The emergency department (ED) is often where atrial fibrillation (AF) is first detected and acutely treated and affected patients dispositioned. We used the Nationwide Emergency Department Sample to estimate the percentage of visits resulting in hospitalization and investigate associations between patient and hospital characteristics with hospitalization at the national and regional levels. We conducted a cross-sectional study of adults with AF listed as the primary ED diagnosis in the 2007 to 2009 Nationwide Emergency Department Sample. We performed multivariate logistic regression analyses investigating the associations between prespecified patient and hospital characteristics with hospitalization. From 2007 to 2009, there were 1,320,123 weighted ED visits for AF, with 69% hospitalized nationally. Mean regional hospitalization proportions were: Northeast (74%), Midwest (68%), South (74%), and West (57%). The highest odds ratios for predicting hospitalization were heart failure (3.85, 95% confidence interval [CI] 3.66 to 4.02), chronic obstructive pulmonary disease (2.47, 95% CI 2.34 to 2.61), and coronary artery disease (1.65, 95% CI 1.58 to 1.73). After adjusting for age, privately insured (0.77, 95% CI 0.73 to 0.81) and self-pay (0.77 95% CI 0.66 to 0.90) patients had lower odds compared with Medicare recipients, whereas Medicaid (1.21, 95% CI 1.11 to 1.32) patients tended to have higher odds. Patients living in low-income zip codes (1.18, 95% CI 1.12 to 1.25) and patients treated at large metropolitan hospitals (1.75, 95% CI 1.59 to 1.93) had higher odds. In conclusion, our analysis showed considerable regional variation in the management of patients with AF in the ED and in associations between patient socioeconomic and hospital characteristics with ED disposition; adapting best practices from among these variations in management could reduce hospitalizations and health-care expenses.
Atrial fibrillation (AF) affects from 3 to 6 million Americans, with estimated national incremental health-care costs ranging from $6 to $26 billion per year. The emergency department (ED) is often where AF is first detected and acutely treated and affected patients dispositioned. ED visits for AF increased by 88% from 1993 to 2004, with 64% of these visits resulting in hospitalization. Understanding factors that influence hospitalization may result in more informed acute AF management. Specifically, our health-care system may benefit from a greater knowledge of how health-care disparities impact the significant United States (US) regional variation in hospitalizations for AF. The frequency of ED visits for AF, national and regional AF hospitalizations, and ED cardioversions have not been studied after the publication of the 2006 American College of Cardiology/American Heart Association/European Society of Cardiology guidelines. We used the Nationwide Emergency Department Sample (NEDS) to investigate age-specific ED visit rates for AF, percentage of ED visits resulting in hospitalization, as well as associations between specific patient and hospital characteristics with hospitalization at the national and regional levels.
Methods
NEDS is a US administrative database maintained by the Agency for Healthcare Research and Quality as a component of the Healthcare Cost and Utilization Project. NEDS contains data from 25 to 30 million unweighted hospital-based ED visits annually, representing about 20% of all US visits. NEDS includes data from approximately 29 states and stratifies the data by geographic region (Northeast, Midwest, South, and West), trauma center designation, urban-rural status, teaching hospital status, and ownership. The NEDS database includes weights for calculating national estimates from the 20% sample of measured ED visits. NEDS consists of 4 files: (1) a core file including demographic, diagnostic, ED charges, and disposition data, (2) a supplemental ED file with ED procedures, (3) an inpatient file with hospital procedures for those admitted, and (4) a hospital file describing the characteristics of the hospital-based ED. For each ED encounter, NEDS reports ≤15 diagnoses coded according to their respective International Classification of Diseases (ICD)-9 codes. NEDS also classifies each ICD-9 diagnosis as a nonchronic or chronic condition based on a validated algorithm.
We conducted a cross-sectional study of adults with AF, identified by the ICD-9 code 427.31 listed as the primary ED diagnosis from 2007 to 2009. We limited our analysis to the 3 years after publication of the 2006 American College of Cardiology/American Heart Association/European Society of Cardiology guidelines for the Management of Patients with AF. All outcomes referring to hospitalizations included visits in which the patient was admitted to the same hospital or transferred to a short-term acute care hospital. We calculated annual incidences of ED visits for AF from 2007 to 2009, percentages of ED visits for AF resulting in hospitalization, and the percentage of visits associated with ED or inpatient electrical cardioversions. We further stratified these incidences by US geographic region and age groups defined by the US census. We documented ED cardioversion frequencies to determine whether regional variation in hospitalization may be explained by increased frequency of ED cardioversion in the regions with lower hospitalization percentages. Electrical cardioversions performed in the ED and inpatient settings were measured using specific Current Procedural Terminology codes 92960 and 92961 in the ED procedures section and Clinical Classifications Software code 225 in the inpatient procedures section.
