U.S. Department of Health and Human Services 
 Office of Inspector General 
 
Data Brief 
 
 September 2021, OEI-02-20-00410 
 
 
Medicare Beneficiaries Hospitalized With COVID-19 Experienced a 
Wide Range of Serious, Complex Conditions 
Coronavirus disease 2019 (COVID-19) has affected millions of 
Key Takeaways  Americans, resulting in more than 600,000 deaths.1  Medicare 
beneficiaries have been particularly affected and remain 
o  Medicare beneficiaries 
vulnerable to new variants and additional surges of the virus.  
hospitalized with COVID-19 were 
treated for a wide range of  Clinicians and researchers are still working to fully understand the 
complex conditions such as  damage to the body from the disease and what underlying 
acute respiratory failure, kidney  chronic conditions potentially lead to more severe complications 
failure, and sepsis.  or hospitalization. 
 
o  More than half of hospitalized  Understanding the types of conditions for which Medicare 
Medicare beneficiaries with  beneficiaries with COVID-19 are being treated and who was more 
COVID-19 received intensive  likely to be hospitalized with COVID-19 can help hospitals and 
care or mechanical ventilation.   
health officials better prepare for and address the wide-ranging 
 
and extensive needs of COVID-19 patients, particularly in the 
o  Dually eligible, Black, Hispanic,  event of localized surges of cases.  Such knowledge will also assist 
or older beneficiaries were 
in the Federal, State, and local response to the pandemic by 
disproportionately hospitalized 
providing a better picture of the needs of these hospitalized 
with COVID-19. 
beneficiaries.   
This report describes the complex care needs of beneficiaries hospitalized with COVID-19.  It focuses on 
surges in COVID-19 hospitalizations in six localities and builds upon prior OIG work that describes the 
extent to which hospitals have been strained by COVID-19.2  As we noted in the 2021 report about 
hospital experiences during the pandemic, hospitals have been operating in "survival mode" for an 
extended period of time.  They have also experienced difficulty balancing the complex and resource-
intensive care needed for COVID-19 patients with efforts to resume routine hospital care. 
How OIG Did This Review 
We reviewed hospital inpatient claims and enrollment data to identify all Medicare beneficiaries who 
were hospitalized in a short-term acute-care hospital at any point from April 1 through July 31, 2020.  
We then identified six localities that experienced a surge in hospitalizations of Medicare beneficiaries 
with COVID-19 over a 3-week period.3  We analyzed the diagnoses on the claims of beneficiaries 
hospitalized with COVID-19 in those six selected localities to identify the conditions for which they were 
treated during their hospital stays.  The percentages presented in this report represent averages among 
the six localities. 
 
 
 
  What OIG Found  
During surges in hospitalizations, hospitals in the six localities treated Medicare beneficiaries with 
COVID-19 for a wide range of serious, complex conditions.  Almost all of these beneficiaries were 
treated for acute respiratory issues, such as viral pneumonia.  Many of these beneficiaries were also 
treated for other types of serious conditions including: 
  almost half were treated for acute kidney failure,  
  almost half had acute circulatory issues, 
  almost two-thirds were treated for significant endocrine, nutritional, or metabolic issues, and 
  more than one-third had sepsis. 
More than 50 percent of Medicare beneficiaries hospitalized with COVID-19 received intensive care or 
mechanical ventilation.  Additionally, dually eligible, Black, Hispanic, or older beneficiaries were 
disproportionately hospitalized with COVID-19 relative to the Medicare population in these localities.   
What OIG Concludes  
The complex needs of hospitalized Medicare beneficiariescombined with surges in hospitalizations
may create substantial challenges in meeting the needs of these patients, particularly in light of the 
staffing and other problems that hospitals have reported.  Gaining a better understanding of Medicare 
beneficiaries hospitalized with COVID-19including the conditions for which they were being treated 
and demographic characteristicscan assist Federal, State, and local efforts during the COVID-19 
pandemic and may be used to provide additional guidance to hospitals.  This information can also help 
hospitals, physicians, and other practicioners better prepare for the complex and resource-intensive 
care needs of Medicare beneficiaries with COVID-19, which may be particularly important during 
continued surges of the virus.  CMS can also use this information to identify beneficiaries who are 
particularly vulnerable to hospitalization as well as to understand the needs of these beneficiaries 
during their hospitalizations.  In addition, this analysis shows that Medicare claims data can be used to 
enhance knowledge of the treatment of COVID-19 and help inform additional research efforts. 
 
 
 
  Primer on hospitalizations of Medicare beneficiaries with COVID-19 
 
Many localities experienced extremely high rates of hospitalizations of Medicare beneficiaries with 
COVID-19.4  From April through July 2020, more than 274,000 Medicare beneficiaries were hospitalized 
with COVID-19; however, these hospitalizations were not evenly distributed across the Nation.  For 
additional information about how localities across the Nation were affected over time, see the 
interactive map at the HHS-OIG Geo Hub.5 
This report focuses on 55,000 beneficiaries hospitalized with COVID-19 in six localities.  These localities 
stood out as each having a high rate of COVID-19 hospitalizations that was concentrated within a 
relatively short period of time.  (See Exhibit 1 below.)  These six selected localitiesDetroit, Houston, 
Miami, New Orleans, New York City, and Phoenixeach experienced a surge of COVID-19 
hospitalizations over a 3-week period.6  Notably, during the surge in New York City, more than 1 out of 
every 100 Medicare beneficiaries were hospitalized with COVID-19with almost 35,000 such 
hospitalizations within just 3 weeks.  When there are marked surges in hospitalizations, hospitals may 
be challenged in meeting the resource-intensive needs of Medicare beneficiaries.  This report describes 
the complex care needs of beneficiaries hospitalized with COVID-19 during these surges in 
hospitalizations.  Note that unless otherwise specified, the figures and percentages presented in this 
report represent the average across the six localities.  See Appendix A for more information on COVID-
19 hospitalizations by locality. 
Exhibit 1: Six localities experienced a surge of Medicare COVID-19 hospitalizations over a 3-
week period. 
 
