Table 2 Multiple logistic regression analysis of factors associated with frequent ED use

Sex

 Female

ref

 Male

1.06

1.05

1.08

 < .0001

Age (years)

  ≤ 9

ref

 10–19

0.55

0.54

0.57

 < .0001

 20–29

0.60

0.59

0.61

 < .0001

 30–39

0.64

0.62

0.65

 < .0001

 40–49

0.67

0.65

0.68

 < .0001

 50–59

0.68

0.67

0.69

 < .0001

 60–69

0.74

0.72

0.75

 < .0001

  ≥ 70

0.94

0.93

0.96

 < .0001

Region

 Seoul

ref

 Busan

0.96

0.91

1.01

0.1450

 Daegu

0.77

0.74

0.80

 < .0001

 Incheon

1.25

1.22

1.29

 < .0001

 Gwangju

1.36

1.28

1.44

 < .0001

 Daejeon

1.33

1.27

1.38

 < .0001

 Ulsan

0.74

0.70

0.79

 < .0001

 Sejong

0.99

0.88

1.11

0.8798

 Gyeonggi

1.06

1.04

1.08

 < .0001

 Gangwon

1.04

0.98

1.11

0.1867

 Chungcheong

1.16

1.12

1.20

 < .0001

 Jeolla

1.57

1.48

1.65

 < .0001

 Gyeongsang

1.44

1.36

1.51

 < .0001

 Jeju

1.67

1.57

1.78

 < .0001

Insurance types

 National Health Insurance

ref

 Auto insurance

0.70

0.68

0.73

 < .0001

 Industrial accident insurance

0.90

0.79

1.03

0.1312

 Medical Aid (Types 1 and 2)

2.12

2.08

2.16

 < .0001

 General insurance

0.60

0.57

0.64

 < .0001

 Other insurance

0.84

0.77

0.92

0.0002

Residence in Underserved Emergency Medical Services areas

 No

ref

 Yes

0.79

0.77

0.81

 < .0001

Number of emergency medical institutions

 Above the national average

ref

 Below the national average

1.20

1.15

1.25

 < .0001

Number of beds

 Above the national average

ref

 Below the national average

1.04

1.01

1.06

0.0015

Regional income decile

 1^st quartile (lowest)

ref

 2^nd quartile

1.25

1.22

1.28

 < .0001

 3^rd quartile

1.07

1.05

1.10

 < .0001

 4^th quartile

1.12

1.09

1.15

 < .0001

 5^th quartile

1.37

1.33

1.40

 < .0001

 6^th quartile

1.22

1.19

1.25

 < .0001

 7^th quartile

1.01

0.98

1.04

0.4939

 8^th quartile

1.05

1.02

1.08

0.0006

 9^th quartile

0.95

0.93

0.98

0.0002

 10^th quartile (highest)

0.95

0.92

0.98

0.0002

Cancer

 No

ref

 Yes

3.33

3.26

3.39

 < .0001

Hypertension

 No

ref

 Yes

0.87

0.82

0.93

 < .0001

Diabetes

 No

ref

 Yes

1.17

1.11

1.24

 < .0001

Renal failure

 No

ref

 Yes

1.91

1.84

1.98

 < .0001

Mental illness

 No

ref

 Yes

1.60

1.54

1.66

 < .0001

Korean Triage and Acuity Scale

 Level 1 (Resuscitation)

ref

 Level 2 (Emergent)

1.04

0.99

1.10

0.1161

 Level 3 (Urgent)

1.08

1.03

1.14

0.0029

 Level 4 (Less urgent)

0.92

0.88

0.97

0.0013

 Level 5 (Non-urgent)

1.78

1.69

1.88

 < .0001