Table 6.

Event rates, incidence rates, and number needed to treat for all-cause mortality for comparison of metformin with non-metformin.

	All-cause mortality in whole population (n = 372)	All-cause mortality in the HbA1c ≥7% subgroup (n = 226)
Events/total number
Metformin	11/113	4/67
Non-metformin	56/259	36/159
P-value*	0.269	0.045
Incidence rate, %
Metformin	9.7	6
Non-metformin	21.6	22.6
Difference	11.9	16.6
Relative risk reduction, %	55	73
Number needed to treat
1-year	44	46
2-year	32	20
3-year	20	10
4-year	12	8

^*Events of all-cause mortality were estimated using Cox regression models. Adjusted covariables included age, gender, body mass index, cigarette smoking, systemic blood pressure, diastolic blood pressure, New York Heart Association class, left ventricular ejection fraction, duration of diabetes and heart failure, whether living with hypertension, atrial fibrillation, coronary heart disease, or cerebral infarction, glycated hemoglobin, estimated glomerular filtration rate, hemoglobin, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, triglyceride, left atrial, sulfonylureas, glinides, glucosidase inhibitors, insulin.