Impact of Cash Transfers on the Use of Oral Health Services and Oral Health Outcomes: A Systematic Review.

Objective: The objective of the present study was to summarize the evidence available on the impact of cash transfers on the use of oral health services and oral health outcomes. Materials and
Methods: 9 databases were searched for studies on cash transfers and oral health: PubMed, Embase, The Cochrane Library, CINAHL, EconLit, Dentistry and Oral Sciences Source, Scopus, Web of Science, and LILACS. We conducted a systematic review of studies that evaluated the impact of cash transfers on the use of oral health services and other oral health outcomes.
Results: Three studies with more than 13,000 participants conducted in Brazil and Argentina were included. One study from Brazil found that participants in the Bolsa Familia Program (BFP) were more likely not to use oral health services (aPR: 6.18; 95% CI: 3.07-12.45; P < 0.001) and had a higher probability of presenting dental caries (aPR: 2.00; 95% CI: 1.47-2.69) and severe caries (aRR: 1.53; 95% CI: 1.18-2.00). Another study conducted in Brazil found that the BFP was associated with fewer dental caries among those enrolled in the first 2 years of the BFP as well as after six years. On the other hand, the Argentina study found that the Universal Child Allowance program did not have a statistically significant average treatment effect (ATE = -0.05; P > 0.05) on the use of dental health services.
Conclusion: There is a lack of evidence about the impact of CT on the use of oral health services and oral health outcomes. The evidence suggests that cash transfers might not have a positive impact on the use of oral health services. The results regarding the impact of receiving cash transfers on dental caries are contradictory. However, more evidence is needed to draw stronger conclusions for policy taking. Registration: The protocol was registered in PROSPERO (CRD42021268234). Copyright:

INTRODUCTION

Oral diseases are the most prevalent diseases in the world, affecting 3500 million people worldwide, mainly in developing countries.[12] The prevalence of oral diseases is unequal according to the level of country development. Thus, while developing countries, which have a higher proportion of the population living in poverty and extreme poverty, show a high prevalence and a tendency to increase these diseases, developed countries show the opposite trend.[1]

Inequalities in oral health are governed by determinants at the individual, health system, and contextual levels. In developing countries, the inability to afford treatment and/or access to dental services, due to lack of insurance or unequal distribution of health services at the territorial level impact oral health inequalities.[3] Considering this, the governments of several countries have implemented cash transfer (CT) programs aimed at reducing inequalities in different areas such as health, including oral health, and education, alleviating current poverty and breaking its intergenerational transmission.[45]

Worldwide, there is evidence of the positive impact of CT on improving health and living conditions.[4] In Nicaragua, the number of people below the poverty line was reduced by 5 to 7 percentage points after implementing a conditional CT program, while in Colombia, a similar program reduced the poverty gap by almost 7 percentage points.[6] Similarly, some studies that systematize this evidence have concluded that CTs could have a positive impact on mental health outcomes, the use of general health services, poverty, education, nutrition, and sexual risk behaviors, among others, in different population groups. However, to date, no study has systematized the evidence of the impact of CT on the use of oral health services and oral health.[7891011]

Therefore, the objective of the present study was to summarize the evidence available on the impact of CTs on the use of oral health services and oral health outcomes by performing a systematic review of the published scientific literature on this subject.

MATERIALS AND METHODS

The systematic review protocol was registered in the Prospective International Registry of Systematic Reviews (PROSPERO) under identification number CRD42021268234. This systematic review with meta-analysis was reported following the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA 2020) guidelines[12] and the Synthesis Without Meta-analysis (SWiM) guideline.[13]

SEARCH STRATEGY AND DATA SOURCES

We searched for all potentially relevant studies reporting the relationship between CTs and the use of oral health services and oral health outcomes published from the date of creation of the bibliographic databases used until July 18, 2021. Nine electronic bibliographic databases were searched: PubMed, Embase, The Cochrane Library, CINAHL, EconLit, Dentistry and Oral Sciences Source, Scopus, Web of Science, and LILACS. The search strategy was performed by an experienced medical research librarian (DC) and validated by the research team. An EPOC (Cochrane Effective Practice and Organisation of Care Group)[14] methodology filter was used to limit retrieval to appropriate study designs (https://epoc.cochrane.org/). Full details of the search strategies are shown in Supplementary Table 1. We hand searched the reference lists of all records of included studies.

