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The United States (U.S.) and Canada experienced sharp increases in the numbers of people reporting inadequate food beginning in the 1980's likely related to changes in the work-force, the nature of work and the compensation workers received.1 The number of food banks also increased during that time period to meet the food needs of the population.1 The term "food insecurity," defined as "limited or uncertain availability of nutritionally adequate and safe foods, or limited or uncertain ability to acquire acceptable foods in socially acceptable ways,"2 was first introduced in 1990 and remains a significant social and public health concern today.3 Although food insecurity has been an issue for generations of people, there has been an increase in food insecurity in the U.S. beginning with the Great Recession of 2007 - 2009.4 The concept of a food desert (an area of 500 people, or a census tract where 1/3 of the residents must travel more than one mile to a supermarket/large grocery store; or a rural area where the residents must travel more than ten miles to a supermarket/large grocery store) was introduced during this period and continues to be used to describe many geographic areas in the U.S.8 Difficulty in food access often involves individual's settling for the foods that are available closer to one's home. Such options are often highly refined, calorie-laden, low-nutrient, less expensive foods with a long shelf-life. Lack of proper nutrition impacts health in many ways and there is the potential for food insecurity to be related not only to poor general health, but also to poor oral health.
One of the proposed mechanisms for the relationship between food insecurity and poor dental health is that a high carbohydrate load, particularly of highly refined carbohydrates, provides an oral environment conducive to the development of biofilms containing cariogenic bacteria.9-10 It has been reported in the literature that children living in households with food insecurity were more likely to have untreated dental caries;11-12 however, it is unknown if such an association exists in adults. In order to study the impact of food insecurity on unmet dental need in the adult population, the Andersen Behavioral Model of Health Services Usage was utilized.13 This instrument provides a conceptual framework for studying vulnerable populations and health disparities. Under the Andersen model, increased service use or need for such use is determined by a number of factors broadly categorized as: immutable predisposing factors, enabling factors, and personal health practices. In this study, healthcare service need for unmet dental care was considered to be influenced by predisposing factors (e.g. sex; age; race or ethnicity), not having enabling factors (e.g. education; social support through marriage or partnership; adequate income; and the interest of the study, food security), and not having healthful personal health practices and/or conditions (e.g. smoking; alcohol use; previous dental visit over a year ago). The purpose of this study was to determine the association between low food security and unmet dental care needs in adults in the U.S.
Methods
This study received institutional ethics acknowledgement and approval as non-human subject research (secondary data analysis of collected, publicly available data).
Study design
An observational, retrospective, cross-sectional design with data obtained from the National Health and Nutrition Examination Survey (NHANES), 2011 and 2012, was used for the study.14
NHANES researchers from the Centers for Disease Control and Prevention (CDC) used stratified, multistage probability sampling designs for the surveys to select participants who were non-institutionalized civilians and lived in the U.S. (including Washington, DC).14 The researchers oversampled smaller subgroups to increase estimate accuracy. Participants responded to interview questions involving demographic information and questions regarding health and nutrition. Data for the oral examination were collected in a mobile examination center by calibrated licensed dentists who received extensive and periodic training and re-calibration. Details of the NHANES study methodology for 2011 and 2012 are available on the NHANES website.14
The study population sample was comprised of adults, age 20 years and above, who had no missing data in the areas of household food security, unmet dental care need, sex, race/ethnicity, and age from the NHANES 2011-12 and consisted of 4,845 participants.
Measures studied
Unmet dental care need was the dependent variable. Individuals were considered to have an unmet dental care need if the NHANES dental examiner recommended that the participant be seen by a dentist. Conversely, individuals were considered to have no unmet dental care need if the examiner recommended that the participant continue with regular, routine care.
Food security was the key independent enabling variable. CDC researchers created a household food security variable in the NHANES 2011 and 2012 data sets based upon the U.S. Food Security Survey Module questions of Bickel, et al.15 The 2011-12 survey contained 18 questions related to difficulties in food access, availability and quality for households with children; and 10 questions for households without children.15 Affirmative responses to the food security module questions were tallied and categorized as shown in Table I. Households indicating no affirmative responses, were defined as having "full" food security. Households indicating 1-2 positive responses, were defined as having a "marginal" food security. Households without children under the age of 18 years, indicating 3-5 positive responses, or households with children under the age of 18 with 3-7 positive responses, were defined as having "low" food security. Households in which there were no children under the age of 18 years indicating 6-10 positive responses, or households with children and indicating 8-18 positive responses, were defined as having "very low" food security. If a household had children, but the respondent refused or did not answer the questions concerning the children, the household was classified using the criteria for households without children in the NHANES research. In the data analysis for this study, the categories "low" and "very low" food security were combined (due to small sample sizes) into the category of low food security.
