Table 1. Demographic and baseline characteristics of the stable COPD cohort.

	Before propensity score match				p value	After propensity score match				p value
	Metformin users (n = 40597)		Metformin non-users (n = 39529)			Metformin users (n = 19505)		Metformin non-users (n = 19505)
	n	%	n	%		n	%	n	%
Gender					<0.0001					0.46
Female	18850	46.4	19269	48.7		9252	47.4	9325	47.8
Male	21747	53.6	20260	51.3		10253	52.6	10180	52.2
Age					<0.0001					0.0004
40–64	22003	54.2	16577	41.9		9066	46.5	9417	48.3
≧65	18594	45.8	22952	58.1		10439	53.5	10088	51.7
mean(SD)	63.2(10.8)		67.4(11.6)		<0.0001	65.4(10.7)		65.4(11.4)		0.57
Diabetes duration (years)
Mean (SD)	7.01(3.61)		6.86(3.79)		<0.0001	6.40(3.74)		6.54(3.71)		0.0002
Charlson comorbidity index					<0.0001					0.76
0	24335	59.9	20365	51.5		11200	57.4	11157	57.2
1	6184	15.2	5636	14.3		2797	14.3	2775	14.2
≧2	10078	24.8	13528	34.2		5508	28.2	5573	28.6
DCSI score					<0.0001					0.87
0	30989	76.3	31486	79.7		15154	77.7	15135	77.6
1	4433	10.9	3425	8.66		1922	9.9	1953	10.0
≧2	5175	12.7	4618	11.7		2429	12.5	2417	12.4
Antihypertensive drugs
ACEI/ARB	27026	66.6	16965	42.9	<0.0001	10892	55.8	10829	55.5	0.52
β-blockers	18791	46.3	13665	34.6	<0.0001	7898	40.5	8030	41.2	0.17
Calcium-channel blockers	24842	61.2	18116	45.8	<0.0001	10684	54.8	10719	55.0	0.72
Diuretics	13425	33.1	8414	21.3	<0.0001	5082	26.1	5153	26.4	0.41
Other antihypertensives	6689	16.5	4541	11.5	<0.0001	2591	13.3	2611	13.4	0.77
Antidiabetic drugs
Oral antidiabetic agents					<0.0001					0.12
0–1	23845	58.7	38038	96.2		17943	92.0	18039	92.5
2	9788	24.1	1178	2.98		1251	6.41	1153	5.91
>2	6964	17.2	313	0.79		311	1.59	313	1.60
Insulin	14121	34.8	4568	11.6	<0.0001	3564	18.3	3415	17.5	0.049
COPD drugs
Short-actingβ2bronchodilators	1825	4.50	1168	2.95	<0.0001	709	3.63	712	3.65	0.94
Long-actingβ2bronchodilators	112	0.28	102	0.26	0.62	49	0.25	57	0.29	0.44
Anticholinergic agent	825	2.03	696	1.76	0.005	369	1.89	370	1.90	0.97
Inhaled corticosteroids	978	2.41	578	1.46	<0.0001	390	2.00	394	2.02	0.89
systemic corticosteroid	11442	28.2	7389	18.7	<0.0001	4405	22.6	4420	22.7	0.86
Methylxanthine	14206	35.0	8866	22.4	<0.0001	5376	27.6	5425	27.8	0.58
Other drugs
Statin	23616	58.2	11270	28.5	<0.0001	8723	44.7	8839	45.3	0.24
Aspirin	18656	46.0	11585	29.3	<0.0001	7276	37.3	7329	37.6	0.58

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