Community Dent Oral Epidemiol 2015; 43; 97–105 All rights reserved
Ó 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd
Commentary
Social capital: theory, evidence, and implications for oral health
Patrick L. Rouxel1, Anja Heilmann1, Jun Aida2, Georgios Tsakos1 and Richard G. Watt1 1 Department of Epidemiology and Public Health, UCL, London, UK, 2Department of International and Community Oral Health, Tohoku University, Sendai, Japan
Rouxel PL, Heilmann A, Aida J, Tsakos G, Watt RG. Social capital: theory, evidence, and implications for oral health. Community Dent Oral Epidemiol 2015; 43: 97–105. © 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd Abstract – In the last two decades, there has been increasing application of the concept of social capital in various fields of public health, including oral health. However, social capital is a contested concept with debates on its definition, measurement, and application. This study provides an overview of the concept of social capital, highlights the various pathways linking social capital to health, and discusses the potential implication of this concept for health policy. An extensive and diverse international literature has examined the relationship between social capital and a range of general health outcomes across the life course. A more limited but expanding literature has also demonstrated the potential influence of social capital on oral health. Much of the evidence in relation to oral health is limited by methodological shortcomings mainly related to the measurement of social capital, cross-sectional study designs, and inadequate controls for confounding factors. Further research using stronger methodological designs should explore the role of social capital in oral health and assess its potential application in the development of oral health improvement interventions.
It is increasingly recognized within the international dental research community that oral diseases are determined by a range of interacting biological, psychological, behavioral, social, environmental, and political factors (1, 2). An emerging body of evidence is uncovering the key elements and pathways linking the broad distal determinants with the more proximal influences on oral health outcomes (3). In the fields of public health and the social sciences, considerable attention and debate has focused in recent decades on the concept of social capital and its potential application in social and health policy (4). Social capital has been highlighted as one of the key determinants of health in the WHO’s social determinants conceptual framework (5). For many decades, the importance of social relationships on health has been recognized (6) and a recent review has highlighted the significant influence of social relations on mortality, comparable to the effects of recognized behavioral factors such as smoking (7). doi: 10.1111/cdoe.12141
Key words: oral health; public health; social capital Richard G. Watt, Department of Epidemiology and Public Health, University College London, 1-19 Torrington Place, London WC1E 6BT, UK Tel.: 00 44 20 7679 1699 Fax: 00 44 20 7813 0280 e-mail: [email protected] Submitted 5 June 2014; accepted 1 December 2014
What is exactly meant by the term social capital and how does it differ from social support or social relationships? Is the evidence linking social capital to health robust and what are the potential implications of social capital for health improvement interventions? The aim of this study was to critically review the concept of social capital and to summarize the evidence on the association between social capital and both general and oral health. The study will also consider the potential implications of the concept for the future development of oral health improvement interventions.
Concepts, definitions, and measurement of social capital Contemporary concepts and definitions of social capital have been developed by a number of distinguished scholars and agencies such as Bourdieu (8), Coleman (9), Putnam (10, 11), and the OECD
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(12) (Table 1). In the field of public health, there are two distinct theories of social capital: a theory of social cohesion (communitarian approach) and a theory of social networks (individual approach) (13). Putnam (11) described social capital as a key characteristic of communities (rather than of individuals), defining it as ‘. . . social networks and the associated norms of reciprocity and trustworthiness that arise from them’. Putnam’s communitarian approach prioritizes the notion of social cohesion and focuses on social processes such as network formation, norms of reciprocity, and mutual trust, while the resources embedded within social networks are central to Bourdieu’s approach (14). Bourdieu’s theory acknowledges the existence of community social networks but emphasizes the individual’s ability to draw upon the resources within the social network in order to pursue their own individual goals, which may be different from the goals of the community. Even though these two approaches may not be mutually exclusive, public health research has almost exclusively relied on Putnam’s theory despite having received a variety of criticisms (15, 16). From a population health perspective, an important element of using the communitarian approach of social capital lies in redirecting the focus of attention away from the individual to the social structure in which they are embedded (17). Islam et al. (18) developed a useful typology of the different types of social capital (Fig. 1). Social capital can be broken down into cognitive and Table 1. Definitions of social capital Author
Definition
Bourdieu (8)
‘. . .the sum of resources, actual and virtual, that accrue to an individual or a group by virtue of possessing a durable network or less institutionalized relationships of mutual acquaintance and recognition’. ‘Social capital is defined by its function. It is not a single entity, but a variety of different entities, with two elements in common: they all consist of some aspect of social structures, and they facilitate certain actions of actors – whether persons or corporate actors – within the structure’. ‘. . . social networks and the associated norms of reciprocity and trustworthiness that arise from them’. ‘Networks together with shared norms, values and understandings that facilitate co-operation within or among groups’.
