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Understanding Mortality (Death) Rates

The term “mortality rate” in health care refers to the number of people that died from their illness or injury at the hospital. This is calculated by taking the number of people that died and dividing it by the total number of patients that were seen. For example, if a hospital sees 1,000 patients and 10 of those patients die, the mortality rate would be:

10 patients that died / 1,000 patients seen = 1% mortality rate

The mortality rate does not compare “apples to apples” because it assumes all patients are the same—however, we know that the types of patients and the severity of their illnesses are different. For example, a 70-year-old patient who comes to the hospital for a heart attack and a history of diabetes and high blood pressure is more likely to die than a 40-year-old patient who comes into the hospital for a heart attack with no previous medical problems.

Academic medical centers (AMCs), like UTMB Health, provide higher levels of specialized patient care and provide advanced treatments and surgeries. The patients that go to AMCs are typically sicker than those at community hospitals; thus, AMCs tend to have a higher rate of mortality.

At UTMB Health, we use the mortality index to compare ourselves to other hospitals as well as our mortality rates for patients with different types of illnesses.


How is Mortality Index Calculated?

Actual Mortality Rate

The actual mortality is the percentage of patients that died during a given time period. It is calculated by dividing the number of actual deaths in the group of patients by the total number of patients.

Expected Mortality Rate

The expected mortality represents the percentage of patients that were expected to die during a given time period. UTMB Health’s expected mortality is calculated by a company called Vizient. Vizient reviews patient data from hundreds of hospitals from across the nation. ┬áThe expected mortality is risk-adjusted, meaning that other factors (such as age, race, other illnesses, and the severity of their illnesses) are considered.

Mortality Index

The mortality index compares the actual mortality rates to the expected mortality rates. The mortality rate is calculate by dividing the actual mortality rate by the expected mortality rate.

A score of 1 means that the number of patients that died were predicted to pass away. A score of less than 1 means that more patients survived than were predicted to. A score of more than 1 means that more patients passed away than were predicted to. So, a lower the score is better.

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