In a large, nationally representative sample of elderly patients hospitalized with heart failure in the United States, nearly 1 in 6 had a secondary diagnosis of mental illness. Patients with a mental illness diagnosis received poorer to comparable quality of care, were more likely to be readmitted within the year following discharge, and had an increased mortality risk. Our findings identify areas of concern in the treatment and outcomes of patients with heart failure and mental illness.
The quality of medical care for patients with mental illness diagnoses presents a mixed picture, with no significant differences in ACE inhibitor prescription but less frequent left ventricular systolic function evaluation. All patients in the study cohort had Medicare insurance and, by being hospitalized, had demonstrated access to the health care system, thus diminishing the explanatory role of these factors. Physicians may be referring patients with mental illness for LVEF assessment at a lower rate than those without mental illness. Possible reasons for lower referral rates may range from less aggressive management of heart failure in patients with mental illness to a more insidious bias arising from the stigma associated with mental illness.28
It is also possible that patients with mental illness may be unable or unwilling to undergo LVEF assessment.
Consistent with the results of previous studies,9,10,13,15
we identified a notably higher risk of all-cause readmission among patients with mental illness, as well as increased risks of readmission for heart failure, even after adjustment for a variety of comorbid conditions. There are several possible mechanisms underlying the increased risk of readmission for heart failure among patients with mental illness. Patients with mental illness may be less adherent to treatment recommendations, including medication and rehabilitation regimens, thereby increasing their likelihood of readmission.29,30
Differences in heart failure symptom recognition may result in patients with mental illness deferring care until initial problems are sufficiently advanced that hospitalization is required. Mental illness may also cause patients with heart failure to underestimate their functional status, particularly for patients with depressive symptoms,31
thereby precipitating readmission when it may not be clinically necessary. Patients with mental illness were disproportionately women and admitted from residential facilities, characteristics associated with lower levels of social support.8
Poor social support after hospital discharge may diminish mentally ill patients’ abilities to cope with heart failure and thereby predispose them to readmission. Mental illness may also be a proxy for other unmeasured characteristics, including lower socioeconomic status and greater functional impairment, which are also associated with high rates of heart failure readmission.32
However, without detailed information concerning the quality of processes of care after discharge, it is unclear whether mental illness is independently associated with readmission or reflects poorer quality of care after discharge.
Heart failure readmission and mental illness readmissions may arise from a synergy of common processes underlying exacerbations of both conditions. For example, sympathetic nervous system activation has been observed in patients with depression.33
Augmentation of the sympathetic nervous system is also associated with the pathogenesis of heart failure and decompensation among patients with heart failure.34
Therefore, enhanced sympathetic nervous system activity in patients with heart failure may act to worsen depression and vice versa, thereby producing deterioration in both disease conditions.
Our findings of an increased risk of mortality associated with mental illness in patients with heart failure are consistent with previous reports of increased harm.2,6–9,11–15
Some of the same mechanisms, which may account for higher rates of readmission in patients with mental illness and heart failure, likely also contribute to higher mortality, including poorer adherence after discharge and poorer access to follow-up care. Neurohumoral alterations and autonomic dysfunction associated with mental illness may also serve as more proximal antecedents of excess mortality,35
particularly for patients with heart failure.36
However, the magnitude of the mental illness–associated adjusted 1-year mortality risk (OR, 1.20) is notably lower than previously published estimates of the mortality risk conferred by mental illness in patients with heart failure.6–9,13–15
The attenuated mortality hazard associated with mental illness observed in our cohort is similar to that reported in a previous study of the effect of a mental illness diagnosis on elderly patients with myocardial infarction.18
Studies finding higher mortality rates typically used diagnostic interviews rather than physician diagnoses to identify mental disorders,6–9,13–15
which may identify persons with more acute symptoms or those who are untreated. The advanced age common to both studies suggests that the decreased mortality risk may reflect survivorship bias whereby patients with mental illness who survive to older age represent a healthier cohort than patients without mental illness in ways that are unmeasured in this study. Concerns of such selection bias are heightened by the shorter life expectancies associated with most mental illnesses.37
The NHF Project constitutes the largest national, contemporary evaluation of elderly patients hospitalized with heart failure. The use of quality-of-care indicators and detailed clinical data represents significant methodological improvements on prior assessments of heart failure treatment patterns. However, our study has certain limitations that merit consideration. Administrative data produced from a single hospital encounter may not adequately identify all patients with mental illness.38
We sought to limit this effect by also evaluating administrative data for the full year preceding hospitalization. Nevertheless, mental illness remains markedly underdiagnosed by physicians in the community and the hospital setting.39
As such, our findings should not be seen as an estimate of the true prevalence of mental illness in elderly patients with heart failure but rather as an assessment of physician-recognized mental illness and its effects on patient treatment.
We restricted our analysis to Medicare patients 66 years and older who were hospitalized with heart failure; therefore, our findings may not be applicable to patients younger than 66 years or those not enrolled in fee-for-service Medicare. However, more than 80% of heart failure patients in the United States are 65 years or older40
(although this proportion may be smaller for patients with mental illness, who have an earlier median age of heart failure onset), and patients enrolled in Medicare managed care constitute less than 15% of Medicare beneficiaries,41
suggesting that both exclusions may result in only a minor loss in study generalizability. Our findings may not be applicable to patients who are not hospitalized or to practice patterns in the ambulatory setting. However, acute exacerbations of heart failure requiring hospitalization are common, particularly among elderly patients.42