Coleman (9)
Putnam (11) OECD (12)
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structural elements. Cognitive social capital describes norms, values, perceptions, attitudes, and beliefs and is often measured via questions such as ‘Do you think most people can be trusted?’ Structural social capital refers to forms of social organization, such as network density, civic engagement, the functioning of institutions, and the rules and policies that govern society. Most authors further distinguish between different types of social capital, namely bonding and bridging (11), as well as linking (19, 20). Bonding social capital describes the strong bonds between members of a network who see themselves as being similar, such as family members, close friends, or neighbors. It is ‘inward looking’, with potentially negative effects when it is used to reinforce social class divides or to exclude minorities (11). Bridging social capital refers to the more distant and weaker ties between people who are in some sense different, with different access to resources, as such it is more ‘outward looking’ and inclusive. Harper (21) aptly described bonding social capital as a means of ‘getting by’ and bridging social capital as a means of ‘getting ahead’. The term ‘linking social capital’ has been introduced to characterize relationships between people who are interacting across formal power or authority gradients (20), indicating the degree of trust in governmental institutions. While bonding and bridging social capital operate horizontally, linking social capital connects people across vertical power differentials (18). Various validated research instruments have been developed to measure social capital including the UK Office for National Statistics harmonized set of questions (22); the World Bank’s Social Capital Tool (23) and the Adapted Social Capital Assessment Tool (24). A somewhat contentious issue is the question whether social capital is a characteristic of communities or individuals. Kawachi and colleagues (17) convincingly argue that it encompasses both: social capital resides in social structures such as communities or workplaces, and being a resource that individuals access through their social networks. Multilevel modeling has been extensively used to assess both individual and community-level effects. The lack of clarity regarding the definition and measurement of social capital has led to substantial criticism of the concept (25, 26). It has been argued that social capital adds little value and is difficult to distinguish from established concepts of social cohesion, social networks, and social support (27). However, the term ‘capital’ appeals
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Fig. 1. Forms and dimensions of social capital, and operationalization in empirical studies (18).
because it emphasizes the notion of ‘the social’ as a resource. Another argument brought forward is that the concept of social capital might be used to divert attention from the wider social determinants of health including social inequalities (25, 26). It certainly would be problematic to suggest that people in poor communities could be healthier if only they would be better at helping each other. Instead, it is important to emphasize that with increasing levels of inequality, social capital tends to deteriorate (28). Finally, there are the potential downsides to social capital – high levels of social capital among a subgroup or community might lead to social exclusion, restrictions on individual freedom, intolerance of minorities, or downward leveling of norms (18, 29). Despite these criticisms, social capital is a potentially useful concept that is of relevance in increasing our understanding of the broader determinants of health.
pathways linking social capital and oral health. The main mechanisms are (i) behavioral, (ii) psychosocial, (iii) via access to oral health services, and (iv) via policy development. Due to the complexity of the associations, Fig. 2 only displays pathways from social capital to oral health and does not display the potential feedback loops from oral health to social capital.
Behavioral pathways Social capital at both the community and individual levels may affect health behaviors through social norms and informal social control (peer pressure), and through the diffusion of health-related knowledge. For example, it has been shown that quitting smoking is strongly related to the smoking behaviors in a person’s peer network, and moreover, also to the behavior of strangers within a close social distance (30).
Psychosocial pathways
Hypothesized pathways linking social capital and oral health Drawing heavily on the work by Kawachi and Berkman (29), Fig. 2 depicts the hypothesized
High levels of social capital, for example within a neighborhood or a network of family and friends, are thought to have stress-buffering effects on health via access to social support, as well as via feelings of safety and belonging. There is some evidence that psychological distress influences oral
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Fig. 2. Pathways from social capital at the community and individual level to oral health outcomes.
health via allostatic load. Higher levels of stress hormones such as cortisol affect immune competence and thus lower the defense against oral bacteria, resulting in increased susceptibility to dental caries and periodontal disease (31, 32). Further, psychological distress can lead to coping mechanisms that involve health-compromising behaviors such as smoking and the consumption of comfort food high in sugars (33).
Access to dental care Communities with high levels of social capital in the form of civic engagement might be better able to lobby for access to high-quality health and social services. In addition, research suggests that social networks and social support play a role in promoting dental attendance (34, 35) and that persons who live alone or are unmarried use dental services less often than others (36).
Development of supportive public policy Finally, communities that are more cohesive produce more egalitarian patterns of political engagement that result in the development of more supportive health and social policies (29). Through the processes of community empowerment and engagement, social capital has the potential to mobilize the public as health advocates as a collective resource influencing political decision making and policy development at the local, regional, and national level.
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Social capital and health – evidence from empirical research Social capital and general health Since the mid-1990s, an extensive and diverse literature has examined the relationship between social capital and general health outcomes. In 2011 alone, over 2000 papers were published on the topic. To provide an overview of this burgeoning field of study, this section will present a brief summary of published reviews, systematic reviews, and meta-analyses on social capital and health. Support for beneficial effects of social capital is most consistent for mental health outcomes and self-rated health, while studies on associations with mortality, health behaviors, and health inequalities have so far produced mixed findings.
Mortality A review of prospective multilevel studies by Murayama et al. (37) included six studies which showed both positive as well as negative contextual effects of community-level social capital on all-cause mortality. The authors found the available research to be limited and noted considerable heterogeneity regarding the study settings and operationalization of social capital. Meijer et al. (38) reviewed different neighborhood factors in relation to mortality, separating studies on social capital and social cohesion
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despite conceptual overlap between the two concepts. Only one study on social capital was included, which found no association with mortality, while three studies reported associations between mortality and social cohesion. Most recently, Gilbert et al. (39) conducted a metaanalysis of nine studies on social capital and mortality outcomes, estimating that across the included studies, an average one-unit increase in social capital increased the odds of survival by 17 percent.
Self-rated health The aforementioned review by Murayama et al. (37) included two prospective multilevel studies on the effects on self-rated health, one in a community and one in a workplace setting, both of which found evidence for a positive association with social capital. The association with self-rated health was also assessed in the meta-analysis by Gilbert et al. (39), which summarized the effect sizes of 28 studies and calculated an average 29% increase in the odds of reporting good health for each one-unit increase in social capital.
Mental health A systematic review of 21 studies by De Silva et al. (40) concluded that individual-level social capital had protective effects on common mental disorders and child mental illness; however; the evidence in relation to community-level social capital was deemed inconclusive. Mair et al. (41) reviewed neighborhood characteristics in relation to depression, finding that 25 of 37 studies supported a link between depression and measures of neighborhood social processes including social capital and related concepts. Addressing a similar research question, Kim (42) in a review of 28 studies reported general support for associations between depression and neighborhood social disorder, but mixed findings for salutary effects of social capital. The latest systematic review by Nyqvist et al. (43) found that all 11 studies included showed a beneficial effect of social capital on mental health outcomes.
Health behaviors While not directly a health outcome, a significant part of the literature has focused on the links between social capital and health behaviors. A review by Samuel et al. (44) on several community-related social capital concepts and
health behaviors such as physical activity, smoking, and diet produced somewhat inconsistent results. However, trust between community members was consistently related to more health-promoting and less health-compromising behaviors. McPherson et al. (45) reviewed the associations between social capital and healthcompromising behaviors among younger people, concluding that social capital is ‘an important construct for understanding the establishment of health risk behaviors in young people’. The review found that positive parent-child relations were an important protective factor, while the role of peer-based social networks was more equivocal, that is, by some studies linked to an increased likelihood of risky behaviors.
Health inequalities Two systematic reviews examined the role of social capital on health inequalities. Uphoff et al. (46) found evidence of both a buffer and a dependency effect of social capital in relation to socioeconomic inequalities in health. The buffer hypothesis postulates that high levels of bonding social capital can alleviate the negative effects of social disadvantage by reducing stress. The dependency effect is based on the hypothesis that bridging social capital within a community is more accessible to those who are already better off, thus conferring an additional advantage (42). A second review by Vyncke et al. (47) focused on children and adolescents and produced mixed results, although a role of community social capital on the gradient in health was suggested.
Social capital and oral health So far no systematic reviews on social capital and oral health have been published; therefore, this section highlights the most important findings from well-designed empirical research. The databases Medline, Scopus, and ISI Web of Knowledge were used as search engines to investigate the literature on social capital and oral health published in English up until 2013. Key words used in the search included ‘social capital’, ‘social networks’, ‘social support’, ‘social relationships’, ‘caries’, ‘oral health’, ‘edentulism’, and ‘dental injuries’. Out of the 156 papers identified from this search strategy, 29 articles were selected based on the titles and abstracts. Twenty studies used individual-level measures of social capital, and nine studies used community-level measures in a multilevel framework. Studies
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were also included if they did not explicitly use the term ‘social capital’ but used closely related concepts such as social networks and support, social cohesion, and neighborhood trust.
Individual-level social capital and oral health among adults We identified 21 studies that reported positive associations between at least one individual-level measure of social capital (or related concepts) and better oral health outcomes among adults. Outcomes included number of remaining teeth, edentulism, dental visits, and denture status among older people (34, 48–54), dental caries (55–59), selfrated oral health (58, 60, 61), oral health-related quality of life (62, 63), periodontal disease (64–66), and dental pain (67). However, in nine of the above studies, the results were mixed, that is, not all aspects of social networks and support were associated with all of the examined oral health outcomes (34, 51–54, 58, 61, 65, 66). For example, having more close friends was associated with less decay but not with edentulism among older Americans (58), and in the same population, number of friends but not emotional support was associated with periodontal attachment loss (66). Among older Japanese, horizontal but not vertical social capital was related to dental status (52). One study found that the number of friends was associated with self-rated oral health only among the edentate; however, in this study, the models adjusted simultaneously for health-related behaviors which might have been on the pathway between social networks and oral health (61).
Individual-level social capital and oral health among children and adolescents Evidence on the association between individuallevel measures of social capital and oral health among children and adolescents is limited and inconsistent. One US study reported an association between the mother’s perceived social capital and her child’s unmet dental needs, but found no association with her rating of the child’s oral health (68). Another study from the US found no relationship between mothers’ perceived instrumental social support and their children’s caries status (69). In a Japanese study among university students, lower levels of neighborhood trust and vertical trust in high school (trust in teachers), but not trust/reciprocity among peers, were associated with poorer self-rated oral health (70).
