease.

Figure 4

Predicted hazard ratios for risk of mortality (panels A and B), hospitalization (panels C and D), and ED visit (panels E and F) by frailty index score at cardiac rehabilitation admission (panels A, C, and E) and improvement during cardiac rehabilitation (panels B, D, and F). Admission frailty index was a significant predictor of all-cause and cardiovascular disease risk of mortality, hospitalization, and emergency department visit (P < 0.001). Frailty index improvement was a significant predictor of all-cause risk of hospitalization (P = 0.016) but not for all other outcomes. Panels A, C, and E contains ‘rug’ plots which visualize the distribution of predicted hazard ratios and admission frailty index scores. The areas in panels B, D, and F x-axes indicate different levels of clinically important changes in frailty index score during cardiac rehabiliation: less than −0.03 = worsening, −0.03 to 0.03 = stable, and greater than 0.03 = improvement. Grey bands represent 95% confidence intervals. All models were adjusted for sex, age, referring diagnosis, education, employment, smoking status, marital status, and year of cardiac rehabilitation. The admission frailty index model was also adjusted for completion of cardiac rehabilitation status and the frailty index improvement model for admission frailty index score and per cent of exercise sessions attended. ED, emergency department.