Abstracts

Introduction

Oral health is more than the absence of disease and necessarily includes patient-reported outcome measures such as oral-health related quality of life (OHRQoL) ¹1. Glick M, Williams DM, Kleinman DV, Vujicic M, Watt RG, Weyant RJ. A new definition for oral health developed by the FDI World Dental Federation opens the door to a universal definition of oral health. Am J Orthod Dentofacial Orthop 2017; 151:229-31.^,22. Slade GD, editor. Measuring oral health and quality of life. Chapel Hill: School of Dentistry, University of North Carolina; 1997., as clinical measures are not sufficient to describe health. To assess the variability of OHRQoL, studies have evaluated the effects of stress ³3. Gupta E, Robinson PG, Marya CM, Baker SR. Oral health inequalities: relationships between environmental and individual factors. J Dent Res 2015; 94:1362-8., depressive symptoms ⁴4. Kressin NR, Spiro 3rd A, Atchison KA, Kazis L, Jones JA. Is depressive symptomatology associated with worse oral functioning and well-being among older adults? J Public Health Dent 2002; 62:5-12.^,55. Noguchi S, Makino M, Haresaku S, Shimada K, Naito T. Insomnia and depression impair oral health-related quality of life in the old-old. Geriatr Gerontol Int 2017; 17:893-7. and support from social networks ³3. Gupta E, Robinson PG, Marya CM, Baker SR. Oral health inequalities: relationships between environmental and individual factors. J Dent Res 2015; 94:1362-8.^,44. Kressin NR, Spiro 3rd A, Atchison KA, Kazis L, Jones JA. Is depressive symptomatology associated with worse oral functioning and well-being among older adults? J Public Health Dent 2002; 62:5-12.^,55. Noguchi S, Makino M, Haresaku S, Shimada K, Naito T. Insomnia and depression impair oral health-related quality of life in the old-old. Geriatr Gerontol Int 2017; 17:893-7.^,66. Gabardo MCL, Moysés SJ, Moysés ST, Olandoski M, Olinto MTA, Pattussi MP. Multilevel analysis of self-perception in oral health and associated factors in Southern Brazilian adults: a cross-sectional study. Cad Saúde Pública 2015; 31:49-59.^,77. Guedes RS, Piovesan C, Antunes JLF, Mendes FM, Ardenghi TM. Assessing individual and neighborhood social factors in child oral health-related quality of life: a multilevel analysis. Qual Life Res 2014; 23:2521-30.^,88. Lindmark U, Hakeberg M, Hugoson A. Sense of coherence and oral health status in an adult Swedish population. Acta Odontol Scand 2011; 69:12-20.^,99. Thomson WM, Caspi A, Poulton R, Moffitt TE, Broadbent JM. Personality and oral health. Eur J Oral Sci 2011; 119:366-72..

In 2010, USD 2.5 trillion was lost worldwide due to work-related disorders associated with psychological stress and related problems ¹⁰10. Bloom DE, Cafiero E, Jané-Llopis E, Abrahams-Gessel S, Bloom LR, Fathima S, et al. The global economic burden of noncommunicable diseases. Geneva: World Economic Forum; 2011. (PGDA Working Papers).. Psychological stress occurs due to excessive demands related to the environment, life and work of the affected individuals ¹¹11. Cooper C, Dewe P, O'Driscoll M. Organizational stress: a review and critique of theory, research, and applications. Thousand Oaks: SAGE Publications; 2012.. The person-context relation is dynamic, as the social environment is constantly changing, posing new demands and requiring continuous adaptability ¹²12. Hanson BS, Liedberg B, Öwall B. Social network, social support and dental status in elderly Swedish men. Community Dent Oral Epidemiol 1994; 22(5 Pt 1):331-7., which can result in chronic stress. This condition can impact OHRQoL ³3. Gupta E, Robinson PG, Marya CM, Baker SR. Oral health inequalities: relationships between environmental and individual factors. J Dent Res 2015; 94:1362-8.^,99. Thomson WM, Caspi A, Poulton R, Moffitt TE, Broadbent JM. Personality and oral health. Eur J Oral Sci 2011; 119:366-72. by causing individuals to engage in adverse health behaviors ¹³13. Marshall LL, Allison A, Nykamp D, Lanke S. Perceived stress and quality of life among doctor of pharmacy students. Am J Pharm Educ 2008; 72:137.^,1414. Okoro CA, Strine TW, Eke PI, Dhingra SS, Balluz LS. The association between depression and anxiety and use of oral health services and tooth loss. Community Dent Oral Epidemiol 2012; 40:134-44.^,1515. Sekiguchi A, Kawashiri S-Y, Hayashida H, Nagaura Y, Nobusue K, Nonaka F, et al. Association between high psychological distress and poor oral health-related quality of life (OHQoL) in Japanese community-dwelling people: the Nagasaki Islands Study. Environ Health Prev Med 2020; 25:82.^,1616. Karademas EC. Self-efficacy, social support and well-being: the mediating role of optimism. Pers Individ Dif 2006; 40:1281-90. such as alcohol consumption, smoking, and lower use of health services.