National and regional estimates of frequencies and percentages, and all regression analyses, accounted for the NEDS sampling design. Age-specific annual incidences of ED visits for AF were calculated by dividing the weighted annual number of ED visits for AF by July population estimates from the US Census Bureau, then expressing this quantity as ED visits per 1,000 persons. Two multivariate logistic regression analyses were used to investigate the association between a priori selected patient and hospital characteristics with hospitalization. The models evaluated associations between these independent variables, including US geographic region as an independent variable, and hospitalization from the ED at the national level stratified by region. The Supplementary Table 1 provides a detailed description of the independent variables. We chose these patient and hospital characteristics based on our previous investigations, an extensive review of the medical works, and our clinical experience. This study was conducted with de-identified data and was approved by the local institutional review board as nonhuman research. All analyses were done using the statistical programming language SAS software, version 9.2 of the SAS System for Linux (Cary, North Carolina).
Results
From 2007 to 2009, there were 376,162,043 (95% confidence interval [CI] 362,625,877 to 389,698,208) total weighted ED visits including 1,320,123 (95% CI 1,258,776 to 1,381,471) weighted ED visits for AF. Table 1 lists the characteristics for the ED visits for AF overall including regional hospitalization frequencies. Characteristics stratified by census age groups are listed in Table 2 . Figure 1 shows what appears to be a consistent trend in all 4 US geographic regions, with greater hospitalization percentages associated with increasing patient age. The percentage of patients with AF who underwent ED electrical cardioversion nationwide during 2007 to 2009 was 3.5% (95% CI 2.9 to 4.1). Regional percentages of ED cardioversion were Northeast 4.3% (95% CI 3.2 to 5.5), Midwest 4.0% (95% CI 2.5 to 5.5), South 1.0% (95% CI 0.7 to 1.2), and West 5.6% (95% CI 4.1 to 7.1). Electrical cardioversions were most frequently performed in the youngest adults ( Figure 2 ) and in the inpatient setting, with reported frequencies of 9.4% (95% CI 8.8 to 10) in 2007, 9.5% (95% CI 8.8 to 10.2) in 2008, and 10.1% (95% CI 9.4 to 10.8) in 2009. There was less regional variation in the performance of inpatient cardioversions ( Supplementary Table 2 —online only).
| Characteristic | 2007 (Nonweighted ED Visits for AF, n = 89,056) | 2008 (Nonweighted ED Visits for AF, n = 101,211) | 2009 (Nonweighted ED Visits for AF, n = 102,979) |
|---|---|---|---|
| Overall weighted ED visits for AF (95% CI) | 411,406 (381,029–441,783) | 445,924 (412,503–479,345) | 462,794 (429,160–496,427) |
