Background
According to Global Burden of Disease in 2017, there are nearly 3.5 billion population affected by oral diseases around the world [
1]. Oral health is an important public health issue globally, including in China. Among the Chinese population oral diseases is very common, particularly among older adults. According to the 4th national oral health epidemiological survey in China, the prevalence of dental caries and periodontal disease among the age group 55–74 were 96.8% and 92.9%, respectively [
2]. These oral diseases are the main reason for tooth loss among Chinese population [
3]. Factors that increase the risk for caries and periodontal diseases highly relate to health behaviors, such as, smoking, drinking, oral hygiene, dental attendance, eating food high in sugar [
4‐
6]. Edentulism, which refers to the loss of all natural teeth, is a final status for tooth loss and is a good indicator of lifelong exposure to oral health risk factors. According to the 4th survey, the prevalence of edentulism aged 45 and above increased from 12.1% in 2013 to 14.6% in 2015 [
3].
Traditionally, studies exploring possible determinants of oral health have paid most attention to biological and behavioral factors [
7,
8] However, health behavior is also determined by a range of sociopolitical factors, for example, social capital [
9]. Evidence has shown that social capital, which is defined by Putnam as “features of organizations, such as networks, trust and social norms of reciprocity” [
10], is associated with oral health in different contexts [
11‐
13]. For example, in Brazilian, a higher level of neighborhood social capital was reported to have an association with lower risk of dental caries [
14] and lower risk of dental injury [
15] among adolescence. In the US, a study found that more numbers of close friends is associated with fewer decayed teeth among individuals age 60 and above [
16]. In Japan, participation in hobby clubs, sports groups was associated with reduced risk of tooth loss among older people[
17]. The association between social capital and oral health was also found in other countries, including England [
18], Indonesia [
19,
20], South African [
21], Korea [
22], India [
23]. Although studies have explored the association between social capital and different health outcomes in the Chinese context, including, loneliness [
24,
25], depression [
26‐
28], life satisfaction [
29], self-rated health [
30‐
32], mental health [
33,
34], health-related quality of life [
35,
36], cognitive functions [
37], however, no study has explored its association with oral health. Due to different epidemiological characteristics of oral health conditions and differences in political, socioeconomic, cultural context, and health care system in China, social capital may have a different effect on oral health. Therefore, it is important to explore the association in the Chinese context.
In addition, to explore the mechanism between social capital and oral health, it is important to understand the association of different dimensions of social capital with oral health. Islam developed a very useful division for social capital and broke social capital into two dimensions: cognitive social capital and structural social capital [
11]. Cognitive dimension of social capital refers to individuals’ subjective perception of the community or society the individuals belong to, while structural social capital refers to the actual behavior to build social networks [
38]. Giordano and colleagues suggested that researchers should both explore the cognitive and structural dimensions of social capital [
39], due to it may impacts health through different pathways [
40]. Structural social capital is shaped by institutions, policies, and culture, which potentially have strong impact on objective health of individuals, while cognitive social capital is suggested to affect health through psychosocial mechanisms and potentially have impact on subjective health of individuals [
40].
Therefore, the present study aims to explore the association of cognitive and structural social capital at the individual- and community-level and edentulism among adults aged 50 and over in China.
Results
The socioeconomic, demographic, behavioral characteristics, and chronic health condition of the study sample were illustrated in Table
1. A total of 12,856 individuals aged 50 and above were included in the analysis. The overall average age of 12,856 respondents in 127 communities was 63.0 (standard deviation; 9.3) years old. The overall prevalence of participants being edentulate was 9.1% (95% CI 8.3–10.0). The majority of the participants of the sample population were between 50 to 69 years old (77.3%), currently married (85.4%), completed primary school and above (58.7%), never smoker (64.1%), and never drinker (66%), sufficient fruit or vegetable intaking (90.1%), having no chronic diseases (61%). Nearly half (47.6%) of the participants lived in urban areas. The proportion of highest and lowest wealth quintile were, respectively, 21.9% and 16.1%.