The records found in the electronic search were imported into the EndNote X9 reference management software, and all duplicate records were removed following the procedures described by Bramer et al.[15]

IDENTIFICATION AND SELECTION OF STUDIES

In line with EPOC criteria, the following studies were included: (a) randomized controlled trials or cluster-randomized controlled trials, non-randomized controlled trials, controlled before-after studies, interrupted time-series studies, modeling studies and comparative observational studies if they provided information regarding the relationship between CTs and oral health service utilization patterns and oral health outcomes; (b) if there were two or more studies with equal populations, the study with the larger sample size was selected. We excluded articles: (a) in which the allocation of the CT could not be determined; (b) that were not published in English, Spanish, or Portuguese; and (c) included review articles, case reports, book chapters, editorials, and letters.

Two review authors (GBM and FBL) independently assessed the titles and abstracts of all the articles identified in the search and met the inclusion criteria using the Rayyan web application.[16] Discrepancies in decisions were resolved by consensus or discussion with a third author (AHV). All the records included proceeded to the full-text evaluation phase by the same two authors (GBM and FBL). Any disagreement about the inclusion or exclusion of an article was resolved with a third author (AHV).

VARIABLES AND MEASURES

The variable of interest was direct CTs to households or their inhabitants, which can be conditional or unconditional on behavior, action, or health goals.

The following main outcomes allowing comparisons between intervention and control groups were considered: (a) changes in the use of oral health services: changes in utilization patterns of oral health facilities or services and/or equivalent information collected directly through rigorous survey techniques; and (b) changes in oral health outcomes: incidence of morbidity and mortality (when measured or available) (e.g. dental caries, periodontal diseases, oral hygiene, edentulism, oral infections, among others). Secondary outcomes include the changes in inequalities of access: increased access for disadvantaged groups or a reduction in gaps in coverage which could also be an important outcome measure. This required a preliminary analysis and categorization of the population of interest along a socio-economic scale (i.e., wealth index).

DATA COLLECTION

Data were independently extracted by two authors (DA and RVF) using a data extraction form previously piloted in Microsoft Excel, and any discrepancies were resolved by consensus or discussion with a third author (AHV). Data were extracted including: first author, year of publication, country of study, language of publication, study design, setting, study population, sample size, and crude or adjusted odds ratios (OR) or risk ratios (RR), with their corresponding 95% confidence interval (CI). A third author (AHV) checked the accuracy of the extracted data.

ANALYSIS AND INTERPRETATION OF INFORMATION

Owing to differences in reported quantitative data and the small number of studies, meta-analysis was not possible,[17] and the findings are presented in a narrative form. The general data of the publications and the specific data related to the objective of this study were collected in summary tables in the Microsoft Excel program. The data were examined with descriptive analysis; for quantitative variables measures of central tendency were reported as mean, standard deviation, minimum and maximum values; and for qualitative variables frequencies were reported.

EVALUATION OF THE QUALITY OF THE STUDIES INCLUDED

The quality of the studies included was independently assessed by two authors (GBM and FBL) and consensus was reached between the two authors in case of disagreement. The Joanna Briggs Institute (JBI) Critical Appraisal Checklist for Analytical Cross Sectional Studies and Quasi-Experimental Studies was used to determine the quality of the studies.[18]

RESULTS

CHARACTERISTICS OF THE STUDIES INCLUDED

A total of 2837 studies were included for evaluation by titles and abstracts, of which 6 were eligible for full-text evaluation. Only 3 studies met the criteria for inclusion in the systematic review[5, [Figure 1]. Three studies were excluded by irrelevant intervention.[212223] The studies included were published in 2013, 2018 and 2020. Two were conducted in Brazil[1920] and one in Argentina.[5] Two studies were cross-sectional[1920] and the other had a quasi-experimental design,[5] and all were published in English.

Figure 1

PRISMA 2020 Flow diagram of study selection

Adopted from: Page MJ, McKenzie JE, Bossuyt PM, Boutron I, Hoffmann TC, Mulrow CD, et al. The PRISMA 2020 statement: an updated guideline for reporting systematic reviews. BMJ 2021;372:n71. doi: 10.1136/bmj.n71

The study by Corrêa et al.[19] conducted in 2010 included children aged 8 to 12 years enrolled in schools in an urban area of the city of Pelotas in Brazil, while the study by Calvasina et al. was performed in children aged 5 years registered in the national unified social system registry (CadÚnico).[20] The third study by Walsh et al.[5] was conducted at the population level from 2012–2017 in children from urban areas of Argentina aged 3 to 17 years. Table 1 provides further information on the characteristics of the studies included.

