Cardiovascular diseases (CVDs) are diseases that affect the heart and blood vessels, presenting high mortality rates worldwide [1]. According to Oliveira et al. [2], about 30% deaths are caused by heart disease and represent a serious health problem in Brazil. Acute coronary syndrome (ACS) is a disease that affects the coronary arteries, generating an acute imbalance in the oxygen supply and demand in the cardiac muscle, which can lead to serious cardiovascular events, such as acute myocardial infarction (AMI) [1, 3].

The individual’s ability to acquire, process, and understand basic information and make self-care decisions with health is in the context of the definition of health literacy (HL), a descriptor originated from English HL and first cited by Simonds in 1974 [4, 5].

HL is an important social determinant; however, it is not only linked to the level of formal education of the individual, because the individual can present an adequate level of education and still not understand the medical guidelines on their health status [6]. Studies show that individuals with inadequate HL tend not to perform self-management satisfactorily of the disease of which they are a carrier, thus presenting higher hospitalization and mortality rates [7].

Due to the lack of instruments in the Portuguese language that assess the level of HL, researchers validated, for use in Brazil, the instrument Short Assessment of Health Literacy for Portuguese Speaking Adults (SAHLPA)-18, a test that performs the analysis of comprehension of individuals on medical terms commonly used in health [7].

The evaluation of HL in individuals with ACS is of great relevance because, in addition to being a chronic condition with high rates of morbidity and mortality globally, these subjects need adequate medical care after hospital discharge and uninterrupted care. Thus, an adequate understanding of the guidelines and health information determines the patient’s clinical outcome [6]. This data is scarce, and its impact on the group is little known in Brazil. The objective of this study is to evaluate the HL of patients with ACS, admitted to a high complexity hospital in the interior of Minas Gerais, Brazil, through the application of the SAHLPA-18 instrument.

The analysis included 175 patients who participated in the GCP project, hospitalized between August 2018 and March 2020, in a public hospital of high complexity in the interior of Minas Gerais state, Brazil.

The mean age of the patients was 58.02 years, and most of the participants were male (70.86%). The main comorbidities in patients with ACS were systemic arterial hypertension 51.43%, dyslipidemia 30.86%, and diabetes mellitus 24.00%, as shown in Table 1.

Regarding the clinical profile of the 175 patients included, 4.57% (n = 8) were diagnosed with unstable angina; 78.86% (n = 138) with AMI with ST-segment elevation [requiring > 1 mm of ST elevation at the J-point in two contiguous leads on the 12-lead electrocardiogram, ST-segment elevation myocardial infarction (STEMI) patients] [3]; and 16.57% (n = 29) with AMI without ST-segment elevation [all AMI patients without ST-segment elevation, or no STEMI (NSTEMI) patients]. Regