Health literacy assessment of individuals with and without Chagas disease: a cross-sectional study
Chagas Disease (ChD) is considered a neglected disease with a high rate of morbidity and mortality. It is estimated to affect 6 to 7 million people worldwide and cause 50,000 deaths per year, in addition to substantial social impact, such as compromising the quality of life (QoL) of affected individuals . There is evidence that ChD is more prevalent in socioeconomically vulnerable individuals with low health literacy, which limits their ability to understand health information and engage in self-care . It is known that promoting self-care is an important strategy and tool in healthcare services, especially those focused on chronic conditions. However, its success depends on individuals’ ability to comprehend information. Effective self-care leads to better health outcomes and is associated with adequate health literacy . Literacy, or health literacy, is defined as “the degree to which individuals have the capacity to obtain, process, and understand basic health information and services needed to make appropriate health decisions“ . Health literacy depends not only on individuals but also on the ability of organizations to make health-related information and services accessible and understandable, enabling people to engage in self-care . Evidence indicates that low health literacy is associated with higher rates of hospitalizations, lower utilization of preventive services, increased use of emergency services, reduced ability to manage medication and understand health instructions, and higher mortality rates . Therefore, it is important for healthcare professionals to employ strategies that can minimize the consequences of low health literacy in the care process . Sørensen et al. (2015) further emphasize that health literacy should be taken into account when developing public health strategies to improve equity . Due to its relevance in the field of public health, investigations on health literacy have attracted the attention of the scientific community . However, in individuals with ChD, studies related to health literacy are still scarce. In the study by Quintino et al. (2020a), the prevalence of inadequate health literacy was 85.1% in patients with chronic ChD . Furthermore, participants with inadequate health literacy had worse cardiovascular outcomes and a higher need for medication use. Given the limited studies and the importance of this indicator for care planning, it is highly relevant to understand the health literacy profile of individuals with ChD and compare it to those without the disease. Therefore, our objective was to assess health literacy and its association with sociodemographic, clinical, and QoL characteristics. 