Source: OIG analysis of Medicare data, 2021.   
RESULTS 
 
Hospitals needed to treat Medicare beneficiaries with COVID-19 
for a wide range of serious, complex conditions  
Medicare beneficiaries who were hospitalized with COVID-19 suffered from a 
multitude of acute conditions that require significant medical attention.  They also 
had a number of chronic conditions that may have put beneficiaries at risk for severe 
outcomes of COVID-19 or may have been exacerbated by the virus.7     
Although it is well understood that 
COVID-19 commonly results in 
significant respiratory conditions for 
hospitalized patients, COVID-19 can 
extend to many other organ systems 
including the heart, kidneys, and 
endocrine system.  In some cases, it 
may also lead to sepsis.8  Hospitals treated beneficiaries with COVID-19 for these 
serious, complex conditions during surges in hospitalizations in the six localities.9 
Often these serious and complex conditions resulted in longer lengths of stay in the 
hospital.  The average length of stay for Medicare beneficiaries diagnosed with 
COVID-19 was 12 days, with 13 percent of stays lasting longer than 3 weeks.  This 
compares to an average length of stay of 8 days for beneficiaries without COVID-19.  
Additionally, 90 percent of these hospitalizations were emergency admissions, which 
involve immediate medical intervention as a result of severe, life-threatening, or 
potentially disabling conditions.  See Appendix B for more information on lengths of 
stay and hospital admissions by locality. 
Almost all Medicare beneficiaries hospitalized with COVID-19 
were treated for acute respiratory issues, such as viral pneumonia 
On average, 91 percent of beneficiaries hospitalized with COVID-19 during a surge 
were treated for common acute respiratory conditions.  Specifically, 86 percent were 
treated for viral pneumonia.  A smaller proportion of beneficiaries were treated for 
pneumonia due to a secondary infection, such as bacterial pneumonia.  According to 
one expert, this is likely due to a complication of the inflammatory response or 
damage to lung tissue. 
Data Brief: Medicare Beneficiaries Hospitalized With COVID-19 Experienced a Wide Range of Serious, Complex Conditions 
OEI-02-20-00410  Results | 4  Almost two-thirds of beneficiaries were 
treated for acute respiratory failure  Common Acute Respiratory 
while an additional 11 percent were  Ailments for Beneficiaries 
treated for a more severe type of  Hospitalized With COVID-19 
respiratory failureacute respiratory   
distress syndrome (ARDS).  ARDS  86% were treated for viral 
occurs when fluid builds up in the  pneumonia 
lungs, often depriving other organs of  60% were treated for acute 
the oxygen they need to function; it  respiratory failure 
typically occurs in people who are  11% were treated for ARDS 
already critically ill or who have  8% were treated for pneumonia due 
significant injuries.  to secondary infection 
Twenty-five percent of Medicare 
beneficiaries hospitalized with COVID-19 also had chronic respiratory issues.  An 
average of 18 percent of beneficiaries 
had a diagnosis of chronic obstructive  1 in 4 
had chronic lower 
pulmonary disease (COPD) and 6 
respiratory conditions or chronic 
percent had asthma.  Five percent of 
 
respiratory failure.
Medicare beneficiaries had a diagnosis 
of chronic respiratory failure.   
Almost half of Medicare beneficiaries hospitalized with COVID-19 
were treated for acute kidney failure 
Medicare beneficiaries who were 
hospitalized with COVID-19 during a  Common Acute Kidney Ailments for 
surge were frequently treated for acute  Beneficiaries Hospitalized With 
diseases of the renal system.  On  COVID-19 
average, 47 percent of beneficiaries   
were treated for acute kidney failure.   47% were treated for acute kidney 
Early research suggests that COVID-19  failure 
can cause severe damage to many  15% were treated for urinary tract 
organs and that kidney damage from  infections 
COVID-19 can be severe enough to 
require dialysis.10  Kidney or other 
organ failure may also be a warning sign of severe sepsis.  
Beneficiaries hospitalized with COVID-19 were also often treated for urinary tract 
infections (UTIs).  UTIs are one of the most common infectious diseases in adults age 
65 and older and can have serious complications including fever and diminished 
cognitive function. 
Data Brief: Medicare Beneficiaries Hospitalized With COVID-19 Experienced a Wide Range of Serious, Complex Conditions 
OEI-02-20-00410  Results | 5  While some beneficiaries with 
COVID-19 were treated for acute  1 in 5 
were treated for chronic 
kidney injury, a large number were 
kidney failure or end-stage renal 
treated for chronic kidney conditions.  
disease.   
An average of 12 percent of 
beneficiaries with COVID-19 had a 
diagnosis of chronic kidney disease and an additional 8 percent had a diagnosis of 
end-stage renal disease.  End-stage renal disease is the final stage of chronic kidney 
disease in which permanent damage to the kidneys causes a complete loss of 
function and a dependence on dialysis or transplant.   
Almost half of Medicare beneficiaries hospitalized with COVID-19 
were treated for acute circulatory issues, such as heart attack or 
stroke 
On average, 44 percent of beneficiaries 
hospitalized with COVID-19 during a  Common Acute Circulatory 
surge were treated for acute circulatory  Ailments for Beneficiaries 
conditions.  Specifically, an average of  Hospitalized With COVID-19 
24 percent of beneficiaries with   
COVID-19 were treated for irregular  24% were treated for irregular heart 
heart rates (known as atrial fibrillation  rates 
or cardiac arrhythmia), 14 percent were  14% were treated for acute heart 
treated for acute heart failure, 8  failure 
percent were treated for a heart attack  8% were treated for heart attacks 
(also known as an acute myocardial  7% were treated for blood clotting 
infarction), and 7 percent were treated  issues 
for blood clotting issues such as  3% were treated for stroke or TIAs 
coagulopathy, embolism, or 
thrombosis.  Additionally, 3 percent of beneficiaries on average were treated for 
stroke or transient ischemic attacks (TIAs).  
Almost all Medicare beneficiaries 
hospitalized with COVID-19 also had   4 in 5
More than  were treated for 
chronic circulatory issues.  On average, 
chronic circulatory issues.   
83 percent of beneficiaries were treated 
for chronic hypertensive diseases such 
as high-blood pressure and 25 percent were treated for chronic ischemic heart 
diseases.  Fifteen percent of beneficiaries were treated for chronic heart failure.  
Hypertension and chronic heart conditions can increase the risk of severe illness from 
COVID-19.11 
Data Brief: Medicare Beneficiaries Hospitalized With COVID-19 Experienced a Wide Range of Serious, Complex Conditions 
OEI-02-20-00410  Results | 6  Almost two-thirds of Medicare beneficiaries hospitalized with 
COVID-19 had significant endocrine, nutritional, or metabolic 
issues 
Medicare beneficiaries hospitalized 
with COVID-19 during a surge were  Common Acute Endocrine, 
commonly treated for significant acute  Nutritional, and Metabolic Ailments 
endocrine, nutritional, or metabolic  for Beneficiaries Hospitalized With 
issues such as dehydration.  On  COVID-19 
average, 65 percent of beneficiaries   
were treated for these  24% were treated for low sodium 
conditions.  Most commonly, this  21% were treated for excess acid 
included treatment for both low and  20% were treated for high sodium 
high sodium levels in the blood  19% were treated for low potassium 
(hyposmolality/hyponatremia and  17% were treated for dehydration 
hyperosmolality/hypernatremia,  15% were treated for high potassium 
respectively), excess acid in the blood 
(acidosis), and both low and high 
potassium in the blood (hypokalemia and hyperkalemia, respectively).  Hyposmolality 
and hyponatremia can be caused by systemic inflammation from an infection.  
Hyperosmolality and hypernatremia can be caused by several different factors, 
including dehydration and loss of water.  Acidosis is caused by an excess of carbon 
dioxide in the blood and can be due to poor lung function.  Similarly, excess 
potassium in the blood can be due to poor kidney function and kidney disease. 
Additionally, many Medicare 
beneficiaries hospitalized with  1 in 2
 were treated for diabetes.   
COVID-19 also had chronic endocrine, 
nutritional, and metabolic issues.  
Almost half of Medicare beneficiaries hospitalized with COVID-19 were treated for 
diabetes.12  On average, 48 percent of beneficiaries hospitalized with COVID-19 had 
type 2 diabetes.  This included 20 percent who had type 2 diabetes with chronic 
kidney disease, 17 percent who had type 2 diabetes with hyperglycemia, and 14 
percent of beneficiaries who had type 2 diabetes without complications.  Research 
suggests having type 2 diabetes increases the risk of severe illness from COVID-19.13  
See Appendix C for a list of conditions for which Medicare beneficiaries hospitalized 
with COVID-19 were commonly treated. 
More than one-third of Medicare beneficiaries hospitalized with 
COVID-19 were treated for sepsis 
Sepsis is an extreme, life-threatening reaction to an infection causing a systemic 
inflammatory response and organ dysfunction in severe cases.  On average, 36 
Data Brief: Medicare Beneficiaries Hospitalized With COVID-19 Experienced a Wide Range of Serious, Complex Conditions 
OEI-02-20-00410  Results | 7  percent of beneficiaries hospitalized with COVID-19 during a surge were diagnosed 
with sepsis. 
 