Discrimination is a highly stressful event that marginalized groups often face ¹⁷17. Wong CF, Schrager SM, Holloway IW, Meyer IH, Kipke MD. Minority stress experiences and psychological well-being: the impact of support from and connection to social networks within the Los Angeles House and Ball communities. Prev Sci 2014; 15:44-55.^,1818. Gee GC, Payne-Sturges DC. Environmental health disparities: a framework integrating psychosocial and environmental concepts. Environ Health Perspect 2004; 112:1645.. People who are entitled to government benefits are particularly exposed to stigma and prejudice ¹⁹19. Layton ML. Welfare stereotypes and conditional cash transfer programmes: evidence from Brazil's Bolsa Família. Journal of Politics in Latin America 2020; 12:53-76., experiencing stressors that affect their psychological and physiological health ²⁰20. Bastos JL, Celeste RK, Silva DAS, Priest N, Paradies YC. Assessing mediators between discrimination, health behaviours and physical health outcomes: a representative cross-sectional study. Soc Psychiatry Psychiatr Epidemiol 2015; 50:1731-42.. A systematic review found an association between perceived discrimination and poor mental health, indicating that the impacts of discrimination on physical health are likely mediated by stress responses ²¹21. Pascoe EA, Smart Richman L. Perceived discrimination and health: a meta-analytic review. Psychol Bull 2009; 135:531-54.. Similarly, chronic stress has been identified as a mediator of the relationship between discrimination and mental health ²⁰20. Bastos JL, Celeste RK, Silva DAS, Priest N, Paradies YC. Assessing mediators between discrimination, health behaviours and physical health outcomes: a representative cross-sectional study. Soc Psychiatry Psychiatr Epidemiol 2015; 50:1731-42..