| ED visits for AF per 1,000 person-yrs, % ∗ | 1.8 (1.6–2.0) | 1.9 (1.7–2.2) | 2.0 (1.8–2.2) |
| Northeast | 85,834 (20.9) | 88,987 (20.0) | 90,547 (19.6) |
| Midwest | 100,160 (24.4) | 103,923 (23.3) | 111,942 (24.2) |
| South | 154,313 (37.5) | 166,748 (37.4) | 172,070 (37.2) |
| West | 71,098 (17.3) | 86,267 (19.4) | 88,235 (19.1) |
| Age (yrs) ∗ | 69.2 (68.9–69.4) | 69.4 (69.2–69.7) | 69.5 (69.3–69.8) |
| Women | 215,406 (52.4) | 233,940 (52.5) | 243,443 (52.6) |
| ED disposition | |||
| Treated and released | 119,836 (29.1) | 138,045 (31.0) | 141,679 (30.6) |
| Admitted to same hospital | 275,663 (67.0) | 291,822 (65.4) | 306,495 (66.2) |
| Transferred to short-term hospital | 12,563 (3.1) | 14,731 (3.3) | 13,636 (3.0) |
| Died in ED | 152.48 (0.04) | 243.91 (0.05) | 292.95 (0.06) |
| Died in hospital | 2,981 (0.7) | 3,092 (0.7) | 3,166 (0.7) |
| Regional hospitalization, % (95% CI) | |||
| Northeast | 74.2 (71.3–77.2) | 73.6 (70.4–76.8) | 74.5 (71.4–77.6) |
| Midwest | 67.5 (65.2–70.0) | 65.7 (63.3–68.0) | 70.2 (67.9–72.4) |
| South | 74.1 (72.1–76.0) | 73.7 (71.8–75.7) | 73.5 (71.7–75.2) |
| West | 59.9 (56.5–63.2) | 57.9 (54.4–61.4) | 54.1 (49.7–58.5) |
| Length of stay (days) ∗ | 3.7 (3.6–3.7) | 3.7 (3.7–3.8) | 3.7 (3.6–3.7) |
| ED cardioversion | 3,929 (2.9) | 5,374 (3.5) | 6,368 (4.1) |
| Inpatient cardioversion | 25,855 (9.4) | 27,838 (9.5) | 30,852 (10.1) |
| Total ED charge ($) ∗ | 1,892 (1,803–1,980) | 2,169 (2,061–2,276) | 2,437 (2,334–2,540) |
| Total combined ED and inpatient charge ($) ∗ | 21,771 (20,712–22,828) | 23,667 (22,406–24,927) | 24,752 (23,635–25,869) |
| Weekend ED visit | 103,331 (25.2) | 112,360 (25.2) | 115,567 (25.0) |
| Hypertension † | 145,815 (35.4) | 160,797 (36.1) | 167,623 (36.2) |
| Diabetes † | 44,476 (10.8) | 50,835 (11.4) | 52,930 (11.4) |
| Coronary artery disease † | 60,409 (14.7) | 68,173 (15.3) | 68,426 (14.8) |
| Chronic obstructive pulmonary disease † | 40,501 (9.8) | 33,220 (7.5) | 34,344 (7.4) |
| Heart failure † | 70,589 (17.2) | 72,452 (16.3) | 82,929 (17.9) |
| Insurance type, % (95% CI) | |||
| Medicare | 66.2 (65.2–37.1) | 66.7 (65.8–67.7) | 66.7 (65.7–67.7) |
| Medicaid | 4.0 (3.6–4.3) | 4.3 (3.9–4.7) | 4.7 (4.3–5.2) |
| Private, including HMO | 24.0 (23.2–24.8) | 23.3 (22.5–24.2) | 22.8 (22.1–23.6) |
| Self-pay | 3.7 (3.3–4.0) | 3.3 (3.0–3.6) | 3.5 (3.2–3.8) |
| No charge | 0.4 (0.2–0.6) | 0.4 (0.2–0.5) | 0.4 (0.2–0.6) |
| Other | 1.9 (1.6–2.2) | 2.0 (1.7–2.3) | 1.9 (1.6–2.1) |
| Low income | 98,359 (24.4) | 102,227 (23.5) | 105,674 (23.4) |
| Large metropolitan | 179,112 (48.9) | 189,144 (47.7) | 197,803 (48.0) |
| Teaching hospital | 145,749 (35.4) | 149,259 (33.5) | 158,999 (34.4) |
| Safety net hospital | 185,127 (45.0) | 213,410 (47.9) | 241,649 (52.2) |
∗ Data are reported as mean with (95% CI).
† Frequencies of documented chronic disease are reported as weighted frequency (%).