Severe sepsis is organ dysfunction caused 
 1 in 3
by the extreme host response to  More than  were treated 
infection.  Severe sepsis can occur with or  for sepsis.   
without septic shock.  On average, 53 
percent of the COVID-19 beneficiaries with sepsis had severe sepsis.  These 
beneficiaries require extra management and medical resources. 
The proportion of hospitalized beneficiaries with COVID-19 who were diagnosed with 
sepsis varied across the six localities, ranging from 28 percent in Miami to 41 percent 
in Detroit and Houston.  The proportion of beneficiaries with severe sepsis also varied 
across the six localities.  Notably, Miami and New Orleans had the highest proportions 
of severe sepsis among beneficiaries with sepsis (55 percent and 60 percent, 
respectively).   
See Appendix D for the proportion of beneficiaries with sepsis and severe sepsis by 
locality. 
Medicare beneficiaries hospitalized with COVID-19 often 
received intensive care or mechanical ventilation 
Because COVID-19 can cause severe damage to multiple organ systems, a significant 
proportion of beneficiaries may require care in an intensive care unit (ICU) or need 
mechanical ventilation.  On average, 51 percent of beneficiaries hospitalized with 
COVID-19 during a surge received either care in an ICU or mechanical ventilation.  
These beneficiaries use significant hospital resources and often have longer stays in 
the hospital. 
Almost half of beneficiaries hospitalized with COVID-19 received 
care in the ICU 
On average, 49 percent of beneficiaries hospitalized with COVID-19 during a surge 
received care in the ICU.  Hospitals with a high proportion of beneficiaries requiring 
care in the ICU may be particularly strained, as beneficiaries who receive care in the 
ICU typically require the highest levels of care available.  
Beneficiaries requiring care in ICUs often had longer stays in the hospital, staying an 
average of 7 days longer than beneficiaries not receiving care in the ICU.14  Certain 
conditions were more common among beneficiaries receiving care in the ICU, 
including sepsis and severe sepsis with septic shock, ARDS, and endocrine, nutritional, 
and metabolic issues such as hyperkalemia and acidosis.   
Interestingly, there was significant variation in the percentage of COVID-19 
beneficiaries receiving care in the ICU.  Localities ranged from 26 percent in New York 
Data Brief: Medicare Beneficiaries Hospitalized With COVID-19 Experienced a Wide Range of Serious, Complex Conditions 
OEI-02-20-00410  Results | 8  City to 71 percent in Phoenix.  This may be due to certain hospitals being able to 
expand capacity with new or temporary units.  One expert in quality and patient 
safety noted an example of a hospital that tripled its ICU capacity during a surge in 
hospitalizations.  However, as another expert noted, hospitals may experience 
difficulty staffing these units with trained critical care nurses and physicians.  Without 
enough appropriately trained doctors and nurses, hospitals cannot provide 
appropriate care to such a high number of critically ill patients.   
Conversely, some localities may not 
have been able to expand their ICU 
capacity during a surge in beneficiaries 
with COVID-19.  This may have resulted 
in the hospitals providing higher levels 
of care to patients in other areas of the 
hospital.  For example, mechanical 
ventilation is typically administered in 
the ICU, but capacity limitations may 
require a hospital to keep patients in 
other units.  This was the case for 
31 percent of beneficiaries in New York 
City compared to only 2 percent in Phoenix.  See Appendix E for more information on 
ICU utilization by locality. 
More than one-fifth of beneficiaries hospitalized with COVID-19 
required the assistance of a ventilator 
Because COVID-19 can damage the respiratory system and impair lung function, 
some patients may require use of a ventilator.15  On average, 22 percent of 
beneficiaries hospitalized with COVID-19 during a surge received mechanical 
ventilation.  There was little variation in use of mechanical ventilation in the localities 
that experienced a surge at different times despite discussion in the medical literature 
about changing practices regarding mechanical ventilation.16   
Beneficiaries who received mechanical ventilation often had longer stays in the 
hospital, staying an additional 10 days on average, compared to beneficiaries with 
COVID-19 who did not receive mechanical ventilation. 
Certain conditions were more common among beneficiaries with COVID-19 who 
received mechanical ventilation such as sepsis and severe sepsis with septic shock, 
ARDS, and acute kidney failure.  
 
Data Brief: Medicare Beneficiaries Hospitalized With COVID-19 Experienced a Wide Range of Serious, Complex Conditions 
OEI-02-20-00410  Results | 9  Dually eligible, Black, Hispanic, or older beneficiaries were 
disproportionately hospitalized with COVID-19  
Medicare beneficiaries in certain demographic groups were disproportionately 
hospitalized with COVID-19 during a surge relative to the total Medicare population 
in these six localities.  Longstanding health and social inequalities may have resulted 
in certain groups having an increased risk of illness and an increased risk of 
hospitalization with COVID-19.17  Differences in wealth, health care access, and race 
and ethnicity are interrelated and influence a wide range of health and quality-of-life 
outcomes and risks.18  See Exhibit 2 for additional information about beneficiary 
characteristics in the six localities and Appendix F for more information on beneficiary 
characteristics for each locality. 
Exhibit 2: Medicare beneficiaries in certain demographic groups were 
disproportionately hospitalized with COVID-19 compared to the Medicare 
population. 
 