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Community-level social capital and oral health among adults Community-level measures of social capital were associated with lower levels of dental caries among a sample of low income African Americans (56), as well as with lower odds of dental pain among Brazilian adults (67). However, three studies reported mixed findings. Community-level horizontal but not vertical social capital was associated with dental status among older Japanese (52). Another study on the same sample showed that while community-level mistrust was weakly associated with poor dental status, community social capital did not alleviate the association between income and dental status (71). In a different Japanese cohort of older people, only neighborhood friendship networks were related to dental status while other aspects of community social capital were not (53).
Community-level social capital and oral health among children and adolescents Two studies, one among Brazilian adolescents (72) and the other among Japanese preschool children (73) reported inverse associations between neighborhood empowerment/social cohesion and dental caries. Community social capital was also shown to be associated with fewer dental injuries among Brazilian adolescent boys (74). These findings are in contrast to another Brazilian study, which did not find a relationship between social cohesion and dental injury among 12-year-olds (75).
Summary and limitations of previous research A growing international literature has highlighted the potential influence of social capital on oral health among a diverse range of populations, at different points in the life course. However, it is important to acknowledge the limitations of the existing body of evidence in this area of investigation. Key limitations include the use of a wide and disparate range of different measures of social capital from community-level indicators of social capital such as perceptions of neighborhood safety, to proxy measures of social networks such as marital status. Only a limited number of studies have used longitudinal data. More advanced longitudinal analyses over extended time frames are needed to establish the temporal order between social capital and oral health, and to further explore the potential pathways. Finally, many studies have not adequately controlled for potentially confounding factors. As many oral health outcomes reflect accumulated life-course influences, confounders of the
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association between social capital and oral health such as socioeconomic position need to be accounted for across the life course.
Implications for health improvement and research Although an extensive international literature has focused on exploring the association between social capital and health, very few interventional studies have been conducted. Moore and colleagues (76) have assessed the methodological issues relating to the design, delivery, and evaluation of social capital measures. They highlighted how social capital interventions could focus on strengthening and developing individuals, organizations, and communities through action on the determinants of population health. Enhancing individual and/or community social capital could promote health and reduce inequalities through health literacy, psychosocial, behavioral, and policy mechanisms. Theory-driven interventions carefully tailored to the needs and characteristics of individuals and communities with robust evaluation and monitoring systems are fundamentally important. A recent review of social capital interventions identified a diverse range of studies targeting different population groups in a variety of settings in Brazil, Denmark, US, South Africa, and Japan (77). Overall these studies demonstrated positive effects in enhancing social capital and in improving various subjective health measures. Insights gained from the evaluation of these interventions highlighted three key issues. Firstly, the target population should not be too limited and narrow. Several of the interventions targeted older people living in the community but identified a ‘spillover effect’ across younger generations. Intergenerational effects would be a desirable outcome for such interventions. Second is the intervention unit size. Interventions that are too distant and removed from the subject’s familiar daily activities, interactions, and sense of community are less likely to have an impact. Local is best. Final key issue is the setting for the intervention. It appears more effective to utilize a place that subjects are already comfortable and familiar with as the setting for any intervention, rather than use a new setting that may alienate people. More research is undoubtedly needed to further explore the potential role of social capital on oral
health. Future research should use valid measures of social capital appropriate to the population group involved, longitudinal analyses, adequate control for confounding factors, and an investigation of the life-course pathways that link social capital and oral health. More interventional research is also needed which could include appropriate oral health outcomes.
Conclusion Emerging evidence indicates that social capital is associated with population health and well-being. Although the evidence in relation to oral health is less well developed, social capital appears as a potential social determinant of oral health. Further research using better measures of social capital, longitudinal study designs, and adequate controls for confounding factors is needed to explore in more depth the role of social capital on oral health.
