Table 2. Demographic and baseline characteristics of the exacerbated COPD cohort.

	Before propensity score match				p value	After propensity score match				p value
	Metformin users (n = 14001)		Metformin non-users (n = 21613)			Metformin users (n = 7721)		Metformin non-users (n = 7721)
	n	%	n	%		n	%	n	%
Gender					0.97					0.32
Female	4686	33.5	7238	33.5		2562	33.2	2620	33.9
Male	9315	66.5	14375	66.5		5159	66.8	5101	66.1
Age					<0.0001					0.93
40–64	4797	34.3	3876	17.9		1976	25.6	1971	25.5
≧65	9204	65.7	17737	82.1		5745	74.4	5750	74.5
mean(SD)	68.9(11.6)		75.1(11.1)		<0.0001	71.8(11.0)		71.8(11.4)		0.96
Diabetes duration (years)
Mean (SD)	6.20(3.64)		6.27(3.75)		0.06	5.67(3.73)		5.75(3.56)		0.15
Charlson comorbidity index					<0.0001					0.87
0	1346	9.61	1248	5.77		585	7.58	579	7.50
1	2499	17.8	3117	14.4		1240	16.1	1219	15.8
≧2	10156	72.5	17248	79.8		5896	76.4	5923	76.7
DCSI score					<0.0001					0.80
0	9049	64.6	15207	70.4		5117	66.3	5133	66.5
1	1456	10.4	1710	7.91		736	9.53	712	9.22
≧2	3496	25.0	4696	21.7		1868	24.2	1876	24.3
Antihypertensive drugs
ACEI/ARB	8985	64.2	8610	39.8	<0.0001	4164	53.9	4166	54.0	0.97
β-blockers	5228	37.3	5134	23.8	<0.0001	2395	31.0	2425	31.4	0.60
Calcium-channel blockers	8907	63.6	9664	44.7	<0.0001	4363	56.5	4395	56.9	0.60
Diuretics	6309	45.1	6486	30.0	<0.0001	2931	38.0	2939	38.1	0.89
Other antihypertensives	2813	20.1	2712	12.5	<0.0001	1295	16.8	1261	16.3	0.46
Antidiabetic drugs
Oral antidiabetic agents					<0.0001					0.74
0–1	8368	59.8	20593	95.3		6770	87.7	6799	88.1
2	3500	25.0	821	3.80		756	9.79	728	9.43
>2	2133	15.2	199	0.92		195	2.53	194	2.51
Insulin	8722	62.3	6706	31.0	<0.0001	3782	49.0	3777	48.9	0.94
COPD drugs
Short-actingβ2bronchodilators	2856	20.4	2642	12.2	<0.0001	1294	16.8	1298	16.8	0.93
Long-actingβ2bronchodilators	200	1.43	187	0.87	<0.0001	82	1.06	92	1.19	0.45
Anticholinergic agent	1960	14.0	2025	9.37	<0.0001	971	12.6	931	12.1	0.33
Inhaled corticosteroids	885	6.32	590	2.73	<0.0001	313	4.05	327	4.24	0.57
systemic corticosteroid	6110	43.6	5884	27.2	<0.0001	2836	36.7	2818	36.5	0.76
Methylxanthine	7818	55.8	8571	39.7	<0.0001	3859	50.0	3858	50.0	0.99
Other drugs
Statin	6271	44.8	3648	16.9	<0.0001	2375	30.8	2351	30.4	0.68
Aspirin	6531	46.6	6263	29.0	<0.0001	2997	38.8	2981	38.6	0.79

Abbreviation: DCSI, diabetes complications severity index score; ACEI, angiotensin converting enzyme–inhibitor; ARB, angiotensin II receptor–blocker.