Source: OIG analysis of Medicare data during a surge in six selected localities, 2021. 
Dually eligible beneficiariesthose enrolled in both Medicare and Medicaidwere 
disproportionately hospitalized with COVID-19 during a surge.  Dually eligible 
beneficiaries include beneficiaries who are eligible due to age or disability and low 
income.  These beneficiaries are typically poorer and sicker than other Medicare 
beneficiaries.19  On average, 47 percent of beneficiaries who were hospitalized with 
COVID-19 were dually eligible.  In comparison, dually eligible beneficiaries represent, 
on average, only 20 percent of Medicare beneficiaries in the six localities. 
Beneficiaries from certain racial and ethnic groups were also disproportionately 
hospitalized with COVID-19 during a surge.  On average, 33 percent of beneficiaries 
hospitalized with COVID-19 were Black and 23 percent were Hispanic.  This is much 
Data Brief: Medicare Beneficiaries Hospitalized With COVID-19 Experienced a Wide Range of Serious, Complex Conditions 
OEI-02-20-00410  Results | 10  higher than the Medicare population in the 6 localities, where on average 18 percent 
of beneficiaries are Black and 6 percent are Hispanic.  
In addition, older beneficiaries were disproportionately hospitalized with COVID-19 
during a surge.  On average, 31 percent of beneficiaries who were hospitalized with 
COVID-19 were between 75 and 84 years of age.  In comparison, beneficiaries in this 
age group represented an average of 25 percent of the Medicare population in the six 
localities.  Similarly, beneficiaries who were 85 years and older were also 
disproportionately hospitalized with COVID-19.  On average, 20 percent of 
beneficiaries who were hospitalized with COVID-19 were 85 and older, while they 
represent only 11 percent of the population. 
Men were also disproportionately hospitalized with COVID-19 during a surge.  On 
average, 51 percent of beneficiaries who were hospitalized with COVID-19 were men; 
however, men represented 45 percent of Medicare beneficiaries in the six localities. 
Data Brief: Medicare Beneficiaries Hospitalized With COVID-19 Experienced a Wide Range of Serious, Complex Conditions 
OEI-02-20-00410  Results | 11   
CONCLUSION  
 
 
This report provides insights into the care needs of beneficiaries with COVID-19 and 
the disproportionate hospitalization rates for beneficiaries in certain demographic 
groups.  Beneficiaries hospitalized with COVID-19 were treated for a wide range of 
serious and complex conditions.  Although it is well understood that COVID-19 
commonly results in significant respiratory conditions for hospitalized patients 
(affecting an average of 91 percent of hospitalized beneficiaries), COVID-19 can also 
extend to many other organ systems including the heart, kidneys, and endocrine 
system.  Medicare beneficiaries experienced a number of potentially life-threating 
acute conditions in addition to a number of chronic conditions that were potentially 
exacerbated by the virus.  For example, almost half of beneficiaries with COVID-19 
were treated for acute circulatory issues such as acute heart failure, heart attack, or 
stroke.  Perhaps even more concerning, more than one-third of hospitalized 
beneficiaries developed sepsis, which is a serious reaction to an infection causing a 
systemic inflammatory response, resulting in organ failure in severe cases.  
Additionally, on average 51 percent of Medicare beneficiaries received intensive care 
or mechanical ventilation.  We also found that dually eligible, Black, Hispanic, or older 
beneficiaries were disproportionately hospitalized with COVID-19 during these surges. 
Gaining a better understanding of Medicare beneficiaries hospitalized with 
COVID-19including the conditions for which they were being treated and 
demographic characteristicscan assist Federal, State, and local efforts in the COVID-
19 pandemic and may be used to provide additional guidance to hospitals.   This 
information can also help hospitals, physicians, and other practicioners better prepare 
for the complex and resource-intensive care needs of Medicare beneficiaries with 
COVID-19, which may be particularly important during continued surges of the virus.  
Furthermore, this report expands on CMSs analysis of Medicare beneficiaries with 
COVID-19.20  CMS can use this information to identify beneficiaries who are 
particularly vulnerable to hospitalization as well as understand the needs of these 
beneficiaries during their hospitalizations.  In addition, this analysis shows that 
Medicare claims data can be used to enhance knowledge of the treatment of COVID-
19 and help inform additional research efforts. 
Data Brief: Medicare Beneficiaries Hospitalized With COVID-19 Experienced a Wide Range of Serious, Complex Conditions 
OEI-02-20-00410  Conclusion | 12   
METHODOLOGY 
 