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predominantly home-based and work-based networks. Health Qual Life Outcomes 2012;10:5. Sanders AE, Spencer AJ. Childhood circumstances, psychosocial factors and the social impact of adult oral health. Community Dent Oral Epidemiol 2005;33:370–7. Nicolau B, Netuveli G, Kim J-WM, Sheiham A, Marcenes W. A life-course approach to assess psychosocial factors and periodontal disease. J Clin Periodontol 2007;34:844–50. Merchant AT, Pitiphat W, Ahmed B, Kawachi I, Joshipura K. A prospective study of social support, anger expression and risk of periodontitis in men. J Am Dent Assoc 2003;134:1591–6. Sabbah W, Tsakos G, Chandola T, Newton T, Kawachi I, Sheiham A et al. The relationship between social network, social support and periodontal disease among older Americans. J Clin Periodontol 2011;38:547–52. Santiago BM, Valenca AM, Vettore MV. Social capital and dental pain in Brazilian northeast: a multilevel cross-sectional study. BMC Oral Health 2013;13:2. Iida H, Rozier RG. Mother-perceived social capital and children’s oral health and use of dental care in the United States. Am J Public Health 2013;103:480– 7. Finlayson TL, Siefert K, Ismail AI, Sohn W. Psychosocial factors and early childhood caries among low-income African-American children in Detroit. Community Dent Oral Epidemiol 2007;35:439–48. Furuta M, Ekuni D, Takao S, Suzuki E, Morita M, Kawachi I. Social capital and self-rated oral health among young people. Community Dent Oral Epidemiol 2011;40:97–104. Aida J, Kondo K, Kondo N, Watt RG, Sheiham A, Tsakos G. Income inequality, social capital and selfrated health and dental status in older Japanese. Soc Sci Med 2011;73:1561–8. Pattussi MP, Hardy R, Sheiham A. The potential impact of neighborhood empowerment on dental caries among adolescents. Community Dent Oral Epidemiol 2006;34:344–50. Aida J, Ando Y, Oosaka M, Niimi K, Morita M. Contributions of social context to inequality in dental caries: a multilevel analysis of Japanese 3-year-old children. Community Dent Oral Epidemiol 2008;36: 149–56. Pattussi MP, Hardy R, Sheiham A. Neighborhood social capital and dental injuries in Brazilian adolescents. Am J Public Health 2006;96:1462–8. Moyses SJ, Moyses ST, McCarthy M, Sheiham A. Intra-urban differentials in child dental trauma in relation to Healthy Cities policies in Curitiba, Brazil. Health & Place 2006;12:48–64. Moore S, Salsberg J, Leroux J. Advancing social capital interventions from a network and population health perspective. In: Kawachi I, Takeo S, Subramanian SV, editors. Global perspective on social capital and health. New York: Springler, 2013; 189–203. Murayama H, Kondo K, Fujiwara Y. Social capital interventions to promote healthy ageing. In: Kawachi I, Takeo S, Subramanian SV, editors. Global perspective on social capital and health. New York: Springer, 2013; 205–38.
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Commentary
Social capital: theory, evidence, and implications for oral health
Patrick L. Rouxel1, Anja Heilmann1, Jun Aida2, Georgios Tsakos1 and Richard G. Watt1 1 Department of Epidemiology and Public Health, UCL, London, UK, 2Department of International and Community Oral Health, Tohoku University, Sendai, Japan
Rouxel PL, Heilmann A, Aida J, Tsakos G, Watt RG. Social capital: theory, evidence, and implications for oral health. Community Dent Oral Epidemiol 2015; 43: 97–105. © 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd Abstract – In the last two decades, there has been increasing application of the concept of social capital in various fields of public health, including oral health. However, social capital is a contested concept with debates on its definition, measurement, and application. This study provides an overview of the concept of social capital, highlights the various pathways linking social capital to health, and discusses the potential implication of this concept for health policy. An extensive and diverse international literature has examined the relationship between social capital and a range of general health outcomes across the life course. A more limited but expanding literature has also demonstrated the potential influence of social capital on oral health. Much of the evidence in relation to oral health is limited by methodological shortcomings mainly related to the measurement of social capital, cross-sectional study designs, and inadequate controls for confounding factors. Further research using stronger methodological designs should explore the role of social capital in oral health and assess its potential application in the development of oral health improvement interventions.
It is increasingly recognized within the international dental research community that oral diseases are determined by a range of interacting biological, psychological, behavioral, social, environmental, and political factors (1, 2). An emerging body of evidence is uncovering the key elements and pathways linking the broad distal determinants with the more proximal influences on oral health outcomes (3). In the fields of public health and the social sciences, considerable attention and debate has focused in recent decades on the concept of social capital and its potential application in social and health policy (4). Social capital has been highlighted as one of the key determinants of health in the WHO’s social determinants conceptual framework (5). For many decades, the importance of social relationships on health has been recognized (6) and a recent review has highlighted the significant influence of social relations on mortality, comparable to the effects of recognized behavioral factors such as smoking (7). doi: 10.1111/cdoe.12141
Key words: oral health; public health; social capital Richard G. Watt, Department of Epidemiology and Public Health, University College London, 1-19 Torrington Place, London WC1E 6BT, UK Tel.: 00 44 20 7679 1699 Fax: 00 44 20 7813 0280 e-mail: [email protected] Submitted 5 June 2014; accepted 1 December 2014
What is exactly meant by the term social capital and how does it differ from social support or social relationships? Is the evidence linking social capital to health robust and what are the potential implications of social capital for health improvement interventions? The aim of this study was to critically review the concept of social capital and to summarize the evidence on the association between social capital and both general and oral health. The study will also consider the potential implications of the concept for the future development of oral health improvement interventions.