This is a cross-sectional study conducted within a cohort study. The study originated from the National Epidemiology Study of Retrovirus Donors II (REDS II). The REDS II was a retrospective cohort study in which 511 donors were enrolled from two blood centers (Fundação Pró-Sangue (SP) and Hemocentro de Montes Claros (MG) who were confirmed positive for T cruzi antibody at the time of blood donation in 1998 to 2002 and 504 seronegative donors. As described by Sabino et al. (2013) in São Paulo, performed T cruzi antibody screening in 1996 to 2002 that consisted of 3 serological methods: ELISA, hemaglutination, and immunofluorescence. For the purpose of this study, we included confirmed Chagas donors who were positive by all 3 assays at the time of donation. In Minas Gerais, Montes Claros, the blood center screened all donations with 2 serological assays: ELISA and hemaglutination. Donors reactive to both assays at the time of donation were considered eligible for this study . Ten years after blood donation, from July 2008 to October 2010, these donors were invited to participate in the study. During this visit, blood samples were collected, and participants underwent an electrocardiogram (ECG) and echocardiogram (ECO). Three different ELISA screening tests kits for diagnosis of Chagas and a PCR were performed for all participants . They also completed a questionnaire that included sociodemographic variables (sex, blood center, age, income, and skin color) and clinical variables (summary ECG measurement, ejection fraction, presence of cardiomyopathy, medication use, and Pro-BNP levels). The presence of cardiomyopathy was classified based on the following criteria: left ventricular ejection fraction < 50% or QRS interval ≥ 120ms . The left ventricular ejection fraction was classified as abnormal if < 50% and normal if > 50%. The classification of the summary ECG measurement was based on the major and minor abnormalities defined by Denes et al. (2007) and cited by Sabino et al. (2013) . The questionnaire used in this study was also used in the work of Baldoni et al. (2023) . In a second visit conducted in 2018–2019, these participants were interviewed again. During this visit, the same outcomes were reassessed, and measures of health literacy and QoL were obtained. The SALPHA-18 instrument was used to evaluate health literacy. This instrument consists of 18 questions presented to participants using cards with a medical term followed by two associated words, with only one word correctly associated with the term. The response was considered correct when the participant could read the medical term correctly and associate it with the correct word. A score of ≤ 14 points classified the individual as having inadequate health literacy, while a score > 15 indicated adequate health literacy . Only individuals who reported being able to read and write completed the SALPHA-18, while those who were unable to read and write were classified as illiterate. Thus, the health literacy variable was grouped into three categories: (1) adequate literacy, (2) inadequate literacy, and (3) illiterate. The WHOQOL-Bref scale, validated in Brazil, was used to assess QoL. This instrument comprises four domains: (1) Physical, (2) Psychological, (3) Social Relationships, and (4) Environment. Each domain is evaluated using a Likert-type scale ranging from 0 to 100 points, with higher scores indicating a better perception of QoL . Participants were included in the study if they were capable of understanding the questions of the instrument and self-assessing their QoL. Statistical analysis The descriptive analysis involved calculating absolute and relative frequencies for categorical variables, and means and standard deviations for quantitative variables. To assess the association between sociodemographic, clinical, and QoL domain variables and the literacy in health response, ordinal logistic regression models assuming proportional odds ratios were fitted. Initially, simple regression models were constructed to test the association of each variable with the response. Subsequently, multiple models were adjusted, with only statistically significant variables remaining in the final model. Odds ratios and confidence intervals were considered as the effect measure. Multicollinearity among potential predictors was assessed using the variance inflation factor (VIF). The assumption of proportional odds ratios was tested using the likelihood ratio test. As the income variable had a large amount of missing data (152 individuals or 24.9% of the total), an imputation analysis was conducted. Based on an exploration of the relationship between non-response in income and observed variables, all variables were used in the imputation model. To a lesser extent, missing values were also observed for skin color (2 individuals), ejection fraction (1 individual), and number of medications in use (6 individuals). For generating imputations, income, age, and QoL domain variables were considered in their continuous versions and subsequently discretized for model fitting. Specifically, given its skewed distribution, income was logged. A total of 200 imputations were generated for each missing value based on a normal (Bayesian) model for logged income, a polytomous logistic model for skin color and number of medications in use, and a binary logistic model for ejection fraction. The results of the ordinal logistic regression model fit in the 200 imputed datasets were combined using Rubin’s rules for multiple imputation. A significance level of 5% was considered in all analyses. All statistical analyses were performed using the open-source software R, version 4.2.2, using the tidyverse and haven packages for data reading and manipulation, mice and mitools packages for multiple imputation, and the VGAM package for regression model fitting. Ethical aspects This investigation was approved by the Research Ethics Committee (CEP) of the University of São Paulo (USP), under protocol number 6023, 042/12 and CAAE: 00580612.8.0000.0065, and by the National Committee of Ethics in Research (CONEP), protocol number 1312/2006. The research was carried out in agreement with Guidelines and Regulations for Research Involving Human Beings (CONEP Resolution N o 466/2012). 

The descriptive analysis involved calculating absolute and relative frequencies for categorical variables, and means and standard deviations for quantitative variables. To assess the association between sociodemographic, clinical, and QoL domain variables and the literacy in health response, ordinal logistic regression models assuming proportional odds ratios were fitted. Initially, simple regression models were constructed to test the association of each variable with the response. Subsequently, multiple models were adjusted, with only statistically significant variables remaining in the final model. Odds ratios and confidence intervals were considered as the effect measure. Multicollinearity among potential predictors was assessed using the variance inflation factor (VIF). The assumption of proportional odds ratios was tested using the likelihood ratio test. As the income variable had a large amount of missing data (152 individuals or 24.9% of the total), an imputation analysis was conducted. Based on an exploration of the relationship between non-response in income and observed variables, all variables were used in the imputation model. To a lesser extent, missing values were also observed for skin color (2 individuals), ejection fraction (1 individual), and number of medications in use (6 individuals). For generating imputations, income, age, and QoL domain variables were considered in their continuous versions and subsequently discretized for model fitting. Specifically, given its skewed distribution, income was logged. A total of 200 imputations were generated for each missing value based on a normal (Bayesian) model for logged income, a polytomous logistic model for skin color and number of medications in use, and a binary logistic model for ejection fraction. The results of the ordinal logistic regression model fit in the 200 imputed datasets were combined using Rubin’s rules for multiple imputation. A significance level of 5% was considered in all analyses. All statistical analyses were performed using the open-source software R, version 4.2.2, using the tidyverse and haven packages for data reading and manipulation, mice and mitools packages for multiple imputation, and the VGAM package for regression model fitting. 