Table 1

Characteristics of the studies included

Author (year)	Study type	Country	Data collection period	Sample size (n)	Intervention group				Control group
					Age range (years)	Sex n (%)	Sample size (n)	Type of Cash Transfer	Age range (years)	Sex n (%)	Sample size (n)	Type of control
Corrêa et al. (2013)	Cross-sectional	Brazil	2010	1107	8 to 12	Male (122, 46.4%) Female (141, 53.6%)	263	Conditional, BFP	8 to 12	Male (407, 48.2%) Female (437, 51.8%)	844	Without access to BFP
Walsh et al. (2020)	Quasi-experimental	Argentina	2012-2017	12507	3 to 17	Male (3706, 51.1%) Female (3548, 48.9%)	7254	Conditional, UCAP	3 to 17	Male (50.1%) Female (49.9%)	5253	Without access to UCAP
Calvasina et al. (2018)	Cross-sectional	Brazil	2016	230	5	NR	167	Conditional, BFP	5	NR	63	Without access to BFP

BFP: The Bolsa Familia Program, UCAP: The Universal Child Allowance Program.

TYPES OF CASH TRANSFERS EVALUATED

As the intervention of interest, the studies by Corrêa et al.[19] and Calvasina et al.[20] evaluated the Bolsa Familia program (BFP),[24] which includes CTs conditional to the achievement of indicators of access to health, education and social assistance, given to households living in poverty and extreme poverty. The study by Walsh et al.[5] evaluated the impact of the Universal Child Allowance program (UCAP) implemented by the Argentine government,[25] which provides the same type of CTs preferably to mothers of children who meet certain criteria including: unemployment of both parents, and who demonstrate compliance with the educational and health conditions established by the program [Table 1].

RESULTS OF THE USE OF ORAL HEALTH SERVICES

The study by Corrêa et al.[19] evaluated the use of oral health services in recipients and non-recipients of the BFP. The crude (cPR) and adjusted prevalence ratios (aPR) were reported as a measure of association, taking into account the non-use of dental health services at some time in life as an outcome. It was determined that those who received CTs from the BFP were more likely not to use oral health services (aPR: 6.18; 95% confidence interval [CI]: 3.07–12.45; P < 0.001) compared to those who did not receive CTs from the program and studied in private schools. As for the study from Argentina,[5] it was determined that the UCAP did not have a statistically significant average treatment effect (ATE = -0.05; P > 0.05) on the use of dental health services [Table 2].

Table 2

Impact of cash transfers on the use of dental services and other oral health outcomes

Author (year)	Outcomes
	Primary outcome		Other oral health outcomes
	Frequency of use of dental services		Presence of dental caries		Presence of severe dental caries
	Measure of association	Adjustments	Measure of association	Adjustments	Measure of association	Adjustments
Corrêa et al. (2013)	For not using dental services: PR: 9.30 (95% CI: 4.97-17.44) and aPR: 6.18 (95% CI: 3.07-12.45)	Maternal schooling, family structure, sex, age, presence of plaque, fear of dentist.	For the prevalence of dental caries: cPR: 2.29 (95% CI: 1.70-3.08) and aPR: 2.00 (95% CI: 1.47-2.69)	Maternal schooling, family structure, sex, age, presence of plaque, fear of dentist.	For the presence of severe dental caries: RR: 1.95; 95% CI: 1.55-2.47 and aRR: 1.53; 95% CI: 1.18-2.00	Maternal schooling, family structure, sex, age, presence of plaque, fear of dentist.
Walsh et al. (2020)	Average treatment effect (ATE): -0.05 (not significant)	Sex, age, education of mother or guardian, age of mother or guardian, employment of head of household,	Not evaluated	NA	Not evaluated	NA
		region of residence, survey year, lives with mother, lives in villa, slum, or settlement,
		overcrowding in rooms, poor housing material, extended family in home, household income quintile.
Calvasina et al. (2018)	Not evaluated	DNA	Odds ratio for years of BFP enrollment by model (M) Not recipient: M1: 1.00; M2: 1.00; M3: 1.00; M4: 1.00	M1: crude model; M2: access to fluoride water, frequency of teeth brushing, childrens’ sex, oral hygiene instruction, marital status, education, and per capita income:	Not evaluated	NA
			0-2 years: M1: 0.37*; M2: 0.15*; M3: 0.13*; M4: 0.94	M3: access to fluoride water, frequency of teeth brushing, children’ sex, oral hygiene instruction, marital status, education, per capita income, reasons for dental visit;
			2-5 years: M1: 0.72; M2: 0.49; M3: 0.53; M4: 1.92	M4: access to fluoride water, frequency of teeth brushing, children’ sex, oral hygiene instruction, marital status, education, reasons for dental visit, interaction between years of BFP enrollment with per capita income.
			More than 6 years: M1: 0.48; M2: 0.27*; M3: 0.29*; M4: 2.14

PR: prevalence ratio; cPR: crude prevalence ratio; aPR: adjusted prevalence ratio; RR: risk rate; aRR: adjusted rate ratio; 95% CI: 95% confidence interval; NA: not apply.

