Table 4. Indexes of additive biological interactive effect of obesity and central obesity on elevated urinary albumin-to-creatinine ratio.

Measure	Un-adjusted			Adjusted
	Estimate	Lower	Upper	Estimate	Lower	Upper
RERI	0.960	0.073	1.847	0.798	0.119	1.476
AP	0.352	0.069	0.635	0.439	0.110	0.768
S	2.252	0.861	5.894	42.743	-	-

RERI, the relative excess risk because of the interaction; AP, the attributable proportion because of the interaction; S, the synergy index. If there was no biological interaction, the confidence interval of RERI and AP include 0, and the confidence interval of S contains 1.