Concepts, definitions, and measurement of social capital Contemporary concepts and definitions of social capital have been developed by a number of distinguished scholars and agencies such as Bourdieu (8), Coleman (9), Putnam (10, 11), and the OECD
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(12) (Table 1). In the field of public health, there are two distinct theories of social capital: a theory of social cohesion (communitarian approach) and a theory of social networks (individual approach) (13). Putnam (11) described social capital as a key characteristic of communities (rather than of individuals), defining it as ‘. . . social networks and the associated norms of reciprocity and trustworthiness that arise from them’. Putnam’s communitarian approach prioritizes the notion of social cohesion and focuses on social processes such as network formation, norms of reciprocity, and mutual trust, while the resources embedded within social networks are central to Bourdieu’s approach (14). Bourdieu’s theory acknowledges the existence of community social networks but emphasizes the individual’s ability to draw upon the resources within the social network in order to pursue their own individual goals, which may be different from the goals of the community. Even though these two approaches may not be mutually exclusive, public health research has almost exclusively relied on Putnam’s theory despite having received a variety of criticisms (15, 16). From a population health perspective, an important element of using the communitarian approach of social capital lies in redirecting the focus of attention away from the individual to the social structure in which they are embedded (17). Islam et al. (18) developed a useful typology of the different types of social capital (Fig. 1). Social capital can be broken down into cognitive and Table 1. Definitions of social capital Author
Definition
Bourdieu (8)
‘. . .the sum of resources, actual and virtual, that accrue to an individual or a group by virtue of possessing a durable network or less institutionalized relationships of mutual acquaintance and recognition’. ‘Social capital is defined by its function. It is not a single entity, but a variety of different entities, with two elements in common: they all consist of some aspect of social structures, and they facilitate certain actions of actors – whether persons or corporate actors – within the structure’. ‘. . . social networks and the associated norms of reciprocity and trustworthiness that arise from them’. ‘Networks together with shared norms, values and understandings that facilitate co-operation within or among groups’.
Coleman (9)
Putnam (11) OECD (12)
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structural elements. Cognitive social capital describes norms, values, perceptions, attitudes, and beliefs and is often measured via questions such as ‘Do you think most people can be trusted?’ Structural social capital refers to forms of social organization, such as network density, civic engagement, the functioning of institutions, and the rules and policies that govern society. Most authors further distinguish between different types of social capital, namely bonding and bridging (11), as well as linking (19, 20). Bonding social capital describes the strong bonds between members of a network who see themselves as being similar, such as family members, close friends, or neighbors. It is ‘inward looking’, with potentially negative effects when it is used to reinforce social class divides or to exclude minorities (11). Bridging social capital refers to the more distant and weaker ties between people who are in some sense different, with different access to resources, as such it is more ‘outward looking’ and inclusive. Harper (21) aptly described bonding social capital as a means of ‘getting by’ and bridging social capital as a means of ‘getting ahead’. The term ‘linking social capital’ has been introduced to characterize relationships between people who are interacting across formal power or authority gradients (20), indicating the degree of trust in governmental institutions. While bonding and bridging social capital operate horizontally, linking social capital connects people across vertical power differentials (18). Various validated research instruments have been developed to measure social capital including the UK Office for National Statistics harmonized set of questions (22); the World Bank’s Social Capital Tool (23) and the Adapted Social Capital Assessment Tool (24). A somewhat contentious issue is the question whether social capital is a characteristic of communities or individuals. Kawachi and colleagues (17) convincingly argue that it encompasses both: social capital resides in social structures such as communities or workplaces, and being a resource that individuals access through their social networks. Multilevel modeling has been extensively used to assess both individual and community-level effects. The lack of clarity regarding the definition and measurement of social capital has led to substantial criticism of the concept (25, 26). It has been argued that social capital adds little value and is difficult to distinguish from established concepts of social cohesion, social networks, and social support (27). However, the term ‘capital’ appeals
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Fig. 1. Forms and dimensions of social capital, and operationalization in empirical studies (18).
because it emphasizes the notion of ‘the social’ as a resource. Another argument brought forward is that the concept of social capital might be used to divert attention from the wider social determinants of health including social inequalities (25, 26). It certainly would be problematic to suggest that people in poor communities could be healthier if only they would be better at helping each other. Instead, it is important to emphasize that with increasing levels of inequality, social capital tends to deteriorate (28). Finally, there are the potential downsides to social capital – high levels of social capital among a subgroup or community might lead to social exclusion, restrictions on individual freedom, intolerance of minorities, or downward leveling of norms (18, 29). Despite these criticisms, social capital is a potentially useful concept that is of relevance in increasing our understanding of the broader determinants of health.
pathways linking social capital and oral health. The main mechanisms are (i) behavioral, (ii) psychosocial, (iii) via access to oral health services, and (iv) via policy development. Due to the complexity of the associations, Fig. 2 only displays pathways from social capital to oral health and does not display the potential feedback loops from oral health to social capital.
Behavioral pathways Social capital at both the community and individual levels may affect health behaviors through social norms and informal social control (peer pressure), and through the diffusion of health-related knowledge. For example, it has been shown that quitting smoking is strongly related to the smoking behaviors in a person’s peer network, and moreover, also to the behavior of strangers within a close social distance (30).
Psychosocial pathways
Hypothesized pathways linking social capital and oral health Drawing heavily on the work by Kawachi and Berkman (29), Fig. 2 depicts the hypothesized
High levels of social capital, for example within a neighborhood or a network of family and friends, are thought to have stress-buffering effects on health via access to social support, as well as via feelings of safety and belonging. There is some evidence that psychological distress influences oral
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Fig. 2. Pathways from social capital at the community and individual level to oral health outcomes.
health via allostatic load. Higher levels of stress hormones such as cortisol affect immune competence and thus lower the defense against oral bacteria, resulting in increased susceptibility to dental caries and periodontal disease (31, 32). Further, psychological distress can lead to coping mechanisms that involve health-compromising behaviors such as smoking and the consumption of comfort food high in sugars (33).