| Characteristic | Age (yrs) | |||||
|---|---|---|---|---|---|---|
| 18–39 | 40–64 | 65–74 | 75–84 | >85 | Overall | |
| Overall weighted ED visits for AF | 0.04 (0.04–0.04) | 0.4 (0.4–0.4) | 1.2 (1.2–1.3) | 1.5 (1.5–1.5) | 1.4 (1.4–1.4) | 0.4 (0.3–0.4) |
| Women | 20.5 (19.6–21.5) | 36.0 (35.5–36.5) | 52.5 (51.9–53.1) | 63.6 (63.1–64.1) | 73.4 (72.8–74.0) | 52.5 (52.2–52.8) |
| ED disposition | ||||||
| Discharged | 44.2 (42.4–45.9) | 35.8 (34.6–37.0) | 31.2 (30.1–32.3) | 26.4 (25.4–27.4) | 21.3 (20.4–22.2) | 30.3 (29.3–31.3) |
| Admitted to same hospital | 52.3 (50.5–54.0) | 60.9 (59.7–62.2) | 64.9 (63.7–66.2) | 70.0 (68.8–71.2) | 75.4 (74.3–76.4) | 66.2 (65.1–67.3) |
| Transferred to short-term hospital | 3.0 (2.6–3.4) | 27.8 (2.5–3.1) | 3.5 (3.0–4.0) | 3.2 (2.8–3.7) | 2.9 (2.5–3.4) | 3.1 (2.7–3.5) |
| Died in ED | 0.02 (0–0.04) | 0.03 (0.02–0.05) | 0.04 (.02–0.06) | 0.06 (0.04–0.07) | 0.1 (0.1–0.1) | 0.05 (0.04–0.06) |
| Medicare | 3.7 (3.2–4.2) | 12.8 (12.4–13.2) | 83.0 (82.3–83.8) | 91.5 (90.9–92.1) | 93.6 (93.0–94.2) | 62.8 (62.1–63.5) |
| Medicaid | 11.6 (10.7–12.5) | 9.4 (8.9–9.9) | 1.6 (1.3–1.8) | 1.0 (0.8–1.2) | 0.6 (0.5–0.7) | 4.0 (3.8–4.3) |
| Private, including HMO | 62.1 (60.6–63.6) | 63.5 (62.4–64.6) | 13.6 (12.9–14.3) | 6.2 (5.7–6.8) | 4.7 (4.2–5.2) | 27.1 (26.4–27.7) |
| Self-pay | 17.5 (16.3–18.6) | 8.9 (8.4–9.4) | 0.9 (0.8–1.1) | 0.6 (0.5–0.7) | 0.5 (0.3–0.6) | 3.8 (3.6–4.1) |
| No charge | 0.9 (0.6–1.3) | 0.9 (0.6–1.2) | 0.1 (0.03–0.1) | 0.04 (0.01–0.06) | 0.03 (0.01–0.04) | 0.3 (0.2–0.5) |
| Other | 4.3 (3.7–4.9) | 4.5 (4.0–4.9) | 0.8 (0.7–1.0) | 0.7 (0.5–0.8) | 0.6 (0.5–0.8) | 2.0 (1.8–2.2) |
| Low income | 25.1 (23.3–26.9) | 24.0 (22.5–25.4) | 24.6 (23.1–26.2) | 23.3 (21.8–24.8) | 22.5 (20.9–24.1) | 23.8 (22.3–25.2) |
| Weekend ED visit | 28.1 (27.2–28.9) | 25.2 (24.9–25.6) | 25.0 (24.7–25.5) | 24.5 (24.2–24.9) | 25.1 (24.6–25.5) | 25.1 (24.9–25.3) |
| Hypertension | 17.2 (16.2–18.1) | 34.9 (34.3–35.5) | 40.2 (39.6–40.9) | 37.6 (36.9–38.2) | 33.5 (32.8–34.2) | 35.9 (35.4–36.4) |
| Diabetes | 3.6 (3.1–4.1) | 12.1 (11.7–12.4) | 13.9 (13.5–14.3) | 11.2 (10.9–11.5) | 7.5 (7.2–7.8) | 11.2 (11.0–11.5) |
| Coronary artery disease | 1.5 (1.3–1.8) | 11.0 (10.6–11.3) | 17.4 (17.0–17.9) | 18.6 (18.2–19.0) | 15.8 (15.3–16.3) | 14.9 (14.6–15.2) |
| Chronic obstructive pulmonary disease | 0.4 (0.3–0.5) | 5.7 (5.5–6.0) | 10.0 (9.7–10.4) | 10.4 (10.1–10.7) | 8.4 (8.0–8.7) | 8.2 (8.0–8.4) |
| Heart failure | 3.6 (3.2–4.0) | 12.0 (11.6–12.4) | 15.0 (14.6–15.5) | 20.3 (19.7–20.8) | 28.2 (27.5–29.0) | 17.1 (16.7–17.5) |
| Large metropolitan | 53.3 (50.6–56.1) | 49.3 (46.9–51.8) | 45.5 (43.1–47.9) | 47.5 (45.1–50.0) | 49.8 (47.2–52.3) | 48.2 (45.8–50.5) |
| Teaching hospital | 40.3 (37.5–43.1) | 37.8 (35.3–40.2) | 32.5 (30.0–34.9) | 32.6 (30.1–35.1) | 32.5 (29.9–35.1) | 34.4 (32.0–36.8) |
| Safety net hospital | 52.0 (48.5–55.5) | 50.5 (47.3–53.7) | 49.7 (46.5–52.9) | 46.7 (43.4–50.0) | 45.0 (41.7–48.4) | 48.5 (45.3–51.7) |
