Table 1. Characteristics of study in the baseline.

Metformin	Total		With		Without		P
Variables	n	%	n	%	n	%
Total	2,904		968	33.33	1,936	66.67
Gender
Male	1,245	42.87	415	42.87	830	42.87	Reference
Female	1,659	57.13	553	57.13	1,106	57.13	0.852
Age (years)	70.55±10.66		70.17±10.85		70.74±10.56		0.070
CCI removed DM	0.71±1.16		0.80±1.26		0.67±1.10		0.008
Location
Northern Taiwan	1,013	34.88	439	45.35	574	29.65	Reference
Middle Taiwan	867	29.86	204	21.07	663	34.25	<0.001
Southern Taiwan	775	26.69	244	25.21	531	27.43	<0.001
Eastern Taiwan	224	7.71	74	7.64	150	7.75	0.378
Outlets islands	25	0.86	7	0.72	18	0.93	0.589
Urbanization level
1 (The highest)	817	28.13	362	37.40	455	23.50	<0.001
2	1,187	40.87	393	40.60	794	41.01	0.011
3 (The lowest)	900	40.00	213	22.00	687	35.49	Reference
Level of care
Hospital center	925	31.85	368	38.02	557	28.77	0.274
Regional hospital	1,164	40.08	367	37.91	797	41.17	0.035
Local hospital	815	28.06	233	24.07	582	30.06	Reference
Insured premium (NT$)
<10,000	1,469	50.58	488	50.41	981	50.67	Reference
10,000–14,999	730	25.14	251	25.93	479	24.74	0.375
≧15,000	705	24.28	229	23.66	476	24.59	0.362

CCI = Charlson Comorbidity Index

P: Conditional logistic regression