Coronavirus disease 2019 (COVID-19) is a complex clinical illness with potential complications
that might require ongoing clinical care (
1
–
3
). Few studies have investigated discharge patterns and hospital readmissions among
large groups of patients after an initial COVID-19 hospitalization (
4
–
7
). Using electronic health record and administrative data from the Premier Healthcare
Database,* CDC assessed patterns of hospital discharge, readmission, and demographic
and clinical characteristics associated with hospital readmission after a patient’s
initial COVID-19 hospitalization (index hospitalization). Among 126,137 unique patients
with an index COVID-19 admission during March–July 2020, 15% died during the index
hospitalization. Among the 106,543 (85%) surviving patients, 9% (9,504) were readmitted
to the same hospital within 2 months of discharge through August 2020. More than a
single readmission occurred among 1.6% of patients discharged after the index hospitalization.
Readmissions occurred more often among patients discharged to a skilled nursing facility
(SNF) (15%) or those needing home health care (12%) than among patients discharged
to home or self-care (7%). The odds of hospital readmission increased with age among
persons aged ≥65 years, presence of certain chronic conditions, hospitalization within
the 3 months preceding the index hospitalization, and if discharge from the index
hospitalization was to a SNF or to home with health care assistance. These results
support recent analyses that found chronic conditions to be significantly associated
with hospital readmission (
6
,
7
) and could be explained by the complications of underlying conditions in the presence
of COVID-19 (
8
), COVID-19 sequelae (
3
), or indirect effects of the COVID-19 pandemic (
9
). Understanding the frequency of, and risk factors for, readmission can inform clinical
practice, discharge disposition decisions, and public health priorities such as health
care planning to ensure availability of resources needed for acute and follow-up care
of COVID-19 patients. With the recent increases in cases nationwide, hospital planning
can account for these increasing numbers along with the potential for at least 9%
of patients to be readmitted, requiring additional beds and resources.
Data for this study were obtained from the Premier Healthcare Database, which includes
discharge records from 865 nongovernmental, community, and teaching hospitals that
contributed inpatient data during the study period. COVID-19 patients were identified
through International Classification of Diseases, Tenth Revision, Clinical Modification
(ICD-10-CM) discharge diagnosis code of U07.1 (COVID-19, virus identified) during
April–July 2020 or B97.29 (Other coronavirus as the cause of disease classified elsewhere
[recommended before the April 2020 release of U07.1]
†
) during March–April 2020. Both codes were used for discharges during April. The patient’s
first hospitalization with a COVID-19 discharge diagnosis was defined as the index
hospitalization. Any subsequent hospitalization occurring within 2 months of the index
hospitalization discharge date through August 2020, whether for COVID-19 or other
health complications, was considered a hospital readmission.
§
Hospital readmissions that occurred >2 months after the index hospitalization were
excluded. In the Premier Healthcare Database, readmissions were only recorded if a
patient returned to the same hospital where the index hospitalization occurred.
