Table 1.

Baseline Characteristics of Veterans with Diabetes and Metformin Use and the Comparison Group (No Diabetes and No Metformin Use) at a single Veterans Affairs Medical Center, 2002-2012

Characteristics	Diabetes and Metformin (N=3687)		No Diabetes No Metformina (N=13,258)		P b
Age (years), Mean (SD)	60.9 (8.2)		61.6 (9.8)		<0.001*
Body Mass Index (kg/m2), Mean (SD)	(n=3670) 30.5 (5.9)		(n=8864) 26.7 (6.2)		0.0008*
Serum vitamin B12 (pg/dL), Mean (SD)	(n=1369) 439.2 (276.4)		(n=4301) 522.4 (296.7)		0.0015*
Serum creatinine (mg/dL), Mean (SD)	(n=3668) 1.1 (1.0)		(n=8600) 1.2 (0.9)		<0.0001*
	n	(%)	n	(%)
Age group (years)
50-59	2101	57.0	7567	57.1	<0.0001*
60-69	965	26.2	2760	20.8
70-79	544	14.8	2132	16.1
≥80	77	2.1	799	6.0
Sex
Male	3629	98.4	12,778	96.4	<0.0001*
Female	58	1.6	480	3.6
Race and ethnicity
Non-Hispanic, White	2517	68.3	7154	54.0	<0.0001*
Non-Hispanic, Black	928	25.2	4938	37.3
Other	242	6.6	1166	8.8
Body Mass Index (kg/m2)
Low (<18.5)	25	0.7	580	6.5	<0.0001*
Normal (18.5-24.9)	533	14.5	3171	35.8
Overweight (25.0-29.9)	1354	36.9	2849	32.1
Obese (≥30)	1758	47.9	2264	25.5
Number of years treated at the VAMC
1-3	397	10.8	7653	57.7	<0.0001*
4-6	1093	29.6	2530	19.1
7-10	2197	59.6	3075	23.2
Received vitamin B12 assessmentc
Yes	1371	37.2	4325	32.6	<0.0001*
Vitamin B12 concentration (pg/dL)
<170	104	7.6	129	3.0	<0.0001*
170-300	398	29.1	822	19.1
>300	867	63.3	3350	77.9
Serum creatinine concentration (mg/dL)
<1.3	3126	85.2	6605	76.8	<0.0001*
≥1.3	542	14.8	1995	23.2

^ano other antihyperglycemics

^bChi square test for categorical variables and two-sample t test for continuous variables.

^cAssessment any time after 6 months of consecutive metformin therapy among exposed, and anytime during the study period among unexposed.

^*Statistical significance set at P < 0.05; Frequencies may not equal total due to missing data.

SD, Standard Deviation; VAMC, Veterans Affairs Medical Center