BFP: The Bolsa Família Program,

* p<0.05

OTHER ORAL HEALTH OUTCOMES ASSESSED

The study by Corrêa et al.[19] reported the association between receiving or not receiving CTs from the BFP and the presence and severity of dental caries. Those who received CTs from the program had a higher probability of presenting dental caries (PR: 2.00; 95% CI: 1.47–2.69; P < 0.001) compared to those not receiving CTs and studying in private schools. Likewise, those who received CTs from the BFP had a higher risk of presenting severe dental caries than those not receiving CTs and studying in private schools (adjusted rate ratio [aRR]: 1.53; 95% CI: 1.18–2.00; P = 0.007) [Table 2].

Likewise, using four logistic regression models the study by Calvasina et al.[20] reported the association between the number of years that a family was a beneficiary of the BFP compared to not receiving CTs, and the presence of dental caries in 5-year-old children.[20] Model 3 showed that having between 0–2 years as a beneficiary of the program was associated with a lower probability of dental caries (adjusted odds ratio [aOR]: 0.13; 95% CI: 0.05–0.35; P < 0.05), as was having more than 6 years as a beneficiary (aOR: 0.29; 0.10–0.82) compared to not being a beneficiary. However, Model 4, which included an interaction between years as a beneficiary and family per capita income, showed no association between the years as a beneficiary of the program and the presence of dental caries [Table 2].

Except for the item not applicable to the complete follow-up of participants in the Walsh et al. study,[5] all the studies obtained the maximum number of assertive responses regarding their methodological quality [Table 3].

Table 3

Quality of the studies included

Author (year)	JBI / Quasi-experimental studies	Is it clear in the study what is the ‘cause’ and what is the ‘effect’?	Were the participants included in any comparisons similar?	Were the participants included in any comparisons receiving similar treatment/care, other than the exposure or intervention of interest?	Was there a control group?	Were there multiple measurements of the outcome both pre and post the intervention/exposure?	Was follow up complete and if not, were differences between groups in terms of their follow up adequately described and analyzed?	Were the outcomes of participants included in any comparisons measured in the same way?	Were outcomes measured in a reliable way?	Was appropriate statistical analysis used?
Walsh et al, 2020	8/9	Yes	Yes	Yes	Yes	Yes	Not Applicable	Yes	Yes	Yes
Author (year)	JBI / Analytical cross sectorial studies	Were the criteria for inclusion in the sample clearly defined?	Were the study subjects and the setting described in detail?	Was the exposure measured in a valid and reliable way?	Were objective, standard criteria used for measurement of the condition?	Were confounding factors identified?	Were strategies to deal with confounding factors stated?	Were the outcomes measured in a valid and reliable way?	Was appropriate statistical analysis used?	-
Corrêa et al, 2013	8/8	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	-
Calvasina et al, (2018)	7/8	Yes	Yes	Yes	No	Yes	Yes	Yes	Yes	-

DISCUSSION

This systematic review sought to determine the impact of CTs on the use of oral health services and oral health outcomes. A total of three studies met the inclusion criteria and were published in English in 2013, 2018, and 2020. Two studies had a cross-sectional design and were conducted in children aged 8 to 12 years enrolled in schools in an urban area of Brazil and in 5-year-old children registered in the CadÚnico program, and the third had a quasi-experimental design and was conducted in children aged 3 to 17 years from urban residential areas in Argentina. The CTs evaluated were from the government BFP in Brazil[1920] and the UCAP in Argentina.[5] An important finding of this systematic review is the scarcity of studies published in the databases consulted that evaluate the impact of these types of measures on oral health. However, this may be because evaluations of these types of programs are usually reported through governmental reports not published in scientific journals. According to the results of the studies included, two studies found no positive effect of CTs on the use of oral health services[519] or on the presence or severity of caries,[19] while the study by Calvasina et al.[20] reported that 5-year-old children receiving CT were less likely to present dental caries, although this association was lost after adjusting the model for the interaction between the number of years as a beneficiary of the program and the level of per capita income.