 
We reviewed hospital inpatient claims and enrollment data for all beneficiaries who 
were hospitalized in a short-term acute-care hospital at any point from April 1, 2020, 
through July 31, 2020.  We included Medicare fee-for-service claims data and 
Medicare Advantage encounter data from CMSs National Claims History file and 
Medicare enrollment information.  We conducted our analysis in mid-2021 to allow 
time for claims to be finalized.21 
Analysis of Hospitalized Medicare Beneficiaries With COVID-19 by 
Locality 
We first determined the extent to which Medicare beneficiaries were hospitalized with 
COVID-19 in each locality across the country.  For the purposes of our analysis, we 
considered a locality to be a Core-Based Statistical Area (CBSA).22  We focused our 
analysis on the 831 of 939 CBSAs that each had a short-term acute-care hospital.  
We analyzed all Medicare inpatient hospital claims to identify the number of 
beneficiaries who were hospitalized with COVID-19 in each locality from April 1, 2020, 
through July 31, 2020.  We excluded claims from hospitals that were not paid under 
the Inpatient Prospective Payment System (IPPS), such as long-term care hospitals 
and critical-access hospitals.23  We considered beneficiaries with a diagnosis code of 
U07.1 to be diagnosed with COVID-19.24 
Selection of Six Localities With Surges in COVID-19 
Hospitalizations 
We determined the extent to which hospitalization rates changed over time.  To do 
this, we used the number of Medicare COVID-19 hospitalizations for each day from 
April 1, 2020, through July 31, 2020, for each locality and the total number of 
Medicare beneficiaries who were enrolled in Medicare in that locality.25  Using the 
data from all localities, we selected a purposive sample of six localities that each had a 
high rate of Medicare COVID-19 hospitalizations concentrated within a short period 
of time.  For each of the 6 localities, we identified a surge that represented the 21 
consecutive days with the highest rate of Medicare COVID-19 hospitalizations.  We 
included three localities that experienced a surge in hospitalizations in April and three 
localities that experienced a surge in hospitalizations in July.26 
Analysis of Hospitalizations in Six Localities 
For each of the six localities, we analyzed the Medicare inpatient claims for all 
Medicare beneficiaries hospitalized during the 3-week surge.  Using these claims, we 
Data Brief: Medicare Beneficiaries Hospitalized With COVID-19 Experienced a Wide Range of Serious, Complex Conditions 
OEI-02-20-00410  Methodology | 13  determined the proportion of all hospitalized Medicare beneficiaries who had a 
diagnosis of COVID-19 in each of the six localities.  We analyzed the claims data to 
determine the average lengths of stay among beneficiaries hospitalized with COVID-
19.27  We also determined the proportion of beneficiaries with COVID-19 who had an 
emergency admission to the hospital.   
We determined the average proportion across the six localities by summing the 
proportion for each locality and dividing by six.  Each locality was given equal weight 
in determining the average.  Unless otherwise indicated, the percentages presented in 
this report represent the average among the six localities.  We highlighted the specific 
numbers in the individual localities when there were notable differences. 
Beneficiary Conditions  
We determined the extent to which Medicare beneficiaries hospitalized with 
COVID-19 during a surge in these in six localities were treated for key conditions.  To 
identify these conditions, we analyzed the ICD-10-CM diagnosis codes on the claims.  
ICD-10-CM codes are broadly grouped according to the organ system that the 
disease or condition affects.  We relied on these groupings to identify beneficiaries 
with conditions related to the circulatory system, the respiratory system, the 
genitourinary system (which includes conditions such as kidney ailments and UTIs), 
and the endocrine system.  
Within each of these organ systems, we identified the most common diagnoses and 
conditions for which beneficiaries were being treated.  We also used ICD-10-CM 
diagnosis codes to identify beneficiaries with certain chronic conditions, such as 
beneficiaries with a diagnosis of chronic obstructive pulmonary disease, or other 
notable conditions, such as beneficiaries treated for sepsis. 
In addition to identifying the most frequent conditions, we also consulted with 
medical experts and coding professionals to review the codes and help group them 
into relevant categories.  We also asked them to identify diagnoses that were likely 
linked to COVID-19 or were common chronic diagnoses that increased the risk of 
severe outcomes for COVID-19. 
Types of Care 
Next, we determined the types of care received by hospitalized Medicare beneficiaries 
with COVID-19, such as whether the beneficiaries received intensive care or 
mechanical ventilation.  To determine whether Medicare beneficiaries received 
intensive care, we relied on the revenue center codes listed on the hospital claims.  
These codes correspond to various hospital departments that furnished services to 
the beneficiary.  We reviewed the ICD-10-PCS procedure codes on the claims to 
determine the extent to which beneficiaries received mechanical ventilation.28   
 
Data Brief: Medicare Beneficiaries Hospitalized With COVID-19 Experienced a Wide Range of Serious, Complex Conditions 
OEI-02-20-00410  Methodology | 14  Analysis of Beneficiary Characteristics 
We analyzed data from the Medicare Enrollment Database for all beneficiaries who 
were hospitalized with COVID-19 in the six localities during the 3-week surge period.  
We used this information to describe key characteristics including age, sex, race and 
ethnicity, and eligibility status (e.g., whether a beneficiary was dually eligible for 
Medicare and Medicaid).  To serve as a comparison and to determine the extent to 
which beneficiaries with certain characteristics were disproportionately hospitalized 
with COVID-19, we analyzed enrollment data for all Medicare beneficiaries within 
each locality.  We analyzed the data across each locality to note the extent to which 
the beneficiary characteristics vary by locality. 
The race and ethnicity information is based on data collected from the Social Security 
Administration and an algorithm developed by the Research Triangle Institute.29  This 
algorithm attempts to improve the quality of the Social Security Administrations data 
by amending the race data for certain groups based on name and geography, as well 
as requests made by individuals for certain government materials to be provided in 
Spanish.  
Limitations 
This study is based on the diagnosis and other information on the Medicare claims; it 
is not based on a review of the medical records.  The diagnosis information on the 
claims should reflect the beneficiarys conditions.  However, the accuracy of diagnoses 
on the claims may be influenced by the information recorded by the clinician (e.g., an 
information omission) as well as the medical coder (because experience and training 
can influence precision in coding). 
The Social Security Administrations data on race and ethnicity upon which Medicare 
enrollment data are based have known limitations.  Although this information is 
currently the best available for the entire Medicare beneficiary population, 
comparisons to self-reported data (available in certain, limited circumstances) show 
that race and ethnicity is still misclassified for some beneficiaries.  In particular, 
Medicare beneficiaries with a race and ethnicity of American Indian/Alaska Native, 
Asian/Pacific Islander, or Hispanic are more likely to be misclassified.30 
Standards 
We conducted this study in accordance with the Quality Standards for Inspection and 
Evaluation issued by the Council of the Inspectors General on Integrity and Efficiency. 
Data Brief: Medicare Beneficiaries Hospitalized With COVID-19 Experienced a Wide Range of Serious, Complex Conditions 
OEI-02-20-00410  Methodology | 15   
APPENDIX A 
 
Hospitalizations of Medicare Beneficiaries With COVID-19 in Six 
Selected Localities During a Surge 
 
Total number of  Number of  Percentage of all 
beneficiaries  beneficiaries  hospitalized 
hospitalized with  hospitalized with  beneficiaries who had 
COVID-19  COVID-19 per 100K  COVID-19  
beneficiaries 
Detroit  5,889  696  46% 
Houston             3,687  416  26% 
Miami  5,794  512  32% 
New Orleans  1,668  701  44% 
New York City  34,690  1,047  67% 
Phoenix  2,929  368  25% 
 
Average  623  40% 
Source: OIG analysis of Medicare data, 2021. 
Data Brief: Medicare Beneficiaries Hospitalized With COVID-19 Experienced a Wide Range of Serious, Complex Conditions 
OEI-02-20-00410  Appendix A | 16   
APPENDIX B 
 
Lengths of Stay and Emergency Admissions Among Medicare 
Beneficiaries Hospitalized With COVID-19 in Six Selected 
Localities During a Surge 
Exhibit B-1: Average length of stay in the hospital for Medicare beneficiaries 
by locality, in days 
 
Average length of stay for  Average length of stay for 
beneficiaries with COVID-19  beneficiaries without COVID-19  
Detroit  10  7 
Houston  11  7 
Miami  13  8 
New Orleans  13  7 
New York City  11  9 
Phoenix  12  7 
Average  12  8 
Source: OIG analysis of Medicare data, 2021. 
Exhibit B-2: Emergency admissions among Medicare beneficiaries 
hospitalized with COVID-19 
 
Percentage of hospitalizations among Medicare 
beneficiaries with COVID-19 that were 
emergency admissions   
Detroit  90% 
Houston  92% 
Miami  88% 
New Orleans  93% 
New York City  96% 
Phoenix  79% 
Average  90% 
Source: OIG analysis of Medicare data, 2021. 
 