Social support networks may increase individuals’ abilities to deal with the negative effects of stress on health ⁴4. Kressin NR, Spiro 3rd A, Atchison KA, Kazis L, Jones JA. Is depressive symptomatology associated with worse oral functioning and well-being among older adults? J Public Health Dent 2002; 62:5-12.^,1515. Sekiguchi A, Kawashiri S-Y, Hayashida H, Nagaura Y, Nobusue K, Nonaka F, et al. Association between high psychological distress and poor oral health-related quality of life (OHQoL) in Japanese community-dwelling people: the Nagasaki Islands Study. Environ Health Prev Med 2020; 25:82.^,1717. Wong CF, Schrager SM, Holloway IW, Meyer IH, Kipke MD. Minority stress experiences and psychological well-being: the impact of support from and connection to social networks within the Los Angeles House and Ball communities. Prev Sci 2014; 15:44-55.^,2222. Berkman LF, Glass T. Social integration, social networks, social support, and health. In: Berkman LF, Kawachi I, editors. Social epidemiology. New York: Oxford University Press; 2000. p. 137-73.. There is an association between support from social networks and lower morbidity and mortality rates ²²22. Berkman LF, Glass T. Social integration, social networks, social support, and health. In: Berkman LF, Kawachi I, editors. Social epidemiology. New York: Oxford University Press; 2000. p. 137-73.^,2323. Seeman TE. Social ties and health: the benefits of social integration. Ann Epidemiol 1996; 6:442-51., better oral health ³3. Gupta E, Robinson PG, Marya CM, Baker SR. Oral health inequalities: relationships between environmental and individual factors. J Dent Res 2015; 94:1362-8.^,1212. Hanson BS, Liedberg B, Öwall B. Social network, social support and dental status in elderly Swedish men. Community Dent Oral Epidemiol 1994; 22(5 Pt 1):331-7.^,2424. Lamarca GA, Leal MC, Leao ATT, Sheiham A, Vettore MV. The different roles of neighbourhood and individual social capital on oral health-related quality of life during pregnancy and postpartum: a multilevel analysis. Community Dent Oral Epidemiol 2014; 42:139-50., lower stress levels, and greater psychological well-being ¹⁷17. Wong CF, Schrager SM, Holloway IW, Meyer IH, Kipke MD. Minority stress experiences and psychological well-being: the impact of support from and connection to social networks within the Los Angeles House and Ball communities. Prev Sci 2014; 15:44-55.. Social support networks include the social relationships that each person maintains with others, such as intimate connections with family members and friends and formal relationships with external groups ²³23. Seeman TE. Social ties and health: the benefits of social integration. Ann Epidemiol 1996; 6:442-51.. They can have different implications, including the provision of social support among members ²⁵25. Due P, Holstein B, Lund R, Modvig J, Avlund K. Social relations: network, support and relational strain. Soc Sci Med 1999; 48:661-73.^,2626. O'Reilly P. Methodological issues in social support and social network research. Soc Sci Med 1988; 26:863-73.. Social support includes qualitative dimensions of the social networks ²⁵25. Due P, Holstein B, Lund R, Modvig J, Avlund K. Social relations: network, support and relational strain. Soc Sci Med 1999; 48:661-73., which interact with other factors via psychological and behavioral mechanisms ²²22. Berkman LF, Glass T. Social integration, social networks, social support, and health. In: Berkman LF, Kawachi I, editors. Social epidemiology. New York: Oxford University Press; 2000. p. 137-73.. Increased social support is associated with a reduced effect of discrimination on mental health among marginalized groups ²¹21. Pascoe EA, Smart Richman L. Perceived discrimination and health: a meta-analytic review. Psychol Bull 2009; 135:531-54.. Individuals with greater social networks are more likely to quit smoking and seek dental care more frequently ²⁷27. Rickardsson B, Hanson BS. Social network and regular dental care utilisation in elderly men. Results from the population study »,» ®,® §,§ ­,­ ¹,¹ ²,² ³,³ ß,ß Þ,Þ þ,þ ×,× Ú,Ú ú,ú Û,Û û,û Ù,Ù ù,ù ¨,¨ Ü,Ü ü,ü Ý,Ý ý,ý ¥,¥ ÿ,ÿ ¶,¶ Men born in 1914 »,» ®,® §,§ ­,­ ¹,¹ ²,² ³,³ ß,ß Þ,Þ þ,þ ×,× Ú,Ú ú,ú Û,Û û,û Ù,Ù ù,ù ¨,¨ Ü,Ü ü,ü Ý,Ý ý,ý ¥,¥ ÿ,ÿ ¶,¶ , Malmö, Sweden. Swed Dent J 1989; 13:151-61.^,2828. Hanson BS, Isacsson SO, Janzon L, Lindell SE. Social support and quitting smoking for good. Is there an association? Results from the population study, »,» ®,® §,§ ­,­ ¹,¹ ²,² ³,³ ß,ß Þ,Þ þ,þ ×,× Ú,Ú ú,ú Û,Û û,û Ù,Ù ù,ù ¨,¨ Ü,Ü ü,ü Ý,Ý ý,ý ¥,¥ ÿ,ÿ ¶,¶ Men born in 1914 »,» ®,® §,§ ­,­ ¹,¹ ²,² ³,³ ß,ß Þ,Þ þ,þ ×,× Ú,Ú ú,ú Û,Û û,û Ù,Ù ù,ù ¨,¨ Ü,Ü ü,ü Ý,Ý ý,ý ¥,¥ ÿ,ÿ ¶,¶ , Malmö, Sweden. Addict Behav 1990; 15:221-33.. Material support from social support networks also seems to weaken the association between discriminatory experiences and alcohol abuse ²¹21. Pascoe EA, Smart Richman L. Perceived discrimination and health: a meta-analytic review. Psychol Bull 2009; 135:531-54.. Nonetheless, having close friends who consume alcohol, tobacco and marijuana is associated with greater chances of using these substances ²⁹29. Musher-Eizenman DR, Holub SC, Arnett M. Attitude and peer influences on adolescent substance use: the moderating effect of age, sex, and substance. J Drug Educ 2003; 33:1-23.^,3030. Lau-Barraco C, Collins RL. Social networks and alcohol use among nonstudent emerging adults: a preliminary study. Addict Behav 2011; 36:47-54., as well as ultra-processed foods ³¹31. Ali MM, Amialchuk A, Heiland FW. Weight-related behavior among adolescents: the role of peer effects. PLoS One 2011; 6:e21179..

