Table 1. Baseline characteristics of never users and ever users of metformin in the original cohort and in the propensity score matched cohort.

Variables	Original cohort						Matched cohort
	Never users		Ever users		P*	SD	Never users		Ever users		P*	SD
	n	%	n	%			n	%	n	%
	6940		132971				6940		6940
Age (years)	60.96±9.95		58.10±10.04		<0.0001	-29.66	60.96±9.95		61.17±9.22		0.0524	4.18
Obesity	222	3.20	7913	5.95	<0.0001	13.23	222	3.20	198	2.85	0.2344	-2.04
Hypertension	5337	76.90	96678	72.71	<0.0001	-10.23	5337	76.91	5377	77.49	0.4183	1.46
Chronic obstructive pulmonary disease	3065	44.16	55444	41.70	<0.0001	-5.53	3065	44.17	3030	43.67	0.5494	-0.90
Nephropathy	1781	25.66	22312	16.78	<0.0001	-23.61	1780	25.65	1769	25.49	0.8305	-1.40
Eye disease	571	8.23	20648	15.53	<0.0001	22.80	571	8.23	489	7.05	0.0088	-4.62
Dyslipidemia	4437	63.93	93249	70.13	<0.0001	13.62	4437	63.94	4364	62.89	0.1983	-1.68
Stroke	1787	25.75	27045	20.34	<0.0001	-13.61	1787	25.75	1777	25.61	0.8459	-0.23
Ischemic heart disease	2886	41.59	49537	37.25	<0.0001	-9.48	2886	41.59	2903	41.84	0.7698	0.41
Peripheral arterial disease	1195	17.22	23160	17.42	0.6710	0.28	1195	17.22	1181	17.02	0.7524	-0.46
Sulfonylurea	5052	72.80	84780	63.76	<0.0001	-16.61	5052	72.81	5316	76.61	<0.0001	11.43
Meglitinide	552	7.95	4627	3.48	<0.0001	-20.47	551	7.94	514	7.41	0.2380	-1.55
Acarbose	828	11.93	6724	5.06	<0.0001	-24.30	827	11.92	768	11.07	0.1163	-3.30
Insulin	481	6.93	2550	1.92	<0.0001	-25.75	480	6.92	318	4.58	<0.0001	-11.80
Pioglitazone	171	2.46	2939	2.21	0.1622	-0.99	171	2.46	146	2.10	0.1555	-2.74
Rosiglitazone	220	3.17	5860	4.41	<0.0001	6.73	220	3.17	201	2.90	0.3470	-1.73
Cervical cancer screening	3263	47.02	67876	51.05	<0.0001	8.29	3263	47.02	3229	46.53	0.5630	-0.78

Age is expressed as mean ± standard deviation; SD: standardized difference; *by Student’s t test for age and by Chi-square test for other variables.