Table 3. Regression analyses testing the mediation of GDS in the relationship between MBI and four domains of WHOQOL-BREF.

	Predictor	Outcome	Estimate(S.E)	p value	R2	Sobel test statistic, p value
Phy Dom						4.43, <0.001
Step 1	MBI	Phy Dom	0.06(0.02)	<0.001	0.10
Step 2	MBI	GDS	-0.14(0.02)	<0.001	0.16
Step 3	GDS	Phy Dom	-0.23(0.04)	<0.001	0.16
Step 4	GDS	Phy Dom	-0.21(0.04)	<0.001	0.15
	MBI		0.03(0.02)	0.120
Psy Dom						4.95, <0.001
Step 1	MBI	Psy Dom	0.06(0.02)	<0.001	0.07
Step 2	MBI	GDS	-0.14(0.02)	<0.001	0.16
Step 3	GDS	Psy Dom	-0.28(0.04)	<0.001	0.16
Step 4	GDS	Psy Dom	-0.26(0.04)	<0.001	0.16
	MBI		0.02(0.02)	0.125
Soc Dom						not applicable
Step 1	MBI	Soc Dom	0.02(0.02)	0.138	0.05
Step 2	MBI	GDS	-0.14(0.02)	<0.001	0.16
Step 3	GDS	Soc Dom	-0.18(0.04)	<0.001	0.10
Step 4	GDS	Soc Dom	-0.18(0.04)	<0.001	0.10
	MBI		-0.00(0.02)	0.841
Env Dom						4.95, <0.001
Step 1	MBI	Env Dom	0.03(0.01)	0.017	0.05
Step 2	MBI	GDS	-0.14(0.02)	<0.001	0.16
Step 3	GDS	Env Dom	-0.21(0.03)	<0.001	0.13
Step 4	GDS	Env Dom	-0.21(0.04)	<0.001	0.13
	MBI		0.01(0.01)	0.725

Each regression is adjusted for age, gender, education, marriage, household cohabitant, MMSE, multi-morbidity (including diabetes, hypertension, heart disease, stroke and cancer).

WHOQOL = World Health Organization Quality of Life Scale-Brief Version; MMSE = Mini-Mental State Examination; MBI = Modified Barthel Index; GDS = Geriatric Depression Scale; Phy Dom = Physical domain; Psy Dom = Psychological domain; Soc Dom = Social relationship domain; Env Dom = Environmental domain