Based on the current understanding of these mechanisms, there might be an indirect relationship between social support and oral health, mediated by self-efficacy, that is, the belief an individual has in their capacity to deal with stressful situations ³²32. Miao L, Feng J, Wu L, Zhang S, Ge Z, Pan Y. The mediating role of general self-efficacy in the association between perceived social support and oral health-related quality of life after initial periodontal therapy. BMC Oral Health 2016; 16:68.. Social support networks may help people cope with stressful events and serve as a buffer against their negative impacts on oral health. A longitudinal study found that social support networks reduced stress levels and their impacts on OHRQoL ³3. Gupta E, Robinson PG, Marya CM, Baker SR. Oral health inequalities: relationships between environmental and individual factors. J Dent Res 2015; 94:1362-8.. Limited support from social networks and high levels of psychological stress are associated with the adoption of unhealthy behaviors such as the consumption of alcohol and tobacco ¹³13. Marshall LL, Allison A, Nykamp D, Lanke S. Perceived stress and quality of life among doctor of pharmacy students. Am J Pharm Educ 2008; 72:137.^,1515. Sekiguchi A, Kawashiri S-Y, Hayashida H, Nagaura Y, Nobusue K, Nonaka F, et al. Association between high psychological distress and poor oral health-related quality of life (OHQoL) in Japanese community-dwelling people: the Nagasaki Islands Study. Environ Health Prev Med 2020; 25:82.^,2929. Musher-Eizenman DR, Holub SC, Arnett M. Attitude and peer influences on adolescent substance use: the moderating effect of age, sex, and substance. J Drug Educ 2003; 33:1-23.^,3030. Lau-Barraco C, Collins RL. Social networks and alcohol use among nonstudent emerging adults: a preliminary study. Addict Behav 2011; 36:47-54.. Moreover, it has been postulated that when two or more factors (e.g., psychological stress and support from social networks) affect a health condition (e.g., OHRQoL) by the same mechanism (e.g., health behaviors and missing teeth), they can interact by antagonism or synergy ³³33. Knol MJ, VanderWeele TJ. Recommendations for presenting analyses of effect modification and interaction. Int J Epidemiol 2012; 41:514-20.^,3434. Rothman KJ. Synergy and antagonism in cause-effect relationships. Am J Epidemiol 1974; 99:385-8.: one factor can modify the effect of another (Figure 1). Although plausible, the hypothesis that social support networks interact with discrimination and stress by antagonism has not yet been well investigated; previous studies with adults and schoolchildren have shown that indicators of social capital reduced the effect of perceived stress on oral health ³⁵35. Hensel ALJ, Gomaa N. Social and economic capital as effect modifiers of the association between psychosocial stress and oral health. PLoS One 2023; 18:e0286006. and that the sense of coherence reduced the effect of perceived discrimination on quality of life ³⁶36. Noronha TG, Knorst JK, Godois LS, Emmanuelli B, Ardenghi TM, Tomazoni F. Sense of coherence moderates the relationship between perceived racial discrimination and oral health-related quality of life in schoolchildren. J Dent 2023; 131:104432..

This study aims to: (1) examine the associations between psychological stress, discrimination, and oral health-related quality of life; and (2) assess whether social support, stress and discrimination interact to modify their associations with OHRQoL.

