3.1 Sample characteristics
Table 1 shows the basic information of socio-demographic characteristics, SES, social support and oral health of MEFC. It was illustrated that 85.6% of the MEFC were from rural areas, while 14.4% from urban areas; most MEFC were female (73.1%), aged 60-65(55.8%), married (87.9%). As for SES, majority of MEFC had an education level of primary school and below (56.4%), job before retire were farming, forestry, livestock and fishing (75.2%), monthly household income were 241~3000RMB (47.1%). With respect to social support, the mean score of social support was 38.88±6.63 among the MEFC in Weifang City, China. As for the oral health, the mean score of GOHAI was 54.95±6.47 for the MEFC in Weifang City, China.
Table 1 Descriptive characteristic of participants by hukou
Variable
|
n (%)/M(S.D.)
|
Rural
|
Urban
|
χ2/t
|
P
|
n (%)/M(S.D.)
|
n (%)/M(S.D.)
|
Observations
|
613(100)
|
525(85.6)
|
88(14.4)
|
|
|
Gender
|
|
|
|
17.950a
|
0.001
|
Male
|
165(26.9)
|
125(23.8)
|
40(45.5)
|
|
Female
|
448(73.1)
|
400(76.2)
|
48(54.5)
|
|
Age
|
|
|
|
11.684 a
|
0.009
|
60-65
|
342(55.8)
|
304(57.9)
|
38(43.2)
|
|
66-70
|
171(27.9)
|
143(27.2)
|
28(31.8)
|
|
71-80
|
80(13.1)
|
65(12.4)
|
15(17.0)
|
|
>80
|
20(3.2)
|
13(2.5)
|
7(8.0)
|
|
Marital status
|
|
|
|
0.860 a
|
0.354
|
Married
|
539(87.9)
|
459(87.4)
|
80(90.9)
|
|
Unmarried/Divorced/Widowed
|
74(12.1)
|
66(12.6)
|
8(9.1)
|
|
Education
|
|
|
|
63.457 a
|
0.001
|
Primary school and below
|
346(56.4)
|
322(61.3)
|
24(27.3)
|
|
Junior high school
|
158(25.8)
|
135(25.7)
|
23(26.1)
|
|
High school and above
|
109(17.8)
|
68(13.0)
|
41(46.6)
|
|
Job before Retire
|
|
|
|
208.864 a
|
0.001
|
Farming, Forestry, Livestock and Fishing
|
461(75.2)
|
449(85.5)
|
12(13.6)
|
|
Others
|
152(24.8)
|
76(14.5)
|
76(86.4)
|
|
Monthly household income
|
|
|
|
176.751 a
|
0.001
|
≤240RMB
|
270(27.7)
|
168(32.0)
|
2(2.3)
|
|
241~3000RMB
|
289(47.1)
|
275(52.4)
|
14(15.9)
|
|
>3000RMB
|
154(25.1)
|
82(15.6)
|
72(81.8)
|
|
Social support
|
38.88(6.63)
|
|
|
|
|
Utilization
|
6.94(2.26)
|
6.86(2.23)
|
7.43(2.37)
|
-2.21b
|
0.027
|
Subjective
|
23.47(4.29)
|
23.45(4.76)
|
23.58(5.00)
|
-0.229 b
|
0.819
|
Objective
|
8.47(1.64)
|
8.44(1.61)
|
8.70(1.78)
|
-1.425 b
|
0.155
|
Oral health
|
54.95(6.47)
|
|
|
|
|
Physiological function
|
17.35(3.44)
|
17.21(3.49)
|
18.18(3.03)
|
-2.730 b
|
0.007
|
Psychosocial function
|
24.10(2.06)
|
24.03(2.15)
|
24.50(1.35)
|
-2.725 b
|
0.007
|
Pain and discomfort
|
13.50(2.12)
|
13.41(2.14)
|
14.03(1.86)
|
-2.841 b
|
0.005
|
Notes: a=Chi-square test;
b=t-test;
S.D.: Standard deviation.
Concerning the rural and urban differences, as shown in Table 1, statistically significant differences were found between hukou and gender (P < 0.001), age (P = 0.009), education (P < 0.001), job before retire (P < 0.001), monthly household income (P < 0.001), and social support utilization dimensions (P = 0.027). It was noted that statistically significant difference were also found between hukou and the three dimensions of GOHAI (physiological function (P = 0.007), psychosocial function (P = 0.007), pain and discomfort (P = 0.005)).
3.2 Model fitness indices
Table 2 shows the model fitness indices of the structural equation model. The estimated value of model fitness for the model were: CMIN/DF =1.675 in the range of 1-3, GFI = 0.985 > 0.90, AGFI = 0.973 > 0.90, NFI=0.967> 0.90, IFI=0.986> 0.90, CFI = 0.986 > 0.90 and RMSEA = 0.033 < 0.05, indicating that the theoretical model fit the empirical data very well.
Table 2 Structural equation model fitness index
indexes
|
CMIN/DF
|
GFI
|
AGFI
|
NFI
|
IFI
|
CFI
|
RMSEA
|
P
|
Cut-off value
|
1-3
|
≥0.90
|
≥0.90
|
≥0.90
|
≥0.90
|
≥0.90
|
≤0.05
|
>0.05
|
Observations
|
1.675
|
0.985
|
0.973
|
0.967
|
0.986
|
0.986
|
0.033
|
0.020
|
Note: CMIN = Chi square; DF= degree of freedom; GFI = Goodness of Fit Index; AGFI = Adjusted Goodness of Fit Index; NFI=Normed Fit Index; IFI=Incremental Fit Index; CFI = Comparative Fitness Index; RMSEA = Root-mean square error of approximation.
3.2 The standardized total, direct, and indirect effects on oral health with social support as mediators
Specifically, bootstrap test suggested that after adjusting for covariates, Figure 1 and Table 3 showed that the total effect of SES on oral health was 0.24 (95% CI: 0.137–0.323, P < 0.005). The direct effect of SES on oral health was 0.22 (95% CI: 0.105–0.317, P < 0.001). The indirect mediating effect via social support was 0.03 (95% CI: 0.003–0.064, P < 0.001). The effects above were all statistically significant since the 95% CI excluded zero, implying he association between SES and oral health was partially mediated by social support; of which the indirect effect accounted for 12.0% of the total effect.
Table 3 The standardized total, direct, and indirect effects
Model pathways
|
Standardized effect value
|
S.D.
|
95% C.I.
|
Mediating effect
|
Total effect SES →oral health
|
0.25*
|
0.053
|
(0.115,0.336)
|
100%
|
Direct effect SES →oral health
|
0.22*
|
0.053
|
(0.105,0.317)
|
88%
|
Indirect effect SES →social support →oral health
|
0.03*
|
0.015
|
(0.003,0.064)
|
12%
|
SES →social support
|
0.15**
|
social support →oral health
|
0.17**
|
Notes: SES= socioeconomic status; S.D.= Standard Deviation; C.I.= Confidence Interval; *P-value<0.001;**P-value<0.05.