Access to dental care Communities with high levels of social capital in the form of civic engagement might be better able to lobby for access to high-quality health and social services. In addition, research suggests that social networks and social support play a role in promoting dental attendance (34, 35) and that persons who live alone or are unmarried use dental services less often than others (36).
Development of supportive public policy Finally, communities that are more cohesive produce more egalitarian patterns of political engagement that result in the development of more supportive health and social policies (29). Through the processes of community empowerment and engagement, social capital has the potential to mobilize the public as health advocates as a collective resource influencing political decision making and policy development at the local, regional, and national level.
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Social capital and health – evidence from empirical research Social capital and general health Since the mid-1990s, an extensive and diverse literature has examined the relationship between social capital and general health outcomes. In 2011 alone, over 2000 papers were published on the topic. To provide an overview of this burgeoning field of study, this section will present a brief summary of published reviews, systematic reviews, and meta-analyses on social capital and health. Support for beneficial effects of social capital is most consistent for mental health outcomes and self-rated health, while studies on associations with mortality, health behaviors, and health inequalities have so far produced mixed findings.
Mortality A review of prospective multilevel studies by Murayama et al. (37) included six studies which showed both positive as well as negative contextual effects of community-level social capital on all-cause mortality. The authors found the available research to be limited and noted considerable heterogeneity regarding the study settings and operationalization of social capital. Meijer et al. (38) reviewed different neighborhood factors in relation to mortality, separating studies on social capital and social cohesion
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despite conceptual overlap between the two concepts. Only one study on social capital was included, which found no association with mortality, while three studies reported associations between mortality and social cohesion. Most recently, Gilbert et al. (39) conducted a metaanalysis of nine studies on social capital and mortality outcomes, estimating that across the included studies, an average one-unit increase in social capital increased the odds of survival by 17 percent.
Self-rated health The aforementioned review by Murayama et al. (37) included two prospective multilevel studies on the effects on self-rated health, one in a community and one in a workplace setting, both of which found evidence for a positive association with social capital. The association with self-rated health was also assessed in the meta-analysis by Gilbert et al. (39), which summarized the effect sizes of 28 studies and calculated an average 29% increase in the odds of reporting good health for each one-unit increase in social capital.
Mental health A systematic review of 21 studies by De Silva et al. (40) concluded that individual-level social capital had protective effects on common mental disorders and child mental illness; however; the evidence in relation to community-level social capital was deemed inconclusive. Mair et al. (41) reviewed neighborhood characteristics in relation to depression, finding that 25 of 37 studies supported a link between depression and measures of neighborhood social processes including social capital and related concepts. Addressing a similar research question, Kim (42) in a review of 28 studies reported general support for associations between depression and neighborhood social disorder, but mixed findings for salutary effects of social capital. The latest systematic review by Nyqvist et al. (43) found that all 11 studies included showed a beneficial effect of social capital on mental health outcomes.
Health behaviors While not directly a health outcome, a significant part of the literature has focused on the links between social capital and health behaviors. A review by Samuel et al. (44) on several community-related social capital concepts and
health behaviors such as physical activity, smoking, and diet produced somewhat inconsistent results. However, trust between community members was consistently related to more health-promoting and less health-compromising behaviors. McPherson et al. (45) reviewed the associations between social capital and healthcompromising behaviors among younger people, concluding that social capital is ‘an important construct for understanding the establishment of health risk behaviors in young people’. The review found that positive parent-child relations were an important protective factor, while the role of peer-based social networks was more equivocal, that is, by some studies linked to an increased likelihood of risky behaviors.
Health inequalities Two systematic reviews examined the role of social capital on health inequalities. Uphoff et al. (46) found evidence of both a buffer and a dependency effect of social capital in relation to socioeconomic inequalities in health. The buffer hypothesis postulates that high levels of bonding social capital can alleviate the negative effects of social disadvantage by reducing stress. The dependency effect is based on the hypothesis that bridging social capital within a community is more accessible to those who are already better off, thus conferring an additional advantage (42). A second review by Vyncke et al. (47) focused on children and adolescents and produced mixed results, although a role of community social capital on the gradient in health was suggested.
Social capital and oral health So far no systematic reviews on social capital and oral health have been published; therefore, this section highlights the most important findings from well-designed empirical research. The databases Medline, Scopus, and ISI Web of Knowledge were used as search engines to investigate the literature on social capital and oral health published in English up until 2013. Key words used in the search included ‘social capital’, ‘social networks’, ‘social support’, ‘social relationships’, ‘caries’, ‘oral health’, ‘edentulism’, and ‘dental injuries’. Out of the 156 papers identified from this search strategy, 29 articles were selected based on the titles and abstracts. Twenty studies used individual-level measures of social capital, and nine studies used community-level measures in a multilevel framework. Studies
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were also included if they did not explicitly use the term ‘social capital’ but used closely related concepts such as social networks and support, social cohesion, and neighborhood trust.