Demographic and clinical characteristics of patients at their index hospitalization
were compared regarding discharge disposition and readmission status (none versus
one or more). Presence of selected chronic conditions associated with a more severe
COVID-19 clinical course were identified through ICD-10-CM diagnosis codes during
or before the index COVID-19 hospitalization. Visits before the index hospitalization
included all inpatient encounters for the cohort during calendar year 2020 only. Five
chronic conditions that have been identified by CDC to increase or possibly increase
the risk for severe COVID-19–associated illness (chronic obstructive pulmonary disease,
heart failure, diabetes [type 1 or type 2, with chronic complications], chronic kidney
disease, and obesity [body mass index ≥30 kg/m2], including severe obesity, [body
mass index ≥40 kg/m2]) were mapped to ICD-10-CM codes using the Elixhauser Comorbidity
Index (a method for classifying comorbidities based on ICD diagnosis codes found in
administrative data; each comorbidity category is dichotomous [present or absent])
and implemented with the Elixhauser Comorbidity Software for ICD-10-CM (beta version;
Agency for Healthcare Research and Quality) and R software (version 4.0.92020; The
R Foundation)
¶
(
10
). The following three clinical severity indicators were defined using hospital chargemaster
records (i.e., the comprehensive list of all items billable to a hospital patient
or to a patient’s insurance provider): intensive care unit (ICU) admission, invasive
mechanical ventilation, and noninvasive ventilation. Time to readmission after the
index hospitalization was calculated as the difference in days between date of readmission
and date of discharge from the previous hospitalization. The primary discharge diagnosis
for each hospitalization was categorized into Clinical Classification Software Refined
Categories to approximate the primary reason for the hospital stay. A multivariable
generalized estimating equation model assessed the odds of readmission, accounting
for within-facility correlation. Covariates included in the model were age, sex, race/ethnicity,
presence of selected chronic conditions, discharge disposition category, and clinical
severity indicators. This activity was reviewed by CDC and was conducted consistent
with applicable federal law and CDC policy.**
During March–July 2020, a total of 126,137 patients within the Premier Healthcare
Database were hospitalized for COVID-19. The majority of patients were admitted from
a non–health care setting (81%), followed by transfer from another hospital, clinic,
or SNF (18%) (Table 1). During the index hospitalization, 15% of patients were admitted
to an ICU, 13% required invasive mechanical ventilation, and 4% required noninvasive
ventilation. At the time of the index hospitalization or at any time during 2020 before
the hospitalization, 62% of patients had an ICD-10-CM diagnosis code for one or more
of the following five chronic conditions: chronic obstructive pulmonary disease (21%),
heart failure (16%), diabetes mellitus type 1 or type 2 (27%), chronic kidney disease
(21%), or obesity (27%). Overall, 10,008 (8%) patients had been hospitalized at the
same hospital in the 3 months preceding their index COVID-19 hospitalization. Approximately
15% of patients (19,594) died during the index hospitalization.
TABLE 1
Demographic characteristics of hospitalized COVID-19 patients at index hospitalization,
by readmission status — Premier Healthcare Database, United States, March–August 2020
Characteristic
No. (%)
Total
Not readmitted
Readmitted at least once
N = 126,137
N = 116,633
N = 9,504
Age group (yrs)
<18
1,170 (0.9)
1,095 (0.9)
75 (0.8)
18–39
16,699 (13.2)
15,741 (13.5)
958 (10.1)
40–49
14,490 (11.5)
13,674 (11.7)
816 (8.6)
50–64
35,451 (28.1)
32,923 (28.2)
2,528 (26.6)
65–74
25,419 (20.2)
23,250 (19.9)
2,169 (22.8)
75–84
19,864 (15.7)
18,061 (15.5)
1,803 (19.0)
≥85
13,044 (10.3)
11,889 (10.2)
1,155 (12.2)
Race/Ethnicity
Asian, non-Hispanic
3,652 (2.9)
3,429 (2.9)
223 (2.4)
Black, non-Hispanic
29,226 (23.2)
26,819 (23.0)
2,407 (25.3)
Hispanic
26,921 (21.3)
25,412 (21.8)
1,509 (15.9)
White, non-Hispanic
49,133 (39.0)
44,807 (38.4)
4,326 (45.5)
Other
13,048 (10.3)
12,194 (10.5)
854 (9.0)
Sex
Female
60,426 (47.9)
55,827 (47.9)
4,599 (48.4)
Male
65,597 (52.0)
60,695 (52.0)
4,902 (51.6)
Unknown
114 (0.1)
111 (0.1)
—*
Point of origin
Non–health care
102,482 (81.2)
94,796 (81.3)
7,686 (74.5)
Clinic
6,787 (5.4)
6,217 (5.3)
570 (5.5)
Transfer from a different hospital
8,425 (6.7)
7,968 (6.8)
457 (4.4)
Transfer from SNF or ICF
5,940 (4.7)
5,324 (4.6)
616 (6.0)
Transfer from health facility
1,437 (1.1)
1,339 (1.1)
98 (1.0)
Court/Law enforcement
252 (0.2)
241 (0.2)
11 (0.1)
Born inside the hospital
45 (0.0)
44 (0.0)
—*
Not available
441 (0.3)
410 (0.4)
31 (0.3)
U.S. Census division
East North Central
16,009 (12.7)
14,547 (12.5)
1,462 (15.4)
East South Central
5,986 (4.7)
5,544 (4.8)
442 (4.7)
Middle Atlantic
39,673 (31.5)
36,456 (31.3)
3,217 (33.9)
Mountain
8,852 (7.0)
8,355 (7.2)
497 (5.2)
New England
3,768 (3.0)
3,346 (2.9)
422 (4.4)
Pacific
6,511 (5.2)
6,138 (5.3)
373 (3.9)
South Atlantic
27,407 (21.7)
25,683 (22.0)
1,724 (18.1)
West North Central
4,364 (3.5)
3,998 (3.4)
366 (3.9)
West South Central
13,567 (10.8)
12,566 (10.8)
1,001 (10.5)
Abbreviations: COVID-19 = coronavirus disease 2019; ICF = intermediate care facility;
SNF = skilled nursing facility.