This investigation was approved by the Research Ethics Committee (CEP) of the University of São Paulo (USP), under protocol number 6023, 042/12 and CAAE: 00580612.8.0000.0065, and by the National Committee of Ethics in Research (CONEP), protocol number 1312/2006. The research was carried out in agreement with Guidelines and Regulations for Research Involving Human Beings (CONEP Resolution N o 466/2012). 

A total of 611 participants took part in the study, including 328 with ChD and 283 without the disease. Four individuals were excluded due to missing information on the QoL scale. Figure summarizes the selection of the study population. Regarding losses due to death during the follow-up between the first and second visits, there were 32 deaths among seropositive participants and 18 deaths among seronegative participants, as described in the study by Nunes et al. (2021) . As shown in Fig. , the proportion of adequate health literacy, inadequate health literacy, and illiteracy among individuals with the disease was 40.2%, 65.5%, and 76.1%, respectively. In contrast, among individuals without ChD, the proportion was 59.8%, 34.5%, and 23.9%. It can be observed that among people with ChD, there is a higher proportion of inadequate health literacy and illiteracy compared to individuals without the disease (Fig. ). Table presents the sociodemographic, clinical, and QoL characteristics of the participants. Among the 611 participants, the majority were female (51.4%), from the hemocenter in Minas Gerais (54.3%), aged < 56 years (53.7%), had a family income < R$2,200 (54.7%), and self-identified as black/mixed race (59.4%). Regarding clinical characteristics, the majority of participants had ChD (53.7%). Approximately half of the individuals had minor ECG abnormalities (48.3%). Cardiomyopathy was present in 17.8% of participants. Furthermore, 16.0% of the study population reported using three or more medications. Regarding QoL, the median scores were 75.0 in the Physical, Psychological, and Social Relationships domains. The median score was slightly lower, at 68.75, in the Environment domain. In the bivariate analysis, it was observed that individuals with better literacy were from the hemocenter in São Paulo (SP), OR: 3.26 [2.36–4.5]; younger (< 56 years), OR: 1.80 [1.32–2.45]; and had higher income (≥ R$2,200), OR: 3.92 [2.7–5.68]. In contrast, individuals with poorer literacy were patients with minor ECG abnormalities, OR: 0.59 [0.38–0.90], and major abnormalities, OR: 0.50 [0.32–0.79]; abnormal ejection fraction, OR: 0.46 [0.24–0.90]; and those using three or more medications, OR: 0.56 [0.36–0.88]. Lower health literacy was observed in individuals with scores < 75.0 in the Physical domain, OR: 0.73 [0.54–0.99]; Psychological domain, OR: 0.73 [0.53–0.99]; and in individuals with scores < 68.75 in the Environment domain, OR: 0.43 [0.31–0.58]. No association with health literacy was found for the variables of sex, presence of cardiomyopathy, and levels of age-adjusted pro-BNP ( p > 0.05). Table presents the results of the analyses with imputed data for the initial and final models. The final model shows that better literacy was found in individuals who were female, OR: 1.91 [1.34–2.71]; residents of São Paulo, OR: 3.15 [2.09–4.75]; younger, OR: 3.05 [2.12–4.39]; higher income, OR: 2.93 [2.04–4.21]; white race (compared to black/mixed race), OR: 1.64 [1.10–2.44]; and in individuals without ChD, OR: 3.78 [2.65–5.41]. An analysis of the imputed data for the income variable was conducted, dividing participants into two groups: those with reported income and those without. When examining the proportions, it is noted that the proportion of participants with reported income was 98.8% in the Minas Gerais blood center and 47.0% in the São Paulo blood center (< 0.001). Furthermore, the proportion of participants with reported income was 66% among those with adequate health literacy, 84% among those with inadequate health literacy, and 86.4% among illiterate individuals (< 0.001). The proportion of participants with reported income was 58.0% among those with white skin color, 75% among those with other skin colors, and 85% among those with black or mixed race (< 0.001). The proportion of participants with reported income was higher among younger individuals ( p = 0.006) (Supplementary Material 1). 

