Defining Multimorbidity in Older Patients Hospitalized with Medical Conditions

Background The term multimorbidity identifies high-risk, complex patients and is conventionally defined as >= 2 comorbidities. However, this labels almost all older patients as multimorbid, making this definition less useful for physicians, hospitals, and policymakers. Objective Develop new medical condition-specific multimorbidity definitions for patients admitted with acute myocardial infarction (AMI), heart failure (HF), and pneumonia patients. We developed three medical condition-specific multimorbidity definitions as the presence of single, double, or triple combinations of comorbidities - called Qualifying Comorbidity Sets (QCSs) - associated with at least doubling the risk of 30-day mortality for AMI and pneumonia, or one-and-a-half times for HF patients, compared to typical patients with these conditions. Design Cohort-based matching study Participants One hundred percent Medicare Fee-for-Service beneficiaries with inpatient admissions between 2016 and 2019 for AMI, HF, and pneumonia. Main Measures Thirty-day all-location mortality Key Results We defined multimorbidity as the presence of >= 1 QCS. The new definitions labeled fewer patients as multimorbid with a much higher risk of death compared to the conventional definition (>= 2 comorbidities). The proportions of patients labeled as multimorbid using the new definition versus the conventional definition were: for AMI 47% versus 87% (p value<0.0001), HF 53% versus 98% (p value<0.0001), and pneumonia 57% versus 91% (p value<0.0001). Thirty-day mortality was higher among patients with >= 1 QCS compared to >= 2 comorbidities: for AMI 15.0% versus 9.5% (p<0.0001), HF 9.9% versus 7.0% (p <0.0001), and pneumonia 18.4% versus 13.2% (p <0.0001). Conclusion The presence of >= 2 comorbidities identified almost all patients as multimorbid. In contrast, our new QCS-based definitions selected more specific combinations of comorbidities associated with substantial excess risk in older patients admitted for AMI, HF, and pneumonia. Thus, our new definitions offer a better approach to identifying multimorbid patients, allowing physicians, hospitals, and policymakers to more effectively use such information to consider focused interventions for these vulnerable patients.

Automated summary

The conventional definition of multimorbidity, which identifies patients with >= 2 comorbidities, labels almost all older patients as multimorbid, making it less useful. This study developed new medical condition-specific definitions, called Qualifying Comorbidity Sets (QCSs), for acute myocardial infarction (AMI), heart failure (HF), and pneumonia patients, which resulted in fewer patients being labeled as multimorbid but with a higher risk of death compared to the conventional definition.