* Cell sizes <10 were suppressed.
Among the 106,543 patients discharged from the index admission, 9,504 (9%) were readmitted,
including 1,667 (1.6%) who were readmitted more than once. The median interval from
discharge to first readmission was 8 days (interquartile range = 3–20 days). Less
than 0.1% of patients died during readmission (data suppressed for privacy).
Among all patients who were discharged after the index hospitalization, 60% were discharged
to home or self-care (to home without any additional professional services provided
such as home nursing health care), 15% to a SNF, 10% to home with assistance from
a home health organization, 4% to hospice, 4% to ongoing care, and 5% to other locations
(Table 2). Readmission was more common among patients discharged to a SNF (15%) or
with home health organization support (12%), compared with patients discharged to
home or self-care (7%). Median age, severity markers, time to readmission and length
of stay differed by index hospitalization discharge disposition category.
TABLE 2
Discharge status and subsequent readmissions among 126,137 COVID-19 patients* with
an index hospitalization — United States, March–August 2020
Characteristic
Location to which patient was discharged from index hospitalization
Home or self-care
SNF
Home health organization
Hospice
Ongoing care†
Other§
Discharged (N = 106,543 [85%])
No. of patients discharged, (%)
64,475 (60)
16,339 (15)
12,223 (10)
3,807 (4)
4,404 (4)
5,295 (5)
Length of index hospitalization, days, median (IQR)
4 (2–7)
8 (5–15)
8 (4–14)
7 (4–12)
16 (7–29)
3 (1–7)
Male, %
51
47
49
47
57
61
Median age, yrs
53
76
68
83
66
61
≥1 chronic condition, %
53
72
70
67
70
57
ICU admission, %
35
42
45
53
63
42
Readmitted (N = 9,504, 9%)
¶
No. (%) of patients readmitted
4,406 (7)
2,517 (15)
1,469 (12)
136 (4)
494 (11)
482 (9)
No. days to readmission, median (IQR)
7 (3–17)
11 (5–25)
8 (3–19)
0 (0–3)
10 (3–25)
6 (1–21)
Length of hospitalization, days, median (IQR)
4 (2–7)
6 (3–9)
5 (3–8)
3 (1–6)
6 (3–10)
4 (2–8)
Male, %
51
50
49
51
62
64
Median age, yrs
58
75
72
80
67
59
≥1 chronic condition, %
67
80
80
75
77
67
Abbreviations: COVID-19 = coronavirus disease 2019; ICU = intensive care unit; IQR
= interquartile range; SNF = skilled nursing facility.
* A total of 19,594 (15%) patients died during the index hospitalization; 59% of decedents
were male, median age was 74 years, 75% had one or more chronic conditions, the median
hospitalization duration was 8 days (IQR = 4–15 days), and 68% of patients were admitted
to an ICU.
