Comorbidity refers to the coexistence of two or more medical conditions in a single patient. A person with diabetes who also has hypertension has two comorbidities. The conditions may be related (obesity and type 2 diabetes often occur together) or independent.
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Comorbidity shows up in clinical decision-making, health insurance, and epidemiology. When a provider says a patient has “multiple comorbidities,” they’re flagging that treatment decisions are more complex — each condition affects the others, and medications can interact.
In population health and public health reporting, comorbidity data helps identify at-risk groups. During the COVID-19 pandemic, “patients with comorbidities” became a frequently cited risk category.
In health insurance and billing, comorbidities influence reimbursement rates. More comorbidities generally mean higher-acuity care, which affects how claims are coded and paid.
Comorbidity vs. complication
A comorbidity is a pre-existing or co-occurring condition. A complication is a new problem that arises because of a treatment or procedure. A patient who has asthma (comorbidity) and develops pneumonia after surgery (complication) illustrates the difference.
Source: World Health Organization (WHO) disease classification framework