I am doing a search on how the number of conditions can cause disease burden. I came across the terms comorbidity and multimorbidty in my search and I wanted to know the difference between the two.

Here are some definitions I found, and I was hoping someone might clear them up for me?

comorbidity – describes medical conditions that exist at the time of diagnosis of the index disease or later, but that are not a consequence of the index disease

multimorbidity – coexistence of several chronic diseases; can be described as existence of two or more chronic diseases.

2 Answers 2


Comorbidity describes the presence of one or more conditions beside another condition of interest. It can also refer to each of these accompanying conditions. For example:

  • Comorbidity (or comorbidities) of x usually include(s) y and z.

  • In a study of patients with type 2 diabetes (the main in the study), common comorbidities may include obesity, hypertension, coronary artery disease, among others.

Multimorbidity, refers merely to coexistence of multiple (>=2) conditions, without specifying a main condition of interest. For example:

  • A patient with multi-morbidity has the conditions x, y, and z at the same time.

  • A patient with coronary artery disease, obesity and hypertension is a patient with multimorbidity. S/he is likely to be on polypharmacy (taking multiple medications for those coexisting conditions).


Comorbidity and multimorbidity are both terms that we use when someone is diagnosed with two or more conditions.

Multimorbidity: Mrs Jones lives with dementia, osteoporosis, hypertension and diabetes. We are putting equal emphasis on all three conditions.

Comorbidity: Mrs Jones is living with dementia. She is also diagnosed with osteoporosis, hypertension and diabetes. The focus is on her dementia. The osteoporosis, hypertension and diabetes are referred to here as comorbidities.


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