Data Brief: Medicare Beneficiaries Hospitalized With COVID-19 Experienced a Wide Range of Serious, Complex Conditions 
OEI-02-20-00410  Appendix B | 17   
APPENDIX C 
 
Common Conditions Among Medicare Beneficiaries 
Hospitalized With COVID-19 in Six Selected Localities During a 
Surge 
Exhibit C-1: Average percentage of beneficiaries hospitalized with COVID-19 
who were treated for common conditions 
Respiratory Conditions 
Acute respiratory failure  60% 
ARDS  11% 
Asthma  6% 
Chronic respiratory failure  5% 
COPD  18% 
Pneumonia due to secondary infection   8% 
Viral pneumonia  86% 
Kidney and Urinary Conditions 
Acute kidney failure  47% 
Chronic kidney disease  12% 
End-stage renal disease  8% 
UTI  15% 
Circulatory Conditions 
Acute heart failure  14% 
Acute myocardial infarction  8% 
Atrial fibrillation and cardiac arrhythmia  24% 
Chronic hypertensive diseases  83% 
Chronic ischemic heart diseases  25% 
Coagulation/embolism/thrombosis  7% 
Stroke or TIA  3% 
Endocrine, Nutritional, and Metabolic Conditions 
Dehydration  17% 
High acid (acidosis)  21% 
High potassium (hyperkalemia)  15% 
High sodium (hyperosmolality and hypernatremia)  20% 
Low potassium (hypokalemia)  19% 
Data Brief: Medicare Beneficiaries Hospitalized With COVID-19 Experienced a Wide Range of Serious, Complex Conditions 
OEI-02-20-00410  Appendix C | 18  Low sodium (hyposmolality and hyponatremia)  24% 
Type 2 diabetes with chronic kidney disease  20% 
Type 2 diabetes with hyperglycemia  17% 
Type 2 diabetes without complications  14% 
Note: Across the six localities, the percentages of beneficiaries with COVID-19 treated for these conditions were 
relatively similar for most conditions.  There were large differences in the percentages of beneficiaries hospitalized 
with COVID-19 treated for ARDS.  The respective percentage of beneficiaries hospitalized with COVID-19 who were 
treated for ARDS was 4 percent in Miami and 18 percent in New York City. 
Source: OIG analysis of Medicare data, 2021. 
Data Brief: Medicare Beneficiaries Hospitalized With COVID-19 Experienced a Wide Range of Serious, Complex Conditions 
OEI-02-20-00410  Appendix C | 19   
APPENDIX D 
 
Sepsis and Severe Sepsis Among Medicare Beneficiaries 
Hospitalized With COVID-19 in Six Selected Localities During a 
Surge 
 
Percentage of beneficiaries  Percentage of beneficiaries with 
hospitalized with COVID-19 treated  sepsis treated for severe sepsis 
for sepsis  
Detroit  41%  48% 
Houston  41%  55% 
Miami  28%  55% 
New Orleans  34%  60% 
New York City  36%  53% 
Phoenix  37%  44% 
Average  36%  53% 
Source: OIG analysis of Medicare data, 2021. 
 
 
 
 
 
Data Brief: Medicare Beneficiaries Hospitalized With COVID-19 Experienced a Wide Range of Serious, Complex Conditions 
OEI-02-20-00410  Appendix D | 20   
APPENDIX E 
 
Medicare Beneficiaries Hospitalized With COVID-19 Who 
Received Intensive Care and Mechanical Ventilation in Six 
Selected Localities During a Surge 
 
Percentage of  Percentage of  Percentage of 
beneficiaries  beneficiaries  hospitalized 
hospitalized with  hospitalized with  beneficiaries with 
COVID-19 receiving care  COVID-19 receiving  COVID-19 receiving 
in ICU  mechanical ventilation  mechanical ventilation 
outside ICU 
Detroit  50%  23%  6% 
Houston  50%  21%  4% 
Miami  57%  18%  8% 
New Orleans  38%  25%  8% 
New York City  26%  23%  31% 
Phoenix  71%  20%  2% 
Average  49%  22%  10% 
Source: OIG analysis of Medicare data, 2021. 
 
Data Brief: Medicare Beneficiaries Hospitalized With COVID-19 Experienced a Wide Range of Serious, Complex Conditions 
OEI-02-20-00410  Appendix E | 21   
AAPPPPEENNDDIIXX  DF  
 
Characteristics of Medicare Beneficiaries Hospitalized With 
COVID-19 in Six Selected Localities During a Surge 
Exhibit F-1: Percentage of Medicare beneficiaries by eligibility status 
 
  Dually eligible  Medicare only 
Detroit  Hospitalized with COVID-19  43%  57% 
  Total Medicare Population  16%  81% 
Houston  Hospitalized with COVID-19  36%  64% 
  Total Medicare Population  15%  82% 
Miami  Hospitalized with COVID-19  58%  42% 
  Total Medicare Population  29%  69% 
New Orleans  Hospitalized with COVID-19  51%  49% 
  Total Medicare Population  23%  74% 
New York City  Hospitalized with COVID-19  52%  48% 
  Total Medicare Population  23%  73% 
Phoenix  Hospitalized with COVID-19  39%  61% 
  Total Medicare Population  15%  82% 
Average  Hospitalized with COVID-19  47%  53% 
  Total Medicare Population  20%  77% 
Note: The numbers presented in the table do not sum to 100 percent because some beneficiaries were missing 
information about eligibility status. 
Source: OIG analysis of Medicare data, 2021.  
 