† Ongoing care categories include discharged/transferred to cancer center, admitted
as an inpatient to this hospital, still a patient, discharged/transferred to federal
hospital, discharged/transferred to swing bed unit (a unit within an acute care hospital
where patients receive the same skilled level of care that is available at skilled
nursing facilities), discharged/transferred to another rehabilitation facility, discharged/transferred
to long-term care hospitals that provide acute inpatient care with an average length
of stay of ≥25 days, discharged to a psychiatric hospital, discharged/transferred
to a critical access hospital.
§ Other category includes patients who were discharged to other facilities and those
who left against medical advice.
¶ Readmitted from discharged location noted in column (after index hospitalization).
When controlling for covariates, the odds of readmission increased with the presence
of chronic obstructive pulmonary disease (OR = 1.4), heart failure (OR = 1.6), diabetes
(OR = 1.2), and chronic kidney disease (OR = 1.6). Patients were more likely to be
readmitted if they had been discharged from the index hospitalization to a SNF (OR
= 1.4) or with home health organization support (OR = 1.3) than if they had been discharged
to home or self-care. Compared with persons aged 18–39 years, the odds of readmission
increased with age among persons aged ≥65 years (Table 3). Adjusted odds of readmission
of patients with a hospitalization in the 3 months preceding their index hospitalization
were 2.6 times the odds of those who were not hospitalized in the preceding 3 months.
Non-Hispanic White persons were more likely to be readmitted than were those of other
racial/ethnic groups. Common primary discharge diagnoses after readmission were infectious
and parasitic diseases (primarily COVID-19; 45%) and diseases of the circulatory (11%)
and digestive (7%) systems (Supplementary Table, https://stacks.cdc.gov/view/cdc/96391).
TABLE 3
Generalized estimating equation model showing the adjusted odds of readmission among
persons hospitalized with COVID-19 — United States, March–August 2020
Characteristic
Odds ratio (95%CI)
Standard error*
P-value
Age group (yrs), (referent = 18–39 yrs)
<18
1.03 (0.80–1.33)
0.13
0.806
40–49
0.94 (0.84–1.04)
0.05
0.204
50–64
1.08 (0.99–1.17)
0.04
0.078
65–74
1.22 (1.12–1.34)
0.05
<0.001
75–84
1.32 (1.20–1.46)
0.05
<0.001
≥85
1.37 (1.23–1.53)
0.06
<0.001
Race/Ethnicity (referent = White, non-Hispanic)
Asian, non-Hispanic
0.82 (0.71–0.95)
0.07
0.007
Black, non-Hispanic
0.90 (0.85–0.95)
0.03
<0.001
Hispanic
0.75 (0.71–0.81)
0.03
<0.001
Other
0.80 (0.74–0.87)
0.04
<0.001
Sex (referent = male)
Female
0.94 (0.90–0.99)
0.02
0.015
Chronic conditions
COPD
1.35 (1.28–1.42)
0.03
<0.001
Heart failure
1.58 (1.48–1.67)
0.03
<0.001
Diabetes
1.21 (1.14–1.28)
0.03
<0.001
Chronic kidney disease
1.64 (1.55–1.74)
0.03
<0.001
Obesity
0.95 (0.90–1.00)
0.03
0.049
Previous hospitalization† (yes versus no)
2.61 (2.45–2.78)
0.03
<0.001
Severity measures at index hospitalization
Length of stay, days
0.99 (0.99–1.00)
0.00
0.001
ICU admission
0.94 (0.89–0.99)
0.03
0.014
Mechanical ventilation
1.15 (1.04–1.27)
0.05
0.006
Noninvasive ventilation
0.86 (0.81–0.90)
0.03
<0.001
Discharge category from index hospitalization (referent = home/self-care)
SNF
1.37 (1.29–1.47)
0.03
<0.001
Home health organization
1.30 (1.21–1.39)
0.04
<0.001
Hospice
0.24 (0.20–0.29)
0.09
<0.001
Ongoing care
1.22 (1.09–1.36)
0.06
0.001
Abbreviations: CI = confidence interval; COPD = chronic obstructive pulmonary disease;
COVID-19 = coronavirus disease 2019; ICU = intensive care unit; SNF = skilled nursing
facility.