Methods

This is a cross-sectional household-based study carried out in the city of São Leopoldo, Rio Grande do Sul State, Brazil. The 2010 Demographic Census reported that the city had 64,561 resident families, and the target population consisted of the 17,922 families registered in the municipality’s Unified Register, which is used to obtain several social benefits. According to the register, 6,086 families received the Brazilian Income Transfer Program benefit and another 1,852 families were eligible for it but were not beneficiaries, totaling 7,938 families eligible for this study in 2016. Data were collected from November 2016 to August 2018; methodological information and quality control procedures were described in a previous study ³⁷37. Ritzel IF, Pinheiro LS, Hugo FN, Hilgert JB, Bastos JL, Celeste RK. Inequalities in use of dental services and sociodemographic characteristics 6 among a eligible population for Bolsa Família in a city of south Brazil. Cad Saúde Colet (Rio J.); in press.. The sample size was estimated to evaluate the difference in the prevalence of self-reported dental pain between the groups of people with and without the Brazilian Income Transfer Program benefit. Based on previous information, a sample of 767 individuals nested in 143 households was deemed necessary for each group, as everyone in the household would be included. Simple random selection was carried out using addresses provided by the Unified Register, and all data were collected in person by trained interviewers, using a standardized questionnaire administered at the respondents’ homes. Only respondents aged 14 or over were included in the analysis. The study was approved by the Research Ethics Committee of the Federal University of Rio Grande do Sul (UFRGS; protocol n. 1,269,053), in accordance with the principles of the Declaration of Helsinki.

Outcome variable

OHRQoL was assessed with the Oral Impacts on Daily Performance (OIDP-9) scale, which contains nine items that measure the impact of oral conditions on daily activities, including physical, psychological, and social dimensions ³⁸38. Pilotto LM, Scalco GPC, Abegg C, Celeste RK. Factor analysis of two versions of the Oral Impacts on Daily Performance scale. Eur J Oral Sci 2016; 124:272-8.. The instrument has acceptable psychometric properties for use among adults ³⁹39. Adulyanon S, Vourapukjaru J, Sheiham A. Oral impacts affecting daily performance in a low dental disease Thai population. Community Dent Oral Epidemiol 1996; 24:385-9.^,4040. Adulyanon S, Sheiham A. Oral Impacts on Daily Performances. In: Slade G, editor. Measuring oral health and quality of life. Chapel Hill: School of Dentistry, University of North Carolina; 1997. p. 152-60. and adolescents ⁴¹41. Åstrøm AN, Okullo I. Validity and reliability of the Oral Impacts on Daily Performance (OIDP) frequency scale: a cross-sectional study of adolescents in Uganda. BMC Oral Health 2003; 3:5.. In the current analysis, the scale score was dichotomized into two results - OIDP = 0 and OIDP > 0 - in order to estimate the prevalence of the impacts, as suggested by Tsakos et al. ⁴²42. Tsakos G, Allen PF, Steele JG, Locker D. Interpreting oral health-related quality of life data. Community Dent Oral Epidemiol 2012; 40:193-200..

Main exposure variables

Three variables were studied as main exposures. Psychological stress was assessed using the Perceived Stress Scale (PSS-14) ⁴³43. Luft CB, Sanches SO, Mazo GZ, Andrade A. versão brasileira da Escala de Estresse Percebido: tradução e validação para idosos. Rev Saúde Pública 2007; 41:606-15.^,4444. Cohen S, Kamarck T, Mermelstein R. A global measure of perceived stress. J Health Soc Behav 1983; 24:385-96., which evaluates how individuals perceive stressful daily experiences. The PSS-14 has 14 questions with answers ranging from 0 to 4 (0 = never; 1 = almost never; 2 = sometimes; 3 = almost always; 4 = always). The final score ranges from 0 to 56, and higher values indicate higher stress. Final PSS scores were dichotomized into PSS < 39 and PSS ≥ 39 for analytical purposes.

Social support networks were evaluated based on the number of close relatives or friends of the participants, assessed using the following questions: “How many relatives do you feel comfortable with and can talk to about almost anything?” and “How many friends do you feel comfortable with and can talk to about almost anything?”; for which the possible answers were: none; one to two; three or more. For analytical purposes, the questions were combined, and participants were considered to have extensive social networks if they had three or more friends or relatives and to have limited social networks if they did not.

Discrimination was measured with a short version of the Everyday Discrimination Scale⁴⁵45. Williams DR, Yu Y, Jackson JS, Anderson NB. Racial differences in physical and mental health: socio-economic status, stress and discrimination. J Health Psychol 1997; 2:335-51., which includes five dichotomous (yes, no) questions related to discriminatory experiences that may have occurred in the previous six months in/at: (1) the workplace; (2) home; (3) school/university; (4) interactions with police officers or security guards; and (5) public spaces. A follow-up question addressed the possible grounds for discrimination, including race/skin color, sex, religion, and socioeconomic status. In this study, any episode of discrimination reported in response to any question was considered as exposure to discrimination.

