Table 2. Associations between daily mean O₃ (lag_0-1, ppb) and daily number of mortality adjusted for PM₁₀ in 13 Japanese and Korean cities from 2000 to 2009.

City	Linear Model				Spline Model		Comparison of models
	Beta	SE	P-value	AIC	P-value	AIC	ΔAIC	P-value *
Korea
Seoul	-0.00024	0.000247	0.3412	27824.3	0.0002	27808.0	-16.3	<0.0001
Incheon	-0.00065	0.000418	0.1199	22731.3	0.2592	22731.0	-0.3	0.1121
Daejon	-0.00030	0.000575	0.6046	20058.0	0.6046	20058.0	0.0	0.0016
Daegu	0.00036	0.000421	0.3916	22885.3	0.0588	22881.4	-3.9	0.0125
Gwangju	0.00094	0.000618	0.1300	20248.8	0.1301	20248.8	0.0	0.0039
Busan	0.00095	0.000330	0.0039	24719.2	0.0000	24709.1	-10.1	0.0004
Japan
Ulsan	0.00101	0.000708	0.1537	18690.8	0.1537	18690.8	0.0	0.0026
Sapporo	-0.00014	0.000439	0.7481	23314.4	0.1761	23311.7	-2.7	0.0286
Tokyo	-0.00081	0.000173	0.0000	30326.9	0.0000	30290.8	-36.1	<0.0001
Nagoya	-0.00056	0.000380	0.1400	24704.7	0.0011	24693.7	-11.0	0.0002
Osaka	-0.00124	0.000281	0.0000	26212.4	0.0001	26210.8	-1.6	0.0504
Kitakyushu	-0.00091	0.000403	0.0241	22300.2	0.0155	22296.4	-3.7	0.0128
Fukuoka	-0.00054	0.000475	0.2530	21987.5	0.2460	21987.4	-0.1	0.1373

ΔAIC = AIC of Spline model–AIC of Linear model

*For the difference of the deviances between the linear and spline models.