| ED electrical cardioversion performed | 8.0 (6.5–9.4) | 5.4 (4.4–6.4) | 3.0 (2.4–3.6) | 1.6 (1.2–1.9) | 0.7 (0.4–1.0) | 3.5 (2.9–4.1) |
| Inpatient electrical cardioversion performed | 14.2 (13.1–15.3) | 13.1 (12.5–13.8) | 10.7 (10.1–11.3) | 8.2 (7.7–8.7) | 4.6 (4.2–4.9) | 9.7 (9.2–10.1) |
Multivariate analyses found that the Midwest and West regions had lower odds of admission compared with the Northeast ( Table 3 ). The strongest predictors of hospitalization were a history of heart failure, chronic obstructive pulmonary disease, and coronary artery disease. After adjusting for age, privately insured and self-pay patients had lower odds of hospitalization compared with Medicare patients, whereas Medicaid patients tended to have higher odds. Patients living in a low-income zip code and those treated at large metropolitan, safety net, and private investor-owned hospitals had higher odds of hospitalization. We investigated insurance status in patients identified as low income and found that 65% had Medicare, 6% Medicaid, 20% private insurance, 5% self-pay, and 2.5% with no charge or other insurance.
| Characteristic | Region | Adjusted OR (95% CI) | p |
|---|---|---|---|
| Age | National | 1.008 (1.007–1.010) | <0.0001 |
| Northeast | 1.003 (1.00–1.007) | 0.0517 | |
| Midwest | 1.011 (1.009–1.014) | <0.0001 | |
| South | 1.006 (1.003–1.008) | <0.0001 | |
| West | 1.013 (1.010–1.016) | <0.0001 | |
| Women | National | 1.064 (1.040–1.088) | <0.0001 |
| Northeast | 1.101 (1.045–1.160) | 0.0003 | |
| Midwest | 1.035 (0.989–1.083) | 0.1419 | |
| South | 1.057 (1.022–1.093) | 0.0014 | |
| West | 1.072 (1.013–1.133) | 0.0152 | |
| US region | Northeast (ref) | 1.00 | |
| Midwest | 0.762 (0.655–0.886) | 0.0004 | |
| South | 0.846 (0.690–1.036) | 0.1058 | |
| West | 0.44 (0.357–0.543) | <0.0001 | |
| Heart failure | National | 3.845 (3.655–4.017) | <0.0001 |
| Northeast | 6.154 (5.419–6.989) | <0.0001 | |
| Midwest | 3.577 (3.302–3.874) | <0.0001 | |
| South | 3.229 (2.966–3.515) | <0.0001 | |
| West | 3.882 (3.445–4.374) | <0.0001 | |
| Chronic obstructive pulmonary disease | National | 2.469 (2.340–2.605) | <0.0001 |
| Northeast | 3.346 (2.916–3.840) | <0.0001 | |
| Midwest | 2.343 (2.118–2.605) | <0.0001 | |
| South | 2.285 (2.108–2.477) | <0.0001 | |
| West | 2.242 (1.959–2.566) | <0.0001 | |
| Coronary artery disease | National | 1.651 (1.576–1.729) | <0.0001 |
| Northeast | 2.105 (1.850–2.396) | <0.0001 | |
| Midwest | 1.492 (1.374–1.619) | <0.0001 | |
| South | 1.535 (1.420–1.632) | <0.0001 | |
| West | 1.797 (1.581–2.043) | <0.0001 | |
| Hypertension | National | 1.131 (1.094–1.205) | <0.0001 |
| Northeast | 1.437 (1.266–1.630) | <0.0001 | |
| Midwest | 1.105 (1.017–1.200) | 0.0177 | |
| South | 0.943 (0.889–1.001) | 0.0523 | |
| West | 1.263 (1.105–1.443) | 0.00006 | |
| Diabetes | National | 1.147 (1.104–1.193) | <0.0001 |
| Northeast | 1.22 (1.112–1.340) | <0.0001 | |