Table 1
Sociodemographic characteristics of the study population (n = 12,856)
Sex | Marital status |
male | 6393 (49.8) | Married | 10951 (85.4) |
female | 6445 (50.2) | Unmarried | 1878 (14.6) |
Age | Numbers of chronic diseases |
50-59 | 5803 (45.2) | No chronic diseases | 7844 (61.1) |
60-69 | 4104 (32.0) | 1 chronic disease | 3415 (26.6) |
70-79 | 2376 (18.5) | 2 chronic diseases | 1220 (9.5) |
80- | 554 (4.3) | 3–6 chronic diseases | 347 (2.7) |
Residence | Smoking status |
Urban | 6111 (47.6) | Never smoker | 8195 (64.1) |
Rural | 6727 (52.4) | Not current smoke | 844 (6.6) |
Education | Current smoker, not daily | 320 (2.5) |
No formal education | 2855 (22.2) | Current daily smoker | 3426 (26.8) |
Less than primary | 2455 (19.1) | | |
Primary completed | 2727 (21.2) | | |
Secondary completed | 2577 (20.1) | | |
High school completed | 1640 (12.8) | | |
University and above | 585 (4.6) | | |
House household income quintile | | |
Q1 (lowest) | 2056 (16.1) | | |
Q2 | 2309 (18.0) | | |
Q3 | 2617 (20.5) | | |
Q4 | 3008 (23.5) | | |
Q5 (highest) | 2805 (21.9) | | |
Table
2 shows the distribution of edentulism and the crude odds ratio of covariables for edentulism. Descriptive statistics show that the prevalence of edentulism is higher among females (10.1%) than males (8.0%). The age group 80+ has the highest prevalence of edentulism (37.1%). Those living in rural areas (10.4%) have higher prevalence of edentulism than those living in urban areas (7.6%). Compared with those married (7.6%), those unmarried (17.6%) have higher prevalence of edentulism. Those have lower educational level and in lower household income quintile have higher prevalence of edentulism than the counterpart. Crude odds ratio of covariables (Table
2) were calculated by univariate multilevel logistic regression analysis. The crude odds ratio of covariates identified variables that were associated with edentulism. Edentulism was significantly associated with being females, oldest age group, no formal education, unmarried, lowest household income, living in rural area, smoking, and having one chronic diseases.
Table 2
Distribution of covariables by edentate status and crude odds ratio of covariables for edentulism (n = 12,856)
Sex |
male | 5878 (92.0) | 514 (8.0) | Reference |
female | 5795 (89.9) | 653 (10.1) | 1.32 (1.16–1.50)*** |
Age |
50-59 | 5639 (97.2) | 164 (2.8) | Reference |
60-69 | 3757 (91.5) | 347 (8.5) | 3.36 (2.70–4.18)*** |
70-79 | 1925 (81.0) | 545 (19.0) | 9.94 (7.64–12.91)*** |
80- | 349 (62.9) | 206 (37.1) | 24.20 (17.11–34.22)*** |
Residence |
Urban | 5647 (92.4) | 464 (7.6) | Reference |
Rural | 6027 (89.6) | 700 (10.4) | 1.49 (1.12–1.98)** |
Education |
No formal education | 2350 (82.3) | 505 (17.7) | 6.83 (4.12–11.32)*** |
Less than primary | 2200 (89.6) | 255 (10.4) | 3.51 (2.12–5.81)*** |
Primary completed | 2522 (92.5) | 205 (7.5) | 2.30 (1.36–3.88)** |
Secondary completed | 2448 (95.0) | 129 (5.0) | 1.49 (0.91–2.45) |
High school completed | 1587 (96.8) | 52 (3.2) | 0.95 (0.56–1.59) |
University and above | 565 (96.7) | 19 (3.3) | Reference |
Household income quintile |
Q1 (lowest) | 1740 (84.6) | 316 (15.4) | 3.69 (2.69–5.05)*** |
Q2 | 2057 (89.1) | 252 (10.9) | 2.16 (1.52–3.07)*** |
Q3 | 2349 (89.8) | 267 (10.2) | 1.91 (1.41–2.59) *** |
Q4 | 2812 (93.5) | 196 (6.5) | 1.31 (0.94–1.82) |
Q5 (highest) | 2669 (95.1) | 137 (4.9) | Reference |
Marital status |
married | 10114 (92.4) | 837 (7.6) | Reference |
unmarried | 1548 (82.4) | 322 (17.6) | 2.61 (2.21–3.07)*** |
Smoking status |
Never smoker | 7434 (90.8) | 755 (9.2) | Reference |
former smoker | 729 (86.4) | 115 (13.6) | 1.59 (1.23–2.06)*** |
Current smoker, not daily | 303 (94.4) | 18 (5.6) | 0.59 (0.36–0.96)* |
Current daily smoker | 3158 (92.1) | 272 (7.9) | 0.79 (0.66–0.95)* |
Numbers of chronic diseases |
No chronic diseases | 7246 (92.4) | 598 (7.6) | Reference |
1 chronic disease | 3076 (89.9) | 344 (10.1) | 1.39 (1.16–1.67)*** |
2 chronic diseases | 1056 (86.2) | 170 (13.8) | 2.16 (1.73–2.71)*** |
3-6 chronic diseases | 291 (83.8) | 56 (16.2) | 2.68 (1.86–3.85)*** |
Table
