Association between early childhood caries and intimate partner violence in 20 low- and middle-income countries: 2007-2017

Background: To determine the relationship between country of interpersonal violence (IPV) and the (ECC) Method: This was an ecological study using extracted IPV (physical, sexual and emotional) and ECC data for 3-5-year-olds in 20 low- and middle-income countries for the period 2007-2017. Linear regression analysis was used to assess the relationship between the percentage of 3-5-year-old children with ECC (outcome variable) and the four IPV indicators (physical, sexual, emotional and a combination of the three). The model was adjusted for the country’s Gross National Income GNI. Partial eta squared (as measure of effect size), regression coefficients, confidence intervals and p values were calculated. Results: The strongest association was between ECC prevalence and exposure to physical violence (partial eta squared= 0.01), followed by exposure to sexual violence (partial eta squared= 0.005), and exposure to all types of IPV combined (partial eta squared= 0.001). Exposure to emotional violence had the weakest association with ECC (partial eta squared < 0.0001). For 1% higher percentage of women reporting exposure to physical violence and percentage of women reporting all types of IPV combined, there was a 0.18% higher prevalence of ECC. For 1% higher prevalence of sexual violence, there was 0.22% higher ECC prevalence. For 1% higher prevalence of emotional violence, there was 0.04% higher ECC prevalence. Conclusions: Countries with high prevalence of IPV will likely also have high prevalence of ECC. This needs further studies.


Background
Intimate partner physical, emotional and sexual violence (IPV) is a recognized threat to the health and rights of women globally [1,2]. Global estimates indicated that about 30% of women have a history of IPV with this being highest in central (65.6%) and western (41.8%) sub-Saharan Africa, and South Asia (41.7%) [3]. It is defined as the abuse that takes place between a couple who are either married or living together and may or may not have a child [4]. IPV not only has impact on maternal health and welfare [5], it also has a negative impact on the nutritional status of children of mothers affected by IPV who are more likely to be stunted [6][7][8][9][10][11][12]. This may be due to the negative impact on the mental health of affected women [13] with implications for poor nutritional care [14][15][16] and increased risk for stunting [6-8, 9, 10, 12]; and medical care access problems for children [12,[17][18][19].
Though several studies have established the negative association between maternal mental health and increased risk for ECC [20][21][22][23][24], there is very little known about the association between IPV and ECC. Lorber et al [25] studied children's exposure to domestic violence and the risk for ECC, and found no significant relationship between IPV and ECC though a positive trend was observed.
However, in households where women were aggressive towards men, the risk for ECC was higher due to high exposure to cariogenic diets [26].
The social cognitive theory may explain the relationship between IPV and ECC. The theory recognizes that an individual's behavior, cognition, and environment reciprocally and dynamically influence one another [27]. Key social environmental and personal factors play roles in determining an individual's engagement in health promoting and disease preventing behaviors [28]. Self-efficacy is a central cognitive construct in the social cognitive theory that may predict and explain health behaviors and outcomes [29][30][31]. Thus, a person's belief or confidence in their ability to perform certain actions influences the decisions to perform these actions [32], including tooth brushing [33], which is a significant risk factor for poor oral hygiene and ECC [34]. IPV undermines self-efficacy of affected individuals [35,36] who are mostly women [37] serving as care-takers for children [38]. IPV can therefore compromise the ability of women to care for children who are completely dependent on them for daily oral hygiene and accessing professional oral health care services.
The aim of this study was to determine the relationship between country level prevalence of IPV and the prevalence of ECC in children aged 3-5-year-olds in countries where data on IPV and ECC are available. We conducted country-specific analysis in view of the evidence suggesting differences in the relationship between IPV and ECC [39].

Methods
This ecological study was based on IPV data extracted from the domestic violence module of the Demographic Health Survey, a nationally representative household survey that collects information on population-based indicators of health and nutrition in low-and middle-income countries (LMICs).
The module includes questions on types and experiences of violence (physical, sexual and emotional) mostly perpetrated by the current or most recent husband/ partner [40]. The present study also used data on ECC collected by El Tantawi et al [42]. Data for both IPV and ECC were available in only 20 LMICs between 2007 and 2017.
Early childhood caries: Early childhood caries is identified in children < 72 months of age with one or more decayed (cavitated and non-cavitated), missing due to decay or filled primary tooth surfaces Confounders: Income level was reported to be associated with ECC [41] and IPV [3]. We adjusted for country income level based on the 2015 Gross National Income (GNI) per capita calculated using the World Bank Atlas method [44] since it was the latest available for the study period.

