Hospital Mortality Rates: What the Numbers Really Mean
Hospital mortality rates measure how often patients die during or shortly after a hospital stay. These statistics are among the most important quality indicators, but understanding what they truly represent requires looking beyond the raw numbers.
What Are Hospital Mortality Rates?
Hospital mortality rates typically measure the percentage of patients who die within 30 days of being admitted for specific conditions. CMS tracks mortality rates for several conditions:
- Heart attack (AMI): 30-day mortality after admission for acute myocardial infarction
- Heart failure: 30-day mortality after admission for heart failure
- Pneumonia: 30-day mortality after admission for pneumonia
- Stroke: 30-day mortality after admission for stroke
- COPD: 30-day mortality after admission for chronic obstructive pulmonary disease
- CABG surgery: 30-day mortality after coronary artery bypass graft surgery
How CMS Reports Mortality Data
Rather than reporting raw percentages, CMS compares each hospital's mortality rate to the national average using three categories:
- "Better than the national average": The hospital has statistically significantly lower mortality for this condition
- "No different than the national average": The hospital's mortality rate is within the expected range
- "Worse than the national average": The hospital has statistically significantly higher mortality
Risk Adjustment: Why Raw Numbers Can Be Misleading
CMS applies risk adjustment to account for differences in patient populations. This means the rates are adjusted for factors like:
- Patient age
- Severity of illness at admission
- Pre-existing conditions (comorbidities)
- Other clinical risk factors
Without risk adjustment, hospitals that treat sicker, older, or more complex patients would appear to have worse outcomes even if they provide excellent care.
What Mortality Rates Tell You
- How a hospital performs relative to peers for specific conditions
- Whether there are statistical concerns about outcomes at a particular hospital
- Trends over time (improving, stable, or declining performance)
What They Don't Tell You
- Mortality rates don't capture quality of life after treatment
- They may not reflect a hospital's performance for conditions not measured
- Small hospitals may not have enough cases for statistically meaningful comparisons
- Some hospitals may have higher mortality because they accept more transfer patients in critical condition
How to Use Mortality Data
- Check the mortality comparison for the specific condition relevant to your care
- Look for hospitals rated "Better than" or "No different than" the national average
- If a hospital is rated "Worse than" the national average, discuss this with your physician
- Compare multiple hospitals at Medicare Care Compare
Data sourced from CMS. Visit Medicare Care Compare or call 1-800-MEDICARE for hospital quality information.
Disclaimer: This article is for informational purposes only and does not constitute medical advice.
Important
This article explains how hospital quality data works and is for general information only. It is not medical advice and must not be used to decide whether to seek, delay or refuse care — that is a decision for you and a clinician who knows your situation.
CMS quality measures describe care delivered during earlier reporting periods and are refreshed roughly quarterly. A hospital's staffing, services and performance can change well before the published numbers do.
hospiguide.org is not affiliated with, endorsed by, or connected to CMS, Medicare, or any U.S. government agency, and publishes no ratings of its own.
Before acting on anything here, verify current details at Medicare.gov Care Compare or call 1-800-MEDICARE (1-800-633-4227), TTY 1-877-486-2048.
HospiGuide.org Editorial Team
Our editorial team explains U.S. hospital quality data using official CMS datasets and government publications. We are not medical professionals, we do not recommend hospitals, and we accept no payment for coverage. Every factual claim is checked against a CMS or federal source. Read our editorial policy.
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