Individual-level social capital and oral health among adults We identified 21 studies that reported positive associations between at least one individual-level measure of social capital (or related concepts) and better oral health outcomes among adults. Outcomes included number of remaining teeth, edentulism, dental visits, and denture status among older people (34, 48–54), dental caries (55–59), selfrated oral health (58, 60, 61), oral health-related quality of life (62, 63), periodontal disease (64–66), and dental pain (67). However, in nine of the above studies, the results were mixed, that is, not all aspects of social networks and support were associated with all of the examined oral health outcomes (34, 51–54, 58, 61, 65, 66). For example, having more close friends was associated with less decay but not with edentulism among older Americans (58), and in the same population, number of friends but not emotional support was associated with periodontal attachment loss (66). Among older Japanese, horizontal but not vertical social capital was related to dental status (52). One study found that the number of friends was associated with self-rated oral health only among the edentate; however, in this study, the models adjusted simultaneously for health-related behaviors which might have been on the pathway between social networks and oral health (61).
Individual-level social capital and oral health among children and adolescents Evidence on the association between individuallevel measures of social capital and oral health among children and adolescents is limited and inconsistent. One US study reported an association between the mother’s perceived social capital and her child’s unmet dental needs, but found no association with her rating of the child’s oral health (68). Another study from the US found no relationship between mothers’ perceived instrumental social support and their children’s caries status (69). In a Japanese study among university students, lower levels of neighborhood trust and vertical trust in high school (trust in teachers), but not trust/reciprocity among peers, were associated with poorer self-rated oral health (70).
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Community-level social capital and oral health among adults Community-level measures of social capital were associated with lower levels of dental caries among a sample of low income African Americans (56), as well as with lower odds of dental pain among Brazilian adults (67). However, three studies reported mixed findings. Community-level horizontal but not vertical social capital was associated with dental status among older Japanese (52). Another study on the same sample showed that while community-level mistrust was weakly associated with poor dental status, community social capital did not alleviate the association between income and dental status (71). In a different Japanese cohort of older people, only neighborhood friendship networks were related to dental status while other aspects of community social capital were not (53).
Community-level social capital and oral health among children and adolescents Two studies, one among Brazilian adolescents (72) and the other among Japanese preschool children (73) reported inverse associations between neighborhood empowerment/social cohesion and dental caries. Community social capital was also shown to be associated with fewer dental injuries among Brazilian adolescent boys (74). These findings are in contrast to another Brazilian study, which did not find a relationship between social cohesion and dental injury among 12-year-olds (75).
Summary and limitations of previous research A growing international literature has highlighted the potential influence of social capital on oral health among a diverse range of populations, at different points in the life course. However, it is important to acknowledge the limitations of the existing body of evidence in this area of investigation. Key limitations include the use of a wide and disparate range of different measures of social capital from community-level indicators of social capital such as perceptions of neighborhood safety, to proxy measures of social networks such as marital status. Only a limited number of studies have used longitudinal data. More advanced longitudinal analyses over extended time frames are needed to establish the temporal order between social capital and oral health, and to further explore the potential pathways. Finally, many studies have not adequately controlled for potentially confounding factors. As many oral health outcomes reflect accumulated life-course influences, confounders of the
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association between social capital and oral health such as socioeconomic position need to be accounted for across the life course.
Implications for health improvement and research Although an extensive international literature has focused on exploring the association between social capital and health, very few interventional studies have been conducted. Moore and colleagues (76) have assessed the methodological issues relating to the design, delivery, and evaluation of social capital measures. They highlighted how social capital interventions could focus on strengthening and developing individuals, organizations, and communities through action on the determinants of population health. Enhancing individual and/or community social capital could promote health and reduce inequalities through health literacy, psychosocial, behavioral, and policy mechanisms. Theory-driven interventions carefully tailored to the needs and characteristics of individuals and communities with robust evaluation and monitoring systems are fundamentally important. A recent review of social capital interventions identified a diverse range of studies targeting different population groups in a variety of settings in Brazil, Denmark, US, South Africa, and Japan (77). Overall these studies demonstrated positive effects in enhancing social capital and in improving various subjective health measures. Insights gained from the evaluation of these interventions highlighted three key issues. Firstly, the target population should not be too limited and narrow. Several of the interventions targeted older people living in the community but identified a ‘spillover effect’ across younger generations. Intergenerational effects would be a desirable outcome for such interventions. Second is the intervention unit size. Interventions that are too distant and removed from the subject’s familiar daily activities, interactions, and sense of community are less likely to have an impact. Local is best. Final key issue is the setting for the intervention. It appears more effective to utilize a place that subjects are already comfortable and familiar with as the setting for any intervention, rather than use a new setting that may alienate people. More research is undoubtedly needed to further explore the potential role of social capital on oral
health. Future research should use valid measures of social capital appropriate to the population group involved, longitudinal analyses, adequate control for confounding factors, and an investigation of the life-course pathways that link social capital and oral health. More interventional research is also needed which could include appropriate oral health outcomes.
Conclusion Emerging evidence indicates that social capital is associated with population health and well-being. Although the evidence in relation to oral health is less well developed, social capital appears as a potential social determinant of oral health. Further research using better measures of social capital, longitudinal study designs, and adequate controls for confounding factors is needed to explore in more depth the role of social capital on oral health.
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