A logistic regression model for the presence of unmet dental need was built incorporating other enabling variables (i.e., factors known to impact access to services), predisposing variables, and personal health practices and/or conditions. Additional enabling variables used in the study were: educational level (less than high school; high school graduate; some college/technical school; college/technical school graduate or above), marital status (married; widowed/divorced/separated/never married); medical insurance (yes; no); family federal poverty ratio (0 to less than 1.25; 1.25 to less than 2.00; 2.00 to less than 4.00; 4.00 and above). The family federal poverty ratios listed here have been used in previous research,16 however, the federal government does not have definitions related to low income, middle income, upper income, etc.
The predisposing variables used in this study included: sex (male; female), race/ ethnicity (non-Hispanic White; non-Hispanic Black; Mexican-American or other), and age (20 to under 35; 35 to under 50; 50 to under 65; 65 and above). Personal health practices and/or conditions used in the study were smoking status (current smokers; former smokers; never smokers), body mass index (less than 25; 25 to less than 30; 30 and above), alcohol use (none; moderate [1-2 drinks per day]; heavy [more than 2 drinks per day]), and dental visits (within 6 months; within 1 to 2 years; more than 2 years).
Statistical analyses
Chi square tests were used to examine the unadjusted association between dental care need, food security and the other independent variables. Logistic regression was used to examine the association between food security and dental care need with two different models: an unadjusted model and a model adjusted for predisposing factors, enabling factors, and personal health practices. All analyses included sampling weights to account for the complex NHANES survey design and were conducted using the Statistical Analysis System Software (SAS® version 9.3, SAS Institute, Inc.; Cary, NC, USA).
Results
Descriptive sample characteristics are presented in Table II. Unmet dental need was identified in 47% of the adults in the sample and low food security was found in 16% of the sample population. The majority of the sample was non-Hispanic White (66.8%), married (61.6%) and insured (79.9%).
Sample results for unmet dental need are presented in Table III. The association of unmet dental care need for participants with low food security vs. those with full food security (70% vs. 41%) was significant (p<.0001). There were also significant associations between unmet dental care need and the predisposing factors, enabling factors, and personal health practices/conditions. Unmet dental care need was reported by a higher percentage of non-Hispanic Black as compared to non-Hispanic White (66.3% vs. 40.2%), and adults living below the 1.25 times the family federal poverty level compared to adults living at or above 4.00 times the family federal poverty level (64.1% vs. 31.3%).
In the adjusted analysis, adults with low food security were more likely to report unmet dental care need as compared to adults with full food security (Adjusted Odds Ratio (AOR) = 1.58, 95% CI = 1.18, 2.12; P <.01). Adjusted Odds Ratios and 95% confidence intervals for the other independent variables are presented in Table IV. Interaction analyses of food security with age, race/ethnicity, and federal poverty level supported the significant positive adjusted analysis association.
Discussion
The purpose of this study was to examine the association between food security and unmet dental care need in adults. Adults with low food security were more likely to have unmet dental care need as compared with adults with full food security. These findings are consistent with a Canadian study in which Muirhead et al. found that adults who reported food insecurity had poorer oral health and were more likely to be wearing dentures than adults who had food security.1 Results of this study are also consistent with other studies among children with low or very low food security,11,15 and a study with school lunch programs in Brazil.17
Addressing low food security
Low food security is a consideration in the larger social context of food justice which includes issues such as local food movements, toxin-free foods, public investment/community development to regain supermarkets/large grocery stores, and labor laws, among other issues.15 Efforts are being made to address individual and community needs for safe, healthful, and adequate food sources and have been supported by the U.S. Department of Agriculture (USDA).15 Food deserts have been the primary foci of these efforts. When communities lose or do not have access to supermarkets or large grocery stories, non-traditional food retailers (i.e. gas-marts, pharmacies, dollar stores, small grocery stores) may fill the void; but often those retailers do not stock fresh fruits and vegetables.18 Such markets with limited food choices often stock heavily processed, sugary foods and beverages.19
The USDA supports a variety of healthful feeding programs: the National School Lunch Program fed more than 20 million free lunches per school day to children in 2017;20 and the Women Infants and Children (WIC) program had 7.3 million participants in 2017.21 Additional programs from the USDA include the Supplemental Nutrition Assistance Programs (SNAP), School Breakfast Program, Fresh Fruit and Vegetable Program; Summer Food Service Program, Commodity Supplemental Food Program, Food Distribution Program on Indian Reservations, the Emergency Food Assistance Program, Special Milk Program, Farmers' Market Nutrition Program, and the Senior Farmers' Market Nutrition Program.22 However, many people with low food security do not have access to the programs, are ineligible, or do not know about them. This lack of utility of the available food supplementation programs is a concern for general health; and, as indicated by our study results, is also a concern for unmet dental needs.
