Table 2. Negative binomial generalized estimation equation for the effect of continuity of care on overall emergency room use.

	Incidence rate	Crude IRR	95% CI	Adjusted IRR	95% CI
Continuity of Care Index (COCI)
Low (reference)	0.53
Medium	0.44	0.86**	(0.80, 0.93)	0.89**	(0.82, 0.96)
High (COCI = 1)	0.30	0.61**	(0.57, 0.66)	0.67**	(0.62, 0.71)
Sex
Male (reference)	0.37
Female	0.38	1.01	(0.94, 1.10)	1.04	(0.96, 1.12)
Age, years
20–39 (reference)	0.41
40–65	0.34	0.83*	(0.71, 0.96)	0.74**	(0.64, 0.86)
>65	0.45	1.12	(0.96, 1.31)	0.86	(0.73, 1.00)
Area
Taipei	0.38
North	0.40	1.04	(0.92, 1.18)	0.98	(0.86, 1.11)
Central	0.39	1.00	(0.90, 1.12)	0.94	(0.84, 1.06)
South	0.34	0.91	(0.81, 1.03)	0.82**	(0.72, 0.93)
Kuoshong-Pingdong	0.34	0.88*	(0.78, 0.99)	0.84**	(0.75, 0.94)
East	0.45	1.12	(0.89, 1.41)	1.10	(0.87, 1.40)
Charlson Comorbidity Index
1 (reference)	0.25
2	0.39	1.50**	(1.40, 1.62)	1.36**	(1.26, 1.47)
≥3	0.67	2.51**	(2.33, 2.70)	1.97**	(1.81, 2.15)
Diabetes Complication Severity Index
0 (reference)	0.29
1	0.40	1.32**	(1.22, 1.42)	1.05	(0.97, 1.14)
≥2	0.74	2.42**	(2.24, 2.62)	1.67**	(1.52, 1.82)
Income, New Taiwan $
<20 000 (reference)	0.43
20 000–39 999	0.34	0.84**	(0.78, 0.92)	0.93	(0.85, 1.01)
≥40 000	0.32	0.82**	(0.74, 0.90)	0.87*	(0.79, 0.97)
Fishermen/farmers	0.39	0.96	(0.87, 1.06)	1.01	(0.91, 1.12)

CI, confidence interval; IRR, incidence rate ratio.

*P < 0.05.

**P < 0.01.

1 United States $ ≈ 30 New Taiwan $.