Covariates

Five exogenous variables were included in the analysis as confounding factors (Figure 1). Sex (female, male), age (continuous variable later divided into three categories: 15-24, 25-44, ≥ 45, in years), race/skin color (dichotomized into two categories: white, non-white), education level (incomplete primary education, incomplete secondary education, complete secondary or tertiary education), and economic class, defined based on a set of household assets and divided into the following categories according to the Brazilian Economic Classification Criteria (Brazilian Association of Research Companies - ABEP): E (very low), D (low), C2 (lower middle) and C1 (middle).

The self-reported number of missing teeth was considered a mediator (Figure 1) and assessed with two questions, each referring to one jaw (upper or lower). Respondents were asked “Considering that a person has 16 teeth in the upper/lower jaw, how many teeth have you lost?”. The number of missing teeth in the upper and lower jaw were summed up, and the resulting variable was divided into three categories: 0-4, 5-27, and 28-32 missing teeth.

Statistical analysis

The absolute and relative frequencies of OIDP > 0 were computed according to covariates and main exposures. Comparisons were presented and statistically tested with the chi-square test, incorporating the cluster effect, given that households were the primary sampling unit. Multiple logistic regression analysis was also performed to assess independent associations between covariates and exposure variables, stratified by two social network groups (extensive and limited). Odds ratios (OR) and 95% confidence intervals (95%CI) were estimated using two regression models. The results of the initial full model and a final model are presented in this article. The initial model included all interactions and the final model consisted of an adjusted analysis, including only the interactions and variables with p ≤ 0.10. The following interactions between variables of interest were estimated: (1) extensive social networks and high level of stress; (2) extensive social networks and discrimination; and (3) discrimination and high level of stress.

In addition to the interactions estimated by regression, the relative excess of risk due to interaction (RERI) was calculated as a departure from additivity of effects (prevalence scale). The RERI is a measure of interaction that reflects the proportional excess of risk/prevalence between the observed and expected proportions of a disease in a group exposed to both risk factors ³³33. Knol MJ, VanderWeele TJ. Recommendations for presenting analyses of effect modification and interaction. Int J Epidemiol 2012; 41:514-20.. All analyses were carried out using Stata software, version 16.1 (https://www.stata.com).

Results

Over 410 addresses obtained from the Unified Register were contacted. Of these, 260 were valid, and 180 heads of household agreed to participate, which totaled 658 individuals. In total, 452 individuals aged 14 years and over were included in the analysis; however, due to missing data, the final analytical sample comprised 396 participants.

Table 1 shows that most participants in the sample were women (59.6%), aged from 25-44 years (42.2%), white (52.5%), and had complete secondary education (48.5%). While 12.4% of the participants reported experiencing high levels of psychological stress, 52.8% had limited social networks. The prevalence of oral impacts among women and men was 72.7% and 60%, respectively (p < 0.01). The prevalence of OIDP > 0 was 81.6% among participants who reported experiencing high levels of stress and 65.5% among those who reported experiencing lower levels of stress (p < 0.01). The prevalence of OIDP > 0 was 69.1% among people with limited social networks, but fell to 66.1% among those with extensive social networks (p = 0.53). Lastly, the prevalence of OIDP > 0 was 78.9% among those who reported experiencing discrimination and 61.1% among those who did not (p < 0.01).

Tables 2 and 3 show stratified analyses by social support networks with the interactions. In the group with limited networks, there was a difference of 22.5 percentage points in the prevalence of oral impacts (OIDP > 0) between participants who reported experiencing low and high levels of stress (65.5% and 87.9%, respectively, p < 0.01, Tables 2 and 3). In contrast, a difference of 2.9 percentage points was observed between these groups when including only participants with extensive networks (65.9% and 68.8% for low and high levels of stress, respectively, p = 0.82). There was a non-statistically significant interaction by antagonism between higher levels of stress and extensive networks considering RERI = -0.30 (95%CI: -0.72; -0.12), which means that the observed prevalence was 30% lower than expected among the doubly exposed group.

Among individuals with limited social networks, 76.9% of those who experienced discrimination reported feeling some impact on daily performances, but only 64.3% of those who did not report experiencing discrimination felt this impact (p < 0.01) (Tables 2 and 3). In the subgroup with extensive networks, the prevalence of impacts (OIDP > 0) among those who reported and did not report experiencing discrimination was 81.3% and 58.2%, respectively (p < 0.01). Interaction indicators pointed to additive synergy: the prevalence of impacts in the doubly exposed group was 16% higher than expected, with a RERI = 0.16 (95%CI: -0.12; -0.43, after adjustment for age and sex, Table 3).