   
Data Brief: Medicare Beneficiaries Hospitalized With COVID-19 Experienced a Wide Range of Serious, Complex Conditions 
OEI-02-20-00410  Appendix F | 22  Exhibit F-2: Percentage of Medicare beneficiaries by race and ethnicity 
 
  Asian/  Black/  Hispanic  White 
Pacific  African 
Islander  American 
Detroit  Hospitalized with COVID-19  2%  55%  1%  40% 
  Total Medicare Population  1%  21%  0%  73% 
Houston  Hospitalized with COVID-19  3%  26%  35%  33% 
  Total Medicare Population  5%  18%  7%  64% 
Miami  Hospitalized with COVID-19  1%  23%  45%  26% 
  Total Medicare Population  1%  15%  16%  61% 
New Orleans  Hospitalized with COVID-19  1%  59%  4%  35% 
  Total Medicare Population  1%  33%  1%  62% 
New York City  Hospitalized with COVID-19  6%  26%  23%  41% 
  Total Medicare Population  6%  16%  7%  63% 
Phoenix  Hospitalized with COVID-19  2%  6%  28%  55% 
  Total Medicare Population  2%  5%  4%  84% 
Average  Hospitalized with COVID-19  2%  33%  23%  38% 
  Total Medicare Population  3%  18%  6%  68% 
Notes: The numbers presented in the table do not sum to 100 percent because 4 percent of beneficiaries hospitalized 
with COVID-19 were identified as American Indian/Alaska Native, Other, Unknown, or had missing race and ethnicity 
data.  Information for these beneficiaries is not included in the table because of limitations with the data.  
Furthermore, although Hispanic is an ethnicity, Medicares data combine race and ethnicity and limit beneficiaries to 
one category. 
Source: OIG analysis of Medicare data, 2021. 
Exhibit F-3: Percentage of Medicare beneficiaries by age 
 
  Under 65  65 to 74  75 to 84  85 and 
older 
Detroit  Hospitalized with COVID-19  14%  36%  29%  21% 
  Total Medicare Population  18%  48%  24%  10% 
Houston  Hospitalized with COVID-19  17%  40%  28%  15% 
  Total Medicare Population  14%  54%  24%  8% 
Miami  Hospitalized with COVID-19  11%  32%  34%  23% 
  Total Medicare Population  10%  47%  29%  14% 
New Orleans  Hospitalized with COVID-19  13%  33%  31%  22% 
  Total Medicare Population  19%  49%  22%  9% 
New York City  Hospitalized with COVID-19  11%  33%  33%  23% 
  Total Medicare Population  13%  48%  26%  13% 
Phoenix  Hospitalized with COVID-19  16%  38%  31%  15% 
  Total Medicare Population  13%  51%  27%  9% 
Average  Hospitalized with COVID-19  14%  35%  31%  20% 
  Total Medicare Population  15%  50%  25%  11% 
Source: OIG analysis of Medicare data, 2021. 
Data Brief: Medicare Beneficiaries Hospitalized With COVID-19 Experienced a Wide Range of Serious, Complex Conditions 
OEI-02-20-00410  Appendix F | 23  Exhibit F-4: Percentage of Medicare beneficiaries by sex 
 
  Female  Male 
Detroit  Hospitalized with COVID-19  52%  48% 
  Total Medicare Population  55%  45% 
Houston  Hospitalized with COVID-19  48%  52% 
  Total Medicare Population  54%  46% 
Miami  Hospitalized with COVID-19  49%  51% 
  Total Medicare Population  56%  44% 
New Orleans  Hospitalized with COVID-19  52%  48% 
  Total Medicare Population  55%  45% 
New York City  Hospitalized with COVID-19  46%  54% 
  Total Medicare Population  56%  44% 
Phoenix  Hospitalized with COVID-19  48%  52% 
  Total Medicare Population  54%  46% 
Average  Hospitalized with COVID-19  49%  51% 
  Total Medicare Population  55%  45% 
Source: OIG analysis of Medicare data, 2021. 
 
Data Brief: Medicare Beneficiaries Hospitalized With COVID-19 Experienced a Wide Range of Serious, Complex Conditions 
OEI-02-20-00410  Appendix F | 24   
ACKNOWLEDGMENTS AND CONTACT 
 
Acknowledgments 
Meridith Seife, Deputy Regional Inspector General, served as the team leader for this 
study.  Others in the Office of Evaluation and Inspections who conducted the study 
include Hannah Morgan and Michael Reilly.  Office of Evaluation and Inspections staff 
who provided support include Joe Chiarenzelli and Kevin Farber.  
We would also like to acknowledge the contributions of other Office of Inspector 
General staff including Elina Breton, Logan Kingma, Justin Koppa, and Jessica 
Swanstrom. 
This report was prepared under the direction of Jodi Nudelman, Regional Inspector 
General for Evaluation and Inspections in the New York regional office, and Nancy 
Harrison, Deputy Regional Inspector General. 
Contact 
To obtain additional information concerning this report, contact the Office of Public 
Affairs at Public.Affairs@oig.hhs.gov.  OIG reports and other information can be found 
on the OIG website at oig.hhs.gov. 
Office of Inspector General 
U.S. Department of Health and Human Services 
330 Independence Avenue, SW 
Washington, DC 20201 
Data Brief: Medicare Beneficiaries Hospitalized With COVID-19 Experienced a Wide Range of Serious, Complex Conditions 
OEI-02-20-00410  Acknowledgments and Contact | 25   
EENNDDNNOOTTEESS  
 
 
1 CDC, COVID Data Tracker.  Accessed at https://covid.cdc.gov/covid-data-tracker/#datatracker-home on July 29, 2021. 
2 OIG, Hospital Experiences Responding to the COVID-19 Pandemic: Results of a National Pulse Survey March 23-27, 2020, 
OEI-06-20-00300, April 2020.  OIG, Hospitals Reported That the COVID-19 Pandemic Has Significantly Strained Health Care 
Delivery, OEI-09-21-00140, March 2021. 
3 For the purposes of this report, we considered a locality to be a Core-Based Statistical Area (CBSA) as defined by the U.S. 
Office of Management and Budget (OMB).  We based our analysis on 831 CBSAs that each had at least one short-term acute-
care hospital. 
4 Generally, Medicare is available for people age 65 or older, younger people with disabilities and people with End Stage Renal 
Disease (permanent kidney failure requiring dialysis or transplant). For more information, see 
https://www.hhs.gov/answers/medicare-and-medicaid/who-is-elibible-for-medicare/index.html 
5 For additional geospatial applications, Story Maps, and reports, see https://geohub.oig.hhs.gov/. 
6 The full titles of the selected CBSAs are Detroit-Warren-Dearborn, MI; Houston-The Woodlands-Sugar Land, TX; Miami-Fort 
Lauderdale-Pompano Beach, FL; New Orleans-Metairie, LA; New York-Newark-Jersey City, NY-NJ-PA; and Phoenix-Mesa-
Chandler, AZ. 
7 CDC, People with Certain Medical Conditions.  Accessed at https://www.cdc.gov/coronavirus/2019-ncov/need-extra-
precautions/people-with-medical-conditions.html on July 20, 2021. 
8 Note that we did not include all acute or chronic conditions that Medicare beneficiaries with COVID-19 were treated for.  We 
identified certain conditions that were both common and may have been related to the course of disease for COVID-19 or 
related to risk of severe outcomes for COVID-19. 
9 For many conditions, a similar percentage of beneficiaries was diagnosed with that condition across the six localities.  We 
note when there are large differences in the localities. 
10 C. John Sperati, Coronavirus: Kidney Damage Caused by COVID-19.  Accessed at 
https://www.hopkinsmedicine.org/health/conditions-and-diseases/coronavirus/coronavirus-kidney-damage-caused-by-
covid19 on July 20, 2021. 
11 CDC, People with Certain Medical Conditions.  Accessed at https://www.cdc.gov/coronavirus/2019-ncov/need-extra-
precautions/people-with-medical-conditions.html on July 20, 2021.  American Heart Association, Coronavirus precautions for 
patients and others facing higher risks.  Accessed at https://www.heart.org/en/coronavirus/coronavirus-covid-19-
resources/coronavirus-precautions-for-patients-and-others-facing-higher-risks on July 20, 2021. 
12 For the purposes of this report, we refer to diabetes mellitus as diabetes. 
 
