Table 3 Incidence risk ratio (IRR) and 95 % confidence interval (CI) of inpatient care utilization with four types of status of public and private health insurance in the Korea Health Panel Survey, 2008–2011

Gender (Ref.: Men)

1

1

1

1

 Women

1.08*

1.01–1.16

1.05

0.97–1.12

1.07*

1.00–1.15

1.07*

1.00–1.15

Age (Ref.: 20–29)

1

1

1

1

 30–39

0.81**

0.70–0.95

0.78**

0.67–0.91

0.76**

0.65–0.89

0.76**

0.65–0.89

 40–49

0.67**

0.57–0.79

0.60**

0.51–0.71

0.58**

0.49–0.68

0.58**

0.49–0.68

 50–59

0.85

0.72–1.01

0.73**

0.61–0.88

0.73**

0.61–0.87

0.73**

0.61–0.87

 60 or older

1.31***

1.11–1.55

1.05

0.87–1.26

1.05

0.87–1.26

1.05

0.87–1.26

Chronic disease (Ref.: No)

1

1

1

1

 Yes

2.31***

2.14–2.49

2.27***

2.11–2.45

2.18***

2.03–2.36

2.19***

2.03–2.36

Marital status (Ref.: Single)

1

1

1

1

 Married couple

1.99***

1.72–2.31

1.98***

1.71–2.89

2.08***

1.80–2.41

2.08***

1.80–2.41

 Divorced or Separated

2.55***

2.05–3.17

2.40***

1.93–2.98

2.25***

1.81–2.80

2.25***

1.81–2.80

 Separation by death

2.00***

1.66–2.41

1.91***

1.58–2.30

1.91***

1.59–2.31

1.91***

1.58–2.30

Education (Ref.: College Degree or higher)

1

1

1

 High School to associate

1.23***

1.12–1.35

1.20***

1.10–1.32

1.20***

1.10–1.32

 Middle School to associate

1.26***

1.11–1.43

1.19**

1.05–1.35

1.19**

1.05–1.35

 Elementary School or less

1.36***

1.21–1.54

1.31***

1.16–1.48

1.31***

1.16–1.48

Household income (Ref.: 1^st quartile, lowest)

1

1

1

 2^st quartile

1.06

0.98–1.15

1.06

0.98–1.15

1.06

0.98–1.15

 3^st quartile

1.09*

1.01–1.18

1.07

0.99–1.17

1.07

0.99–1.17

 4^st quartile (highest)

1.15**

1.06–1.26

1.07

0.98–1.16

1.07

0.98–1.17

Healthcare covered by NHI (Ref.: Yes)

1

 No (medical aid)

2.26***

2.01–2.53

Purchase of PHI (Ref.: No)

1

 Yes

1.06

0.98–1.15

NHI status x PHI status (Ref.: Covered by only NHI)

1

 Covered by only the medical aid

2.37***

2.00–2.75

 Covered by both NHI and PHI

1.08

0.99–1.17

 Covered by both the medical aid and PHI

2.38***

1.97–2.76