Table 3 shows the prevalence of OIDP > 0 according to stress and discrimination. In the group that reported a lower level of stress, 75.4% of those who experienced discrimination reported feeling some impact on daily performance, but only 60.4% of those who did not experience discrimination reported feeling this impact (p < 0.01) (Table 3). Among individuals experiencing high levels of stress, the prevalence of impacts (OIDP > 0) in those who reported and did not report discrimination was, respectively, 95.8% and 68% (p < 0.01). The interaction indicator pointed to additive synergy: the prevalence of impacts in the doubly exposed group was 26% higher than expected, with a RERI = 0.26 (95%CI: -0.10; -0.61, after adjustment for age and sex, Table 3).

Table 4 shows the results of the regression models. The initial full model included three joint interactions, and the final model only retained variables with p ≤ 0.10. The final model revealed that women were more likely to report an impact on OIDP (OR = 1.77, 95%CI: 1.13; 2.76). There were interaction terms between discrimination and stress, with p = 0.09. Among individuals with lower levels of stress, those who reported discrimination were found to have higher odds (OR = 2.03, 95%CI: 1.23; 3.34) of experiencing OIDP; among those with higher levels of stress, discrimination was associated with an OR = 12.6 (95%CI: 1.31; 120.9) for OIDP. Fit indicators showed that the final model with one interaction (Bayesian information criterion - BIC = 499.7) was better than the full initial model with three interactions (BIC = 521.5).

Discussion

Our findings indicate that there is an association between discrimination and high levels of psychological stress and OIDP. Additionally, we found a significant synergistic interaction between psychological stress and discrimination and OIDP. The presence of extensive social support networks resulted in inconclusive results that were not statistically significant; some results indicated that extensive social support networks interacted by antagonism with stress and by synergy with discrimination. The adjusted regression models did not support the proposed protective effect of extensive social networks on oral health related quality of life.

The lack of association between social support networks and OHRQoL in this sample differs from the current literature that reports that social support networks contributes to better oral health ³3. Gupta E, Robinson PG, Marya CM, Baker SR. Oral health inequalities: relationships between environmental and individual factors. J Dent Res 2015; 94:1362-8.^,1212. Hanson BS, Liedberg B, Öwall B. Social network, social support and dental status in elderly Swedish men. Community Dent Oral Epidemiol 1994; 22(5 Pt 1):331-7.^,2424. Lamarca GA, Leal MC, Leao ATT, Sheiham A, Vettore MV. The different roles of neighbourhood and individual social capital on oral health-related quality of life during pregnancy and postpartum: a multilevel analysis. Community Dent Oral Epidemiol 2014; 42:139-50. and also differs from a study that showed that social capital can reduce the effect of psychological stress on oral health ³⁵35. Hensel ALJ, Gomaa N. Social and economic capital as effect modifiers of the association between psychosocial stress and oral health. PLoS One 2023; 18:e0286006.. People who have extensive social networks were also found to be more likely to report psychological well-being and positive OHRQoL ¹⁵15. Sekiguchi A, Kawashiri S-Y, Hayashida H, Nagaura Y, Nobusue K, Nonaka F, et al. Association between high psychological distress and poor oral health-related quality of life (OHQoL) in Japanese community-dwelling people: the Nagasaki Islands Study. Environ Health Prev Med 2020; 25:82.. Despite assessing the size and composition of social support networks (friends and relatives), this study did not evaluate the qualitative aspects of these networks, such as the ability of the members to provide emotional or financial support. Our study includes a low-income population exposed to social vulnerability that generates major stressful events and reduces access to adaptation strategies. Therefore, our results may have been partly due to members of the social networks provided individuals with little instrumental/financial support. Social support networks also share health behaviors and mechanisms for adapting to stressful events, which should help decrease stress levels and improve OHRQoL. However, the coping strategies adopted by the participants are unknown and may not be beneficial in the long term. Based on the synergistic effect observed between the variables psychological stress and discrimination, the results confirm previous findings indicating an association between the variables ¹⁷17. Wong CF, Schrager SM, Holloway IW, Meyer IH, Kipke MD. Minority stress experiences and psychological well-being: the impact of support from and connection to social networks within the Los Angeles House and Ball communities. Prev Sci 2014; 15:44-55.^,2020. Bastos JL, Celeste RK, Silva DAS, Priest N, Paradies YC. Assessing mediators between discrimination, health behaviours and physical health outcomes: a representative cross-sectional study. Soc Psychiatry Psychiatr Epidemiol 2015; 50:1731-42.^,4646. Paradies Y, Ben J, Denson N, Elias A, Priest N, Pieterse A, et al. Racism as a determinant of health: a systematic review and meta-analysis. PLoS One 2015; 10:e0138511.. Discrimination causes stress and its main effects are related to psychological well-being ²⁰20. Bastos JL, Celeste RK, Silva DAS, Priest N, Paradies YC. Assessing mediators between discrimination, health behaviours and physical health outcomes: a representative cross-sectional study. Soc Psychiatry Psychiatr Epidemiol 2015; 50:1731-42.^,2121. Pascoe EA, Smart Richman L. Perceived discrimination and health: a meta-analytic review. Psychol Bull 2009; 135:531-54.^,4646. Paradies Y, Ben J, Denson N, Elias A, Priest N, Pieterse A, et al. Racism as a determinant of health: a systematic review and meta-analysis. PLoS One 2015; 10:e0138511.. Previous studies have also found a higher prevalence of stress among Black individuals and indicated that stress mediates the relationship between discrimination and mental health ²⁰20. Bastos JL, Celeste RK, Silva DAS, Priest N, Paradies YC. Assessing mediators between discrimination, health behaviours and physical health outcomes: a representative cross-sectional study. Soc Psychiatry Psychiatr Epidemiol 2015; 50:1731-42.^,4747. Sternthal MJ, Slopen N, Williams DR. Racial disparities in health: how much does stress really matter? Du Bois Rev 2011; 8:95-113.. However, our study shows that the effects of stress and discrimination may be interdependent and that the effect of stress, in the absence of a discriminatory experience, may be insufficient to impact quality of life.