Regarding the use of oral health services, those receiving CT were more likely not to use oral health services in Brazil, whereas, in Argentina, the receipt of CTs did not have a statistically significant effect on the use of oral health services. This finding is consistent with a systematic review by Pega et al. who conducted a search for potential articles until May 2017.[10] In this systematic review, it was noted that unconditional CT would not have an impact on the use of health services in general used by children and adults in low- and middle-income countries.[10] This implies that the use of CT alone may not be able to reduce health inequalities particularly in low- and middle-income countries, in which other factors such as: limited number of health services, geographic inaccessibility to these services, culture and beliefs, and poor health systems may need to be addressed in order to overcome barriers to health access.[2627] In contrast, a systematic review of studies in sub-Saharan Africa showed that conditional CT could have a positive effect on children’s access to health services and nutrition.[9] The latter suggests that in certain populations there is a need to condition the provision of CT to oral health services in order to function properly; for example, in those with a majority of households in which the members do not have a full understanding of the benefits of access to health services.[28]

Another relevant outcome was the presence of caries. The study by Corrêa et al.[19] reported that families that received CTs from the BFP were more likely to have dental caries and severe dental caries, while the study by Calvasina et al.[20] showed that 5-year-old children who received CTs from this program were less likely to have dental caries. However, in the latter study only point estimates with statistical significance were observed in the models that considered a period of enrollment in the BFP of 0 to 2 years and more than 6 years and were adjusted for sociodemographic and economic variables specific to a specific province of Brazil, which may compromise the external validity of the results. Moreover, the association was lost after adjusting the model for the interaction between the number of years as a beneficiary of the program and the level of per capita income. Thus, the findings are contradictory and could be explained by the setting in which they were carried out and the characteristics of the population included. On the other hand, it should be considered that some social inequalities related to the occurrence of dental caries, such as inadequate nutrition, lack of access to water and sanitation, low educational level, and limited access to oral health services, which may or may not be reversed by CT, were not measured as adjustment variables in these studies.[29] Thus, better access to health services and CTs should consider the characteristics of the population and their socio-economic conditions and the factors that could influence the appearance of dental problems in order to develop strategies for the prevention and treatment of dental caries, especially in regions in which health systems are limited.

Only three studies evaluated the impact of CT on the use of oral health services and oral health outcomes (one from Argentina and two from Brazil).[519,20] The paucity of information of the impact of CTs on oral health in various regions of the world, especially in low- and middle-income countries, highlights the need for more studies, especially considering the greater inequalities in the use of health services compared to high-income countries.[30] This lack of information prevents decision-makers from identifying the benefits of these programs in low-income populations in order to reduce the burden of disease and the health costs of preventable dental problems.

Among the main limitations of this systematic review, the search for gray literature was not taken into account, and there may be reports of impact evaluations of programs published on governmental web pages. Additionally, the data were obtained from studies using different designs, with only one study performing an impact analysis to estimate the effects of CT on oral health. Also, the studies included may have problems with external validity. Nonetheless, this systematic review followed a rigorous process of elaboration, and the selection of evidence and data extraction were undertaken by independent peers and complied with the specific items for systematic reviews of the PRISMA checklist, and complemented by the SWiM guide. Similarly, a systematic search was conducted in the main bibliographic databases used in health, some of which are specific to oral health-related topics, in order to cover the maximum number of studies with potential for inclusion. Finally, our study reports updated evidence of the impact of CT on the use of oral health services and oral health outcomes, with the aim of providing relevant information on the impact of these CT programs on health systems.

In conclusion, the scarce information available of the impact of CT on the use of oral health services and oral health outcomes was obtained from Latin American countries, in which CTs have shown to have no positive impact on the use of oral health services and contradictory results regarding the presence and severity of dental caries. This scarcity of information prevents health systems and policy makers from issuing recommendations on CT, making greater scientific production on the impact of these programs necessary in order to estimate the benefits of CTs on oral health. Considering that oral diseases represent one of the greatest burdens of disease worldwide and have a great social and economic impact mainly in developing countries, the CT programs of these countries should be redesigned and duly monitored to achieve oral health indicators and established oral health outcomes.

ACKNOWLEDGEMENT

The authors are grateful to Donna Pringle for reviewing the language and style.

FINANCIAL SUPPORT AND SPONSORSHIP

The authors received no specific funding for this work.

CONFLICTS OF INTEREST

There are no conflicts of interest.

AUTHORSHIP CONTRIBUTIONS

AHV and DA conceived the study. All authors contributed to the study design. AHV and DA planned, supervised, and validated the work. DC executed the bibliographic search. DA and RVF extracted the data from the studies. BH, AHV, DA, and RVF analyzed the results and wrote the manuscript. All authors contributed to the preparation of the tables and figures. All authors critically reviewed and approved the final manuscript.

ETHICAL POLICY AND INSTITUTIONAL REVIEW BOARD STATEMENT

Not applicable.

PATIENT DECLARATION OF CONSENT

Not applicable.

DATA AVAILABILITY STATEMENT

Not applicable.

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