The Complexities of Multimorbidity and Improving Care Coordination

Amy Salls
By Amy Salls
Director, Population Health Strategy

Multimorbidity is the co-existence of at least two or more chronic conditions within one person and is commonly associated with the high utilization of healthcare resources and decreased quality of life. While the complexity of multimorbidity is a major challenge for population health, it is especially challenging for elderly populations where multimorbidity is common.

 Medicare Beneficiaries With Multimorbidity


When individuals are being treated for multiple chronic conditions, they are often seen by multiple providers and prescribed multiple medications. This leads to “increased risk of inappropriate drug use, under-use of effective treatments, medication errors, poor adherence, drug-drug and drug-disease interactions and — most importantly — adverse drug reactions.1

For this reason, focusing care coordination efforts on a cohort of multimorbid individuals with a multitude of providers may be an effective strategy for affecting population health. Traditionally this has been difficult to address. Fortunately, the Johns Hopkins ACG® System provides a method for assessing both comorbidity and the degree of patient sharing among physicians, expressed with a metric called Care Density. Higher care density, that is care rendered by providers who frequently share patients, is associated with lower overall utilization2 and improved outcomes3. The converse, care rendered by providers who infrequently share patients, may be used to identify a population for care coordination interventions.

care density morbidity infographic 

The above graphic is representative of an elderly population with each smaller, inner rectangle proportional to the population falling into various risk categories, as defined by the ACG System morbidity markers. The gray rectangle in the lower right corner of the graphic represents a population with a high degree of multimorbidity, plus a high number of providers that do not share patients. The healthcare cost difference between this population and populations of similar morbidity is over $19,000 per member per year (PMPY). This relatively small proportion of the population is using a disproportionate share of resources even in comparison to other individuals with multiple chronic conditions.

When managing scarce care management resources, this method of stratification identifies a small population with the greatest needs for care coordination and the greatest opportunities for hospitalization reduction and other cost savings. Risk stratification is a core competency required to effectively implement population health strategies. Viewing a population across multiple dimensions of care is enabled by the Johns Hopkins ACG System.

Improving care coordination is particularly important for a rapidly aging population challenged with multimorbidity. With the Care Density metric, health plans now have a new opportunity to master the complexity of multi-morbidity and manage population health more effectively while improving health outcomes and reducing cost.

For more information on Care Density, download our white paper Care Density: A New Way to View Care Coordination.


1 Alessandro Nobili, Silvio Garattini, Pier Mannuccio Mannucci; Multiple diseases and polypharmacy in the elderly: challenges for the internist of the third millennium; Journal of comorbidity; 2011;

2 Pollack CE1, Weissman GE, Lemke KW, Hussey PS, Weiner JP; Patient sharing among physicians and costs of care: a network analytic approach to care coordination using claims data; J Gen Intern Med; 2013 Mar;28(3):459-65. doi: 10.1007/s11606-012-2104-7. Epub 2012 Jun 14.

3 Pollack CE1, Lemke KW, Roberts E, Weiner JP; Patient sharing and quality of care: measuring outcomes of care coordination using claims data; Med Care. 2015 Apr;53(4):317-23. doi: 10.1097/MLR.0000000000000319.

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