In the current sample, extensive social support networks also did not modify the association between discrimination and OIDP. Social participation may provide individuals with emotional support and decrease their stress levels, which might explain why it has been associated with better mental health indicators ¹⁷17. Wong CF, Schrager SM, Holloway IW, Meyer IH, Kipke MD. Minority stress experiences and psychological well-being: the impact of support from and connection to social networks within the Los Angeles House and Ball communities. Prev Sci 2014; 15:44-55.. Although emotional support seems relevant, economic support may be more important for maintaining good oral health, and it is scarce in a population that receives social benefits. Another possible explanation is that people who experience discrimination seek support from other sources.

One of the limitations of this study is that, as a cross-sectional analysis, we could not determine a temporal relationship between the factors. However, this does not exclude the possibility that worse oral disorders are a source of stressors and can lead to lower social participation ⁴⁸48. Cooray U, Tsakos G, Heilmann A, Watt RG, Takeuchi K, Kondo K, et al. Impact of teeth on social participation: modified treatment policy approach. J Dent Res 2023; 102:887-94.. Furthermore, our findings show the importance of including the qualitative aspects of social support networks into analyses, in addition to their sizes. Another limitation is the lack of internal validity of the discrimination scale for this specific group ⁴⁹49. Bastos JL, Harnois CE. Does the Everyday Discrimination Scale generate meaningful cross-group estimates? A psychometric evaluation. Soc Sci Med 2020; 265:113321.. For example, there are concerns about the face validity of some items for populations that are out of school, only have temporary jobs, and work in public spaces or at home.

Generally, the results confirm previous findings on the positive association between higher levels of stress and worse OHRQoL, and do not confirm the hypothesis of interaction with social support networks. We also found an interaction between psychological stress and discrimination, which is a new and relevant aspect that can be better explored in future research. Our hypothesis is that individuals interact with the resources available in their context in different ways; therefore, the adaptation mechanisms they use to face daily challenges do not always generate health benefits and may not modify the impact of stress and discrimination on oral health-related quality of life. Future studies are needed to evaluate the relationship between OHRQoL and other social support indicators, focusing on the quantitative and qualitative aspects of social support networks.

Acknowledgments

R. K. Celeste, J. L. Bastos, J. B. Hilgert, and F. N. Hugo have a PQ fellowship from the Brazilian National Research Council (CNPq; n. 303775/2021-1 and 308901/2022-3).

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