Ask an Epi: Morbidity vs. Mortality Rate

Question: What's the difference between morbidity and mortality rate?

I've been asked more than a few times about the difference between morbidity and mortality. While they are often mentioned in the same breath, they refer to very different things. Here’s why:

Morbidity is the condition of being ill, diseased, or unhealthy. This can include acute illnesses (which have a sudden onset and improve or worsen in a short period of time), as well as chronic illnesses (which can present and progress slowly over a long period of time). An example of an acute illness can be the flu, a broken arm, or a heart attack. Chronic illnesses are more like diabetes, chronic obstructive pulmonary disorder (COPD), or cancer. A person can live for several years with one or more morbidities. One morbidity may lead to another morbidity.

Mortality, on the other hand, is the condition of being dead. You usually hear of mortality in terms of the number of deaths in a population over time, either in general or due to a specific cause. It’s important to recognize that morbidities may or may not lead to mortality. As an example, one could have terminal lung cancer, but die of injuries after a road accident.

On a national level, you can obtain morbidity and mortality data from the Centers for Disease Control and Prevention’s (CDC’s) Morbidity and Mortality Weekly Report (MMWR). The CDC WONDER (Wide-ranging Online Data from Epidemiological Research) database also collects these data which can be found in the LiveStories data library.

Here are examples of U.S. morbidity and mortality diabetes data from our library: 

Morbidity: Percent with Diabetes

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Source: CDC's Behavioral Risk Factor Surveillance System (BRFSS)

Mortality: Diabetes Deaths per 100,000

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Source: CDC WONDER, diabetes among multiple causes of death (MCD)

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Sofia Husain is a Customer Success Manager and Epidemiologist at LiveStories. She is an advocate for customers, helping them use LiveStories most effectively by understanding their data analysis and communication needs.