3 shows crude odds ratio of social capital variables for edentulism calculated by uni-variate multilevel logistic regression. At individual level lowest cognitive and structural social capital was,respectively, associated with 1.34 (95% CI 1.08–1.67) and 2.44 (95% CI 1.92–3.11) times higher odds of edentulism compared with highest social capital group. At community level, lowest cognitive and structural social capital was, respectively, associated with 1.18 (95% CI 0.83–1.66) and 1.81 (95% CI 1.28–2.58) times higher odds of edentulism compared with highest social capital group. Table
4 shows adjusted and unadjusted odds ratio of social capital variables for edentulism. Model 0 was a null model including no explanatory variable, which is baseline for community differences. In model 1, community-level social capital was included, individuals living in low structural social capital areas have higher odds for edentulism. In model 2, individual and community level social capital was included. Individual-level low structural social capital was significantly associated with edentulism with odds of 2.39 (95% CI 1.86–3.08). No significant association was found between community social capital variables, individual cognitive social capital and edentulism. After adjusting for potential confounders (model 3), including socioeconomic factor, demographic factors and chronic condition, only structural dimension of individual and community social capital were significantly associated with edentulism, the odds were respectively, 1.54 (95% CI 1.18–2.02) and 2.11 (95% CI 1.45–3.07). In the final model (model 4), further include a potential mediator (smoking), the structural dimension of both level social capital is still significantly associated with edentulism. The intraclass correlation for model 0 was 13.53%, which indicated that 13.53% of individual health variance was attributable to the community differences. After adjusting for all explanatory variables in final model, intraclass correlation reduced to 10.93%, indicating the model fits better.
Table 3
Crude odds ratios (OR) of social capital variables for edentulism
Individual cognitive social capital |
Low | 1.34 (1.08–1.67)** |
Mediate | 1.02 (0.82–1.27) |
High | Reference |
Individual structural social capital |
Low | 2.44 (1.92–3.11)*** |
Mediate | 1.52 (1.25–1.84)*** |
High | Reference |
Community cognitive social capital |
Low | 1.18 (0.83–1.66) |
Mediate | 1.21 (0.84–1.75) |
High | Reference |
Community structural social capital |
Low | 1.81 (1.28–2.58)** |
Mediate | 1.07 (0.79–1.46) |
High | Reference |
Table 4
Multilevel logistic regression model for edentulism unadjusted and adjusted by covariates
Individual cognitive SCf |
Low | | | 1.17 (0.96–1.44) | 1.13 (0.91–1.41) | 1.14 (0.91–1.43) |
Mediate | | | 0.93 (0.76–1.14) | 0.91 (0.74–1.11) | 0.92 (0.75–1.12) |
High | | | Reference | Reference | Reference |
Individual structural SCf |
Low | | | 2.39 (1.86–3.08)\(^{***}\) | 1.54( 1.18–2.02)\(^{**}\) | 1.54 (1.18–2.01)\(^{**}\) |
Mediate | | | 1.48 (1.20–1.82)\(^{***}\) | 1.25 (1.00–1.57)\(^{*}\) | 1.24 (0.99–1.55) |
High | | | Reference | Reference | Reference |
Community cognitive SCf |
Low | | 1.08 (0.76–1.53) | 1.00 (0.70–1.44) | 1.05 (0.74–1.50) | 1.03 (0.72–1.48) |
Mediate | | 1.12 (0.78–1.61) | 1.08 (0.76–1.55) | 1.02 (0.71–1.47) | 1.01 (0.70–1.45) |
High | | Reference | Reference | Reference | Reference |
Community structural SCf |
Low | | 1.77 (1.24–2.53)** | 1.37 (0.94–1.99) | 2.11 (1.45–3.07)*** | 2.14 (1.47–3.12)*** |
Mediate | | 1.04 (0.76–1.43) | 0.91 (0.66–1.27) | 1.10 (0.79–1.54) | 1.11 (0.79–1.55) |
High | | Reference | Reference | Reference | Reference |
Random effects |
Community variance (SE) | 0.515 (0.097) | 0.449 (0.091) | 0.469 (0.095) | 0.397 (0.083) | 0.403 (0.085) |
Intraclass correlation (%) | 13.53% | 12.02% | 12.49% | 10.78% | 10.93% |
Discussion
