Abstract
Introduction
Cognitive impairment (CI) is associated with worse prognosis in patients with heart failure, especially in the elderly; however, its incremental prognostic ability in pre-existing prognostic models has not been well elucidated. Moreover, although some tools have been proposed for evaluating cognitive function, their difference in prognostic prediction has not been explicitly compared.
Methods
A total of 352 heart failure patients aged ≥75 years admitted to three hospitals were evaluated for their cognitive function using the Mini-Mental State Examination (MMSE) and Mini-cog during index hospitalization. We diagnosed CI if MMSE and Mini-cog were ≤23 and ≤2, respectively. The primary endpoint was all-cause death.
Results
The median age of the entire cohort was 85 (IQR: 80–88) years, and 47.7% of the subjects were male. Based on the MMSE and Mini-cog, the CI was diagnosed in 167 (47.4%) and 159 (45.2%) patients, respectively. The two diagnostic tools showed poor to moderate agreement (Cohen's kappa coefficient: 0.37, 95% CI: 0.27–0.47). During the follow-up period of median 346 (IQR: 195–489) days, 53 patients (15.1%) died. Although the Kaplan-Meier analysis showed that CI diagnosed using Mini-cog (CI-MC) was associated with significantly higher mortality (P=0.001), this association was not significant for CI diagnosed using MMSE (CI-MMSE) (P=0.059). On multivariate Cox regression analysis, CI-MMSE and CI-MC were individually associated with worse prognosis in older heart failure patients even after adjustment for Meta-Analysis Global Group in Chronic Heart Failure (MAGGIC) risk model and log B-type natriuretic peptide levels (CI-MMSE, HR: 2.05 [95% CI: 1.16–3.61]; and CI-MC, HR: 2.57 [95% CI: 1.46–4.53]). The receiver operating characteristic curve analysis for Mini-cog showed significantly higher area under the curve (AUC) than that for MMSE (0.61 vs. 0.52, p=0.045). To test the incremental prognostic capability, models were constructed by individually adding each score to the MAGGIC risk model, and the net reclassification improvement (NRI) and integrated discrimination improvement (IDI) were evaluated. CI-MMSE did not show incremental prognostic predictability (NRI: 0.28, p=0.069; IDI: 0.01, p=0.090), whereas CI-MC (NRI: 0.45, p=0.001; IDI: 0.03, p=0.001) did. Adding CI-MC instead of CI-MMSE to the MAGGIC risk model showed significant reclassification improvement (NRI: 0.45, p=0.002, IDI: 0.02, p=0.041).
Conclusion
In older patients with heart failure, CI defined by Mini-Cog is superior in providing additive prognostic value than that defined by CI based on MMSE.
Acknowledgement/Funding
This study is partially funded by Japan Heart Foundation Research Grant and Novartis Research Grants.
The Study of Cognitive Function and Related Factors in Patients With Heart Failure