In this investigation, being female, living in São Paulo, younger age, higher income, white skin color, and absence of ChD were characteristics associated with better health literacy. A high proportion of inadequate health literacy and illiteracy was observed among individuals with ChD. In addition to individuals with ChD being more vulnerable, having lower purchasing power, and lower subjective perception of QoL, the results of the present study demonstrate that these individuals also have lower health literacy compared to individuals without this clinical condition . When analyzing inadequate health literacy in European countries, the prevalence ranged from 29 to 62% . The prevalence of inadequate health literacy in individuals with ChD is higher, as evidenced in this study (65.5%) and in the study by Quintino et al. (2020a) (85.1%) . However, the rate of illiteracy is similar (76.1% versus 74.1%, respectively). The difference in inadequate health literacy between this investigation and the study by Quintino et al. may be related to the origin of the participants. In the present investigation, the included patients are from two blood centers, while in the Quintino et al. study, the patients were from primary healthcare in remote regions of Minas Gerais. The findings of this study demonstrate a substantial association between health literacy and socioeconomic and demographic characteristics. Higher income is associated with better health literacy. The study by Stormacq et al. (2018) also showed that disadvantaged socioeconomic conditions contribute to low levels of health literacy. Moreover, low health literacy can influence health behaviors, lower QoL, and the timely use of preventive services . Therefore, it is of great importance to invest in effective public policies that address income distribution, education, and clear health information targeted at this population. Regarding income, it was observed that many participants in the study did not respond to the question about income, and therefore the data were imputed. It is noteworthy that individuals who were less likely to report their income were from the São Paulo hemocenter, had better health literacy, white skin color, and were younger. This could be a profile of participants who have higher income and chose not to respond to this research question. Another variable associated with low health literacy was age, as younger people had better health literacy. This may be related to limited educational opportunities for older birth cohorts, especially in regions with low social indicators. In this regard, it was observed that participants from the São Paulo hemocenter had better health literacy. This could be attributed to greater access to information and healthcare services compared to participants living in the Montes Claros region, as São Paulo is a more populous and economically developed urban center with higher tax revenue allocated to investments in basic education . It is known that educational attainment is an important determinant of health literacy . Given the sociodemographic, clinical, and QoL characteristics identified as associated with lower health literacy in patients with ChD, it emphasizes the importance of timely diagnosis and treatment to prevent disease progression to the chronic phase, which can unfavorably affect QoL. It is known that approximately 30% of infected individuals may progress to clinical forms of the disease, particularly cardiovascular manifestations such as Chagas cardiomyopathy, which can lead to disability and even death . However, there are many challenges to ensuring timely treatment for ChD, including uncertainties among medical professionals regarding the administration of antiparasitic treatment in the chronic phase of the disease . In this regard, educational institutions, as providers of human resources, can plan their curricula to equip professionals with greater expertise in the entire care process, from screening to the treatment of neglected diseases such as ChD. In the context of the care process, it is important for the healthcare team to be aware of low health literacy, particularly among populations affected by neglected diseases, as it reduces the likelihood of individuals seeking timely healthcare and can create barriers to accessing necessary care . Therefore, actively identifying individuals with risk factors for ChD (e.g., living in endemic regions) can contribute to providing comprehensive care at the right time, thus preventing complications associated with the disease. Health education actions should be carried out to improve access to health information for individuals with ChD. In this regard, it is important for healthcare professionals to assess the health literacy level of patients before delivering information and, if necessary, employ interactive strategies that empower this population. It is believed that such strategies can enhance understanding among patients with low health literacy, enabling them to apply this information in their daily lives, such as identifying the ChD vector, the Triatominae (Triatoma sp.). Additionally, during the treatment phase, creating pictograms to explain medication dosage and differentiate drug classes can be beneficial. By using simple and easily understandable strategies, we can promote health equity and encourage greater self-care among individuals with ChD. This work stands out for its originality in presenting evidence on literacy among individuals with and without ChD. 

The findings of this study highlight a high prevalence of inadequate health literacy and illiteracy among patients with ChD. Patients with better health literacy were predominantly female, living in metropolitan area, younger, with higher income, white, and without ChD. The low health literacy identified in this study highlights the need to improve communication between professionals and patients, aiming for clearer health information that can be used by users for self-care. 

Below is the link to the electronic supplementary material. Supplementary Material 1 

