BACKGROUND AND DEFINITIONS
Multimorbidity is often defined as the presence of two or more chronic co-occurring conditions. Although this is the formal definition, most clinicians consider multimorbidity to be particularly vexing when it involves a broad array of conditions and is also accompanied by functional limitations, cognitive impairment, or mental health concerns, as well as interactions between the conditions themselves and their treatments.
Among older adults, multimorbidity is the rule rather than the exception: almost half of those 65 to 69 years old have two or more chronic conditions; this proportion increases to 75% among those age 85 years or older. Thanks to public health interventions, technology, and overall population aging, the proportion of older adults with multimorbidity has grown significantly in the past decade. Among those age 65 years or older, the number of those with two or more conditions (from among nine measured conditions: hypertension, heart disease, diabetes, cancer, stroke, chronic bronchitis, emphysema, current asthma, and kidney disease) grew 22%. Clearly, multimorbidity will play a growing role in routine medical practice.
MULTIMORBIDITY AND HEALTH OUTCOMES
Multimorbidity is associated with a number of negative health outcomes, including accelerated declines in functional status, increased symptom burden, reduced quality of life, and mortality. Increasing numbers of chronic conditions place older adults at higher risk of hospitalization and nursing home placement. Accordingly, increased costs of care follow increased numbers of chronic conditions. In a study of more than one million Medicare beneficiaries, when seven conditions were considered, average per-person cost of care increased from $211 per year with no chronic conditions to $1870 with two or more conditions to $8159 for those with five conditions. Those with seven or more conditions averaged >$23,000 in costs per year. As health care systems become increasingly accountable for care across care settings, development of effective approaches to support older adults with multimorbidity will likely become a growing priority.
Clinicians caring for older adults with multimorbidity face a number of challenges in their management. This is true for both specialists and primary care clinicians. First, there is a disturbing lack of evidence for specific treatments among those with multiple chronic conditions as these individuals are commonly excluded from clinical trials. In a study examining a sample of randomized controlled trials (RCTs) published from 1995 to 2010 in the five highest-impact-factor general medical journals, individuals with multimorbidity were excluded in 63% of the 284 RCTs identified. In a separate examination of 11 Cochrane reviews evaluating clinical trials of treatments for four chronic diseases (diabetes mellitus [DM], heart failure, chronic obstructive pulmonary disease [COPD], and stroke), less than half described the prevalence among trial participants of any comorbidity co-occurring with the index condition. In addition to being excluded from many RCTs, multimorbidity is often not accounted for in clinical guidelines. If clinical practice guidelines for a particular condition acknowledge ...