| Midwest | 1.147 (1.061–1.240) | 0.0006 | |
| South | 1.093 (1.030–1.160) | 0.0033 | |
| West | 1.154 (1.057–1.261) | 0.0014 | |
| Payer status | |||
| Medicare (ref) | 1.00 | ||
| Medicaid | National | 1.21 (1.110–1.319) | <0.0001 |
| Northeast | 0.982 (0.797–1.211) | 0.8677 | |
| Midwest | 1.179 (0.986–1.410) | 0.0718 | |
| South | 1.138 (0.996–1.281) | 0.0580 | |
| West | 1.516 (1.284–1.790) | <0.0001 | |
| Private insurance | National | 0.77 (0.729–0.812) | <0.0001 |
| Northeast | 0.599 (0.498–0.720) | <0.0001 | |
| Midwest | 0.852 (0.794–0.914) | <0.0001 | |
| South | 0.792 (0.739–0.849) | <0.0001 | |
| West | 0.849 (0.767–0.940) | 0.0016 | |
| Self-pay | National | 0.772 (0.659–0.903) | 0.0013 |
| Northeast | 0.753 (0.612–0.925) | 0.0071 | |
| Midwest | 1.082 (0.937–1.249) | 0.2852 | |
| South | 0.628 (0.471–0.839) | 0.0017 | |
| West | 0.923 (0.731–1.166) | 0.5002 | |
| Low income | National | 1.182 (1.117–1.252) | <0.0001 |
| Northeast | 1.14 (0.981–1.325) | 0.0883 | |
| Midwest | 1.201 (1.098–1.313) | <0.0001 | |
| South | 1.142 (1.056–1.234) | 0.0008 | |
| West | 1.379 (1.140–1.666) | 0.0009 | |
| Large metropolitan hospital | National | 1.75 (1.589–1.928) | <0.0001 |
| Northeast | 1.99 (1.570–2.522) | <0.0001 | |
| Midwest | 1.554 (1.299–1.859) | <0.0001 | |
| South | 1.785 (1.521–2.094) | <0.0001 | |
| West | 1.689 (1.352–2.111) | <0.0001 | |
| Teaching hospital | National | 1.161 (1.011–1.333) | 0.0342 |
| Northeast | 1.236 (0.979–1.561) | 0.0752 | |
| Midwest | 1.222 (1.018–1.466) | 0.0313 | |
| South | 0.79 (0.470–1.328) | 0.3730 | |
| West | 1.047 (0.569–1.927) | 0.8835 | |
| Safety net hospital | National | 1.219 (1.105–1.344) | <0.0001 |
| Northeast | 0.882 (0.685–1.137) | 0.3323 | |
| Midwest | 1.107 (0.954–1.284) | 0.1808 | |
| South | 1.234 (1.047–1.455) | 0.0123 | |
| West | 1.667 (1.410–2.191) | <0.0001 | |
| Hospital ownership: government or private, collapsed (ref) | 1.00 | ||
| Government, nonfederal, public | National | 0.964 (0.807–1.150) | 0.6821 |
| Northeast | 0.107 (0.086–0.134) | <0.0001 | |
| Midwest | 0.876 (0.684–1.121) | 0.2929 | |
| South | 0.618 (0.371–1.030) | 0.0646 | |
| West | 1.15 (0.651–2.033) | 0.6297 | |
| Private, nonprofit | National | 1.089 (0.898–1.322) | 0.3849 |
| Northeast | 0.105 (0.087–0.127) | <0.0001 | |
| Midwest | 0.129 (0.112–0.149) | <0.0001 | |
| South | 0.675 (0.408–1.116) | 0.1254 | |
| West | 1.532 (0.866–2.711) | 0.1430 | |
| Private, investor-owned | National | 1.514 (1.250–1.833) | <0.0001 |
| Northeast | 0.124 (0.100–0.153) | <0.0001 | |
| Midwest | 0.15 (0.128–0.176) | <0.0001 | |
| South | 0.999 (0.601–1.659) | 0.9955 | |
| West | 1.836 (1.055–3.195) | 0.0315 | |
| Weekend ED visit | National | 0.995 (0.971–1.019) | 0.6914 |
| Northeast | 0.971 (0.922–1.022) | 0.2602 | |
| Midwest | 1.008 (1.351–1.839) | 0.7076 | |
| South | 1.016 (1.541–2.108) | 0.3789 | |
| West | 0.97 (0.901–1.406) | 0.4306 |
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