Statistical analysis:
The datasets (ECC and IPV indicators) were matched by country. Analysis was restricted to only women selected and successfully interviewed in the DHS domestic module and those who were formerly or currently in union or living with a man at the time of survey. Statistics, including means and standard deviations (SD), were calculated for IPV indicators, ECC and GNI. Linear regression analysis was used to assess the relationship between the percentage of 3-5-year-old children with ECC (outcome variable) and each IPV indicator adjusted for GNI. Regression coefficients, 95% confidence intervals (CIs), p values and partial eta squared (as measure of effect size) were calculated using SPSS version 22.0 (IBM Corp., Armonk, N.Y., USA). Significance level was set at 5%.

Results
Data on ECC in 3-5-year-olds and IPV were available for 20 LMICS. These 20 countries included six low-income countries (30%), 10 lower-middle-income countries (50%) and four upper-middle-income countries (20%). In view of the small number of countries with available data, analysis was conducted for all 20 countries collectively rather categorized by income level. Table 1

Discussion
This was the first study attempting to study the association between IPV and ECC using national data available from multiple countries around the world. This data suggest that in countries with higher proportion of women facing physical, sexual and emotional IPV, the prevalence of ECC is also higher.
This relationship was not statistically significant likely due to the relatively few number of countries with available information from the Demographic Health Survey. In addition, the effect size observed is small though this not unexpected in view of the multifactorial nature of ECC and because IPV may be partly explained by the other major social determinant of health like education and income (for which we controlled in our analysis). The study finding however highlights an area for future research as there are indications that the global incidence of IPV has been on the increase [45]. The pathway for this association also needs to be further studied. This includes studying the possible link between IPV and culture, association between IPV and the presence/absence of national laws that protect women and their rights.
The study provides new information to strengthen existing evidence on how social context is associated with disease risks. Globally, the prevalence of ECC is high -it is the 10th most prevalent childhood illness [46]. Most of the efforts to address this problem have largely been limited to interventions aiming at altering biological and behavioral risk factors. Little attention has been paid to addressing the social determinants of health, which can impact the behavioral and biological risks.
Highlighting how IPV impacts negatively on the oral health of pre-school children has two implications: the percentage of children with ECC in LMICs may be associated with care-givers' risk of exposure to IPV. Identification of caregivers experiencing IPV may help with identifying child at risk for ECC at a young age. The first implication also reiterates the importance of integrated maternal and child health care as a cost-effective mechanism to manage diseases using the common risk approach [47]. There is currently very little evidence on approaches that promote the integration of maternal and child general healthcare with their -and especially the child's-oral health. As evidence emerges, it will be important to develop programs addressing maternal IPV and ECC in pre-school children as part of a general health screening process, especially in countries where the prevalence of IPV is high.
The second implication of the finding from this study is the challenge with planning macro-level interventions and using micro-level measures to assess success. Pending further confirmation from future studies, the association between IPV and ECC shown in this study may indicate the possibility of using ECC prevalence to monitor the success of country-level programs addressing IPV. However, there are very few countries that conduct regular national oral health surveys; and fewer that collect oral health data in pre-school children. Our findings highlight the importance of national ECC surveys so that this data can be used as an indirect, although may be less sensitive measure, of the impact of interventions to control IPV. Existing studies and reviews of the IPV and oral health literature reveal that the link between IPV and ECC is quite plausible [48]. Integrating early childhood promotion and ECC prevention messaging into women's shelters may be a first step to reduce the risk for caries and offer women practical methods to care for their children's oral health.
One of the strengths of the present study is the use of population-level data derived from the Demographic Health Survey thus ensuring data quality [49]. We used the data from 20 LMICs to provide insight to a phenomenon that if further explored, may shape policy and practice around ECC management [50]. Our study is however limited by the low number of included countries thereby challenging the generalizability of findings. The low sample size was addressed by using partial eta squared, a measure of effect size, to compare the association of ECC with various forms of IPV and to decide on the importance of each variable, rather than using the p values to determine the significance of the associations. Ensuring the availability of IPV data in other countries with different income levels may help develop a better understanding of the nature of the association between ECC and IPV.
Another limitation is that IPV data is based on self-reporting with the possibility of under-reporting due to social desirability bias [51]. However, this is the standard method used to obtain IPV statistics [52].
In addition, the study is ecological with potential for ecological fallacies [53, 54]; and its crosssectional design has limited use in establishing a cause-effect relationship between ECC and IPV. We also only extracted data on IPV and women though there are evidence suggestive that both males and females may be victims of IPV [55, 56]; and IPV affecting men may be associated with the risk of ECC [26].

Conclusions
Despite these limitations, the study provides new insight into the possible association between ECC and IPV: physical, sexual and emotional violence were associated with ECC prevalence though the associations were not significant. Women's exposure to physical and sexual violence had greater association with the prevalence of ECC than other types of IPV.