* Standard error of coefficient.
† Patients who had a hospitalization within 3 months before their COVID-19 index hospitalization.
Discussion
In a cohort of 106,543 patients discharged after an index COVID-19 hospitalization,
9% experienced at least one readmission to the same hospital within 2 months of discharge.
More than one readmission occurred in 1.6% of cases. In this analysis, the odds of
hospital readmission increased with age among persons aged ≥65 years, presence of
one of five selected chronic conditions, hospitalization within the 3 months preceding
the index hospitalization, and if discharge from the index hospitalization was to
a SNF or to home with health care assistance. Although the proportions of patients
in the Premier Healthcare Database cohort who were non-Hispanic Black (23%) or Hispanic
(21%) were higher than those proportions in the U.S. Census (13% and 18%, respectively),
their odds of readmission were lower than those of non-Hispanic White patients. The
slight association of readmission with lengths of stay for hospitalized COVID-19 patients
merits further study.
These results are comparable to those of recently published analyses, which found
a similar group of chronic conditions to be significantly associated with hospital
readmission (
6
,
7
) and could be explained by the complications of underlying conditions in the presence
of COVID-19 (
8
), COVID-19 sequelae (
3
), or indirect effects of the COVID-19 pandemic (
9
). Although only a small proportion of patients discharged to home or self-care were
readmitted, 7% returned to the hospital within a median of 7 days. One explanation
for their readmission is that approximately two thirds of these 4,406 patients had
one or more of the selected chronic conditions.
After hospitalization for COVID-19, the most common primary discharge diagnoses from
hospital readmission were diseases of the circulatory, digestive, or respiratory systems.
Future work will examine the detailed diagnoses recorded during readmissions to better
understand COVID-19 sequelae or health conditions that require extended or ongoing
care.
The findings in this report are subject to at least five limitations. First, COVID-19
diagnoses were determined by ICD-10-CM, not through laboratory confirmation, potentially
leading to misclassification of cases. Second, chronic conditions were identified
using ICD-10-CM diagnostic codes used at the index hospitalization or a previous encounter.
If a patient had a chronic condition but the condition was not assigned a diagnostic
code, that condition would not be recorded in this analysis. Third, primary discharge
diagnosis was used to infer the primary reason for hospital admission; other diagnoses
might have contributed to the reason for index admission and readmissions. Fourth,
patients who received care at different hospitals would not be assessed longitudinally.
Finally, the sequelae of COVID-19 could not be completely described among hospitalized
patients or among those readmitted. Sequelae might be experienced by patients who
are never readmitted to a hospital.
Information on the frequency of, and risk factors for, readmission can inform clinical
practice and discharge disposition decisions especially with regard to the acuity
and location of ongoing care needed for persons who might appear stable at discharge.
Further, addressing priorities such as health care planning to ensure adequate health
care resources for acute and post-acute follow-up care of COVID-19 patients is critical
at a local, regional, and national level. With the recent increase in cases nationwide,
hospital planning can account for these increasing numbers along with the potential
for at least 9% of patients to be readmitted, requiring additional beds and resources.
Continued public health messaging and interventions to prevent COVID-19 among older
persons and those with underlying medical conditions is essential.
Summary
What is already known about this topic?
Evidence suggests that potential health complications after COVID-19 illness might
require ongoing clinical care.
What is added by this report?
After discharge from an initial COVID-19 hospitalization, 9% of patients were readmitted
to the same hospital within 2 months of discharge. Multiple readmissions occurred
in 1.6% of patients. Risk factors for readmission included age ≥65 years, presence
of certain chronic conditions, hospitalization within the 3 months preceding the first
COVID-19 hospitalization, and discharge to a skilled nursing facility or with home
health care.
What are the implications for public health practice?
Understanding frequency of, and potential reasons for, readmission after a COVID-19
hospitalization can inform clinical practice, discharge disposition decisions, and
public health priorities, such as health care resource planning.