Low food security and health needs
This study indicates a link between unmet dental needs and low food security with adults having low food security being 58% more likely to have an unmet dental need (AOR= 1.58, 95%CI=1.18, 2.12; p<.01). Relationships between low food security and other health needs including unmet dental care need, require better understanding. Low food security is experienced differently for household of adults with children.3 Children are found to experience less food insecurity than their mothers in the same household;3 the child's needs are placed before the needs of the parent. Low-nutrient, high-calorie, and highly processed foods are often low-cost and readily available; and food prices strongly influence food purchases.23 Individuals with food insecurity often have diets which are pro-inflammatory, and cariogenic. However, Chi et al. found that although lower socioeconomic status was associated with food insecurity, the food insecurity was not associated with fast-food consumption. This had previously been postulated as a potential mechanism of linking food insecurity to caries considering that fast-foods are sources of added sugars, such as sugar-sweetened beverages.24 The relationship between caries and diet is complex, and there are contradictory theories regarding what constitutes a healthful diet.25 Some researchers have theorized that excessive carbohydrate intake, in the absence of preventive interventions, leads to dental disease followed by systemic disease.25 Conversely, others view lipids as a leading factor for systemic disease and promote high carbohydrate diets which can be misinterpreted as a recommendation for a diet consisting of highly refined carbohydrates.25
Social and cultural norms associated with foods influence food choices, preferences, beliefs, and behaviors23 adding to the complexity of food insecurity and influence on general as well as oral health. Food insecurity has been associated with increased rates of depression, diabetes, distress, and low medication adherence among adults with diabetes and an increased risk of opportunistic infections.26,27 Low food security has also been linked to increased incidence of hospitalizations among adults with HIV/AIDS.28 Food insecurity has been associated with nutrition-related conditions such as higher rates of parental overweight/obesity, fewer healthful mealtime foods, barriers to fruit and vegetable access, and increased binge eating.29
Unmet dental care need is an additional burden as well as a challenge for individuals with food insecurity. While there are a number of USDA programs addressing issues related to food insecurity, there is a need to examine the additional deficiencies contributing to the amount of unmet dental need for adults in the U.S.
Limitations of this study include the epidemiological cross-sectional research design which did not include temporality and therefore does not include causation. For the purposes of this study, the association between food insecurity and unmet dental need is presented as a relationship. While a number of factors were controlled in the adjusted analyses, there may have been confounders that were not available in the data set. The sample population may have had unmet dental need due to the distribution and availability of dental providers. Dietary patterns were not included in the sample population which would be helpful in identifying the mechanisms between the association of food insecurity and unmet dental care need. However, the study's strength comes from the nationally representative, highly regarded NHANES research. Dental examinations were completed by calibrated licensed dentists and the questionnaires were administered by extensively trained and calibrated researchers. While a larger sample size would have strengthened this study, multiple cycles of the NHANES did not include the same variables.
Conclusion
Food insecurity and health disparities present serious challenges to policy makers in the U.S.5 This study demonstrates a relationship between unmet dental care need and food insecurity. Dental professionals routinely query patients about their food intake due to its impact on oral and overall health, in addition to participating in community educational programs. Oral health care professionals should be aware of the various community food resource options available to individuals with low food security, make referrals to social service providers, and facilitate dental care for people with low food security through supportive policies to improve access to care.
About the Authors
R. Constance Wiener, MA, DMD, PhD is an associate professor, Department of Dental Practice and Rural Health, School of Dentistry; Usha Sambamoorthi, PhD is a professor, Department of Pharmaceutical Systems and Policy; both at West Virginia University, Morgantown, WV.
Monira Alwhaibi, PhD is an assistant professor, Department of Clinical Pharmacy, College of Pharmacy, King Saud University, Riyadh, Saudi Arabia
Chan Shen, PhD is an associate professor, Department of Health Services Research and Biostatistics, University of Texas MD Anderson Cancer Center, Houston, TX.
Patricia Findley, DrPH is an associate professor, Rutgers University School of Social Work, New Brusnwick, NJ.
Corresponding author: R. Constance Weiner, MA, DMD, PhD; rweiner2@hsc.wvu.edu
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