Background 

Comorbidities are risk factors for poor clinical outcomes in patients with heart failure. However, no consensus has been reached on how to assess comorbidities related to clinical outcomes in patients with heart failure.

Objective 

The aims of this study were to review (1) how comorbidities have been assessed, (2) what chronic conditions have been identified as comorbidities and (3) the rationale for choosing the comorbidity instruments and/or specific comorbidities when exploring clinical outcomes in patients with heart failure.

Methods 

The clinical outcomes of interest were mortality, hospitalization, quality of life, and self-care. Three electronic databases and reference list searches were used in the search.

Results 

In this review, we included 39 articles using 3 different ways to assess comorbidities in the relationship with clinical outcomes: using an instrument (ie, Charlson Comorbidity Index), disease count, and including individual comorbidities. A total of 90 comorbidities were investigated in the 39 articles; however, definitions and labels for the diseases were inconsistent across the studies. More than half of the studies (n = 22) did not provide a rationale for selecting the comorbidity instruments and/or all of the specific comorbidities. Some of the rationale for choosing the instruments and/or specific comorbidities was inappropriate.

Conclusions 

We found several issues related to measuring comorbidities when examining clinical outcomes in patients with heart failure. Researchers need to consider these methodological issues when measuring comorbidities in patients with heart failure. Further efforts are needed to develop guidelines on how to choose proper measures for comorbidities.