The present study investigated the association of cognitive and structural social capital at both individual- and community-level and edentulism among adults aged 50 and over in China. After adjusting for potential confounders and a potential mediator, individual with low structural social capital and living in areas with low structural social capital was independently associated with higher odds for edentulism. While cognitive dimension social capital was not associated with edentulism in this study. The result indicates that the structural dimension of social capital has a larger influence on edentulism than the cognitive dimension among Chinese adults aged 50 years and over.
At the individual level, the result of the association between structural social capital and edentulism is consistent with the previous study by Rouxel et al, who conducted a cross-sectional study of 8552 individuals aged 50 years and older in the English population and found that structural social capital—as measured by volunteer status and membership in organizations—was associated with edentulism [
40]. Also, a cross-sectional study conducted in Korea found that having less than one general social network (structural social capital) was associated with higher risk of poor chewing ability among the old population aged 70 and over in the rural area. Also, other studies that didn’t differentiate the cognitive and structural social capital found a consistent association between individual structural social capital and the oral health measured by number of remaining teeth [
17,
43,
48,
49]. Despite these studies used different measurements for structural social capital, their findings are consistent. This study didn’t find an association between individual cognitive social capital and edentulism. However, cognitive social capital is often associated with subjective oral health indicators reported by other studies, such as self-reported oral health [
18,
40,
50]. This inconsistency in the association between individual cognitive social capital and oral health might be that cognitive social capital impact oral health through psychosocial pathway and was suggested affect individual’s subjective health (e.g. self-reported oral health), rather than objective oral health measurement (e.g. edentulism).At community level, the present study found that it is the structural dimension of social capital, not the cognitive dimension, is associated with higher odds of edentulism. This finding is also consistent with a previous study. Koyama and colleagues conducted a longitudinal cohort study on community social capital and tooth loss and found that civic participation at baseline is associated with dental loss among Japanese older adults, but not community trust and attachment [
17].
The mechanism between social capital and health is not fully understood. There are several hypothesized ways linking social capital and oral health that may explain our findings. Firstly, social capital may impact oral health through a psychosocial pathway, and it has been reported that individual with lower social capital is vulnerable to psychosocial stressors, thus, deteriorate immune system and ability of the body to defence oral bacteria [
51]. Also, psychosocial stressors may trigger coping mechanisms related to health-compromising behaviors which increase the risk of dental caries and periodontal diseases, such as, smoking, eating sweet food, drinking alcohol [
52]. In addition, social capital can impact oral health through increasing access to dental health care. For example, friends or family members could help to drive them to a hospital or make a dental appointment for them. Moreover, at community level, individuals can benefit from being members of a community. A closely connected community has high level of collective efficiency, which can promote collective action. For example, lobby local authorities for increasing access to health care. Another group-level mechanism is informal social control, which is the ability of a community to maintain social order. In a cohesive community, members are more likely to intervene when witnessing misbehavior, such as health-compromising behavior. Moreover, community social capital can impact health through social contagion. For instance, oral health-related information or behavior norms spread more quickly in a tight-knit community.