13 CDC, People with Certain Medical Conditions.  Accessed at https://www.cdc.gov/coronavirus/2019-ncov/need-extra-
precautions/people-with-medical-conditions.html on July 20, 2021.  American Diabetes Association, How COVID-19 Impacts 
People with Diabetes.  Accessed at https://www.diabetes.org/coronavirus-covid-19/how-coronavirus-impacts-people-with-
diabetes on July 20, 2021.  
14 Length of stay refers to the number of days between the start and end of an inpatient hospital admission.  An admission 
ends with a beneficiarys discharge or death. 
15 Carrie Macmillan, Ventilators and COVID-19: What You Need to Know, Yale Medicine.  Accessed at 
https://www.yalemedicine.org/stories/ventilators-covid-19 on July 20, 2021. 
 
Data Brief: Medicare Beneficiaries Hospitalized With COVID-19 Experienced a Wide Range of Serious, Complex Conditions 
OEI-02-20-00410  Endnotes | 26   
16 In the three localities that faced a surge in April, on average 24 percent of beneficiaries received mechanical ventilation.  In 
the three localities that faced a surge in July, on average 20 percent of beneficiaries received mechanical ventilation.  Physicians 
learned that giving high-flow oxygen and positioning patients in a prone position resulted in better outcomes than mechanical 
ventilation.  For more information, see Alison E. Thompson, Benjamin L. Ranard, Ying Wei, et al., Prone Positioning in Awake, 
Nonintubated Patients With COVID-19 Hypoxemic Respiratory Failure, JAMA Internal Medicine, Vol. 180, No. 11, November 
2020.  Accessed at https://jamanetwork.com/journals/jamainternalmedicine/fullarticle/2767575 on July 20, 2021.  See also 
Columbia University Irving Medical Center, Proning COVID-19 Patients Reduces Need for Ventilators.  Accessed at 
https://www.cuimc.columbia.edu/news/proning-covid-19-patients-reduces-need-ventilators on July 20, 2021. 
17 CDC, Health Equity Considerations and Racial and Ethnic Minority Groups.  Accessed at 
https://www.cdc.gov/coronavirus/2019-ncov/community/health-equity/race-ethnicity.html on July 20, 2021. 
18 Ibid. 
19 CMS, People Dually Eligible for Medicare and Medicaid.  Accessed at https://www.cms.gov/Medicare-Medicaid-
Coordination/Medicare-and-Medicaid-Coordination/Medicare-Medicaid-Coordination-
Office/Downloads/MMCO_Factsheet.pdf on July 20, 2021.  CMS, Medicare-Medicaid Coordination Office FY 2019 Report to 
Congress.  Accessed at https://www.cms.gov/files/document/mmco-report-congress.pdf on July 20, 2021.  Medicare Payment 
Advisory Commission, Data Book: Beneficiaries Dually Eligible for Medicare and MedicaidJanuary 2018, p. 3.  Accessed at 
http://medpac.gov/docs/default-source/data-book/jan18_medpac_macpac_dualsdatabook_sec.pdf on July 20, 2021. 
20 CMS, Preliminary Medicare COVID-19 Data Snapshot.  Accessed at https://www.cms.gov/research-statistics-data-
systems/preliminary-medicare-covid-19-data-snapshot on July 20, 2021. 
21 We based our analyses on data from the National Claims History File as of May 11, 2021. 
22 CBSAs are areas defined by OMB based on Census Bureau data.  Each CBSA consists of at least one urbanized area or urban 
cluster with a population of at least 10,000 plus adjacent counties with a high degree of social and economic integration.  See 
Census Bureau, Core-Based Statistical Areas.  Accessed at https://www.census.gov/topics/housing/housing-
patterns/about/core-based-statistical-areas.html on July 20, 2021. 
23 Although hospitals in Maryland are not paid under the Inpatient Prospective Payment System, we included short-term acute-
care hospitals in Maryland in our analysis. 
24 For beneficiaries diagnosed with COVID-19, hospitals add the ICD-10-CM code U07.1 to the claim.  The United States 
adopted this code effective April 1, 2020.  Prior to the addition of this new code, health care providers were instructed to use a 
diagnosis code of B97.29.  See: CDC, ICD-10-CM Official Coding and Reporting Guidelines April 1, 2020 through September 30, 
2020.  Accessed at https://www.cdc.gov/nchs/data/icd/COVID-19-guidelines-final.pdf on July 20, 2021. 
25 We considered all beneficiaries enrolled in Medicare Fee-for-Service or Medicare Advantage in each locality as of April 1, 
2020. 
26 We also considered each localitys geography and the total number of hospitalized Medicare beneficiaries, as well as the 
total Medicare enrollment within each locality. 
27 We used claim-from-date and claim-through-date to calculate the length of each stay.  We excluded outliers from the length 
of stay calculation.  Beneficiaries who had at least 1 day of their hospital stay within the 3-week surge period were included.   
28 Mechanical ventilation is identified by the ICD-10-PCS codes 5A1935Z, 5A1945Z, and 5A1955Z.  We did not consider other 
types of noninvasive respiratory support such as continuous positive airway pressure. 
29 Celia Eicheldinger and Arthur Bonito, More Accurate Racial and Ethnic Codes for Medicare Administrative Data, Health Care 
Financing Review, Vol. 29, No. 3, Spring 2008.  Accessed at https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4195038/pdf/hcfr-
29-03-027.pdf on July 20, 2021. 
 
Data Brief: Medicare Beneficiaries Hospitalized With COVID-19 Experienced a Wide Range of Serious, Complex Conditions 
OEI-02-20-00410  Endnotes | 27   
30 Note that the data combine race and ethnicity and allow for only one response, whereas Federal guidelines recommend 
capturing race and ethnicity data separately and allowing respondents to make multiple selections.  For a fuller discussion 
about the data, please see our forthcoming report, Medicare Data on Race and Ethnicity, OEI-02-21-00100. 
 
Data Brief: Medicare Beneficiaries Hospitalized With COVID-19 Experienced a Wide Range of Serious, Complex Conditions 
OEI-02-20-00410  Endnotes | 28