In the theoretical framework, oral health related behaviour, smoking, was included as a potential mediator. Previous studies found that social capital is associated with smoking [
53]. In our study, smoking is significantly associated with edentulism in the final model. Also, smoking was found a strong association with oral health reported by other study [
54]. Thus, these associations suggested the potential mediator effect of smoking on association between social capital and oral health. Besides, other oral health related behaviors, like eating sweet and access to dental health care also are potential mediators of interest. Future studies are needed to further explore their mediator effect to better understand the mechanism between social capital and oral health.
This study have explored the association of cognitive and structural dimensions of social capital and oral health in Chinese context. It is important to understand the influence of social capital in the Chinese context. Firstly, as a result of dental health care is expensive in China, and most of the cost is not covered by medical insurance, which increase the importance of the role of social capital. In addition, due to high state ownership in China, government officials in China have control on more resources than those in other countries, which means that having relationship with government officials may receive more potential benefit [
55]. Lastly and most importantly, China had long time implemented “one child policy”, which increased the number of older population living alone and reduced the number of close ties (having one child) of older population [
56]. Those unique context make China an important research object. Despite this study have explored association between cognitive and structural dimension social capital and edentulism. It is also important to understand the influence of other forms of social capital in the Chinese context. For example, some studies found that different dimensions of social capital play a different role in oral health. For example, in Japan, a cross-sectional study found that horizontal social capital, which refers to relationship ties that exist among equal individual or groups who have equal or similar access to power or resources, play a more important role in oral health among the old population than vertical social capital [
43]. Moreover, a cross-sectional study of 967 students aged 18 and 19 years showed that it was vertical trust (trust between students and teachers), but not horizontal trust (trust between students), was associated with poor self-reported oral health [
57]. Additionally, among the Brazilian population, a multilevel cross-sectional study found that bonding social capital was associated with dental pain, but not bridging social capital [
44]. Understanding which form of social capital has a more important effect on oral health can help to develop a more effective intervention for oral health.
One strength of the present study is that we both assessed individual- and community-level social capital using multilevel perspective. Social capital is both characteristics of individual and community [
38]. An individual can mobilize community resources through their individual network. Another strength of the study is that it used a relatively large sample size and the data were nationally representative of community-dwelling aged 50 and above in China. In addition, the data was face-to-face collected using a valid questionnaire. The questionnaire had been tested by a polit study in three developing countries (Ghana, India and the Republic of Tanzania) and performed well with good face validity [
58]. However, there were some limitations of the study. First, it was a cross-sectional study. We don’t know temporal sequencing of social capital and edentulism. Thus, we can not make a causal inference. In addition, we can not rule out reverse causality between social capital and edentulism. For example, edentulism may lead to health selection. Individuals with bad oral health may reduce social participation due to embarrassment caused by teeth. A future prospective study is needed to further explore the relationship between social capital and oral health. Second, information on use of prosthesis was lacking in SAGE data, which might be a potential factor that affect social participation. Future study is needed to take into account the use of prosthesis of edentulism individuals. In addition, information on edentulism was collected by self-report which may introduce information bias and social desirability bias. However, edentulism is not a sensitive issue in aged 50 and older adults in Chinese population and collected face-to-face by well-trained interviewers. The bias was considered to be minimal in our study. Third, the questions used for measurement of social capital may not have captured the whole dimension of social capital, because of the concept of social capital is still controversary, which inevitably result in divergent measurements and controversial operationalisations. Despite there is no best measurement for social capital, we used measurement commonly used by previous studies (social participation, trust, safety) [
59]. The internal consistency of the scales we used for measuring social capital was not perfect, but was adequate with a value of Cronbach alpha above 0.6 [
60]. Fourth, the measurement of individual-level trust in the present study, which is commonly used by previous studies for measurement of social capital [
59], cannot distinguish between the actual trustworthiness of others and an individual’s tendency to trust others. We were interested in whether interpersonal trust or a trustworthy environment have a protective effect on oral health, not an individual’s tendency to trust. Thus, an individual’s variance of the tendency to trust may have biased the result of the study. Finally, the construction of community variables from individual level is one limitation. Community level social capital were measured by aggregating data, which may risk multilinearity due to variables were from same data source. Mean centering was used in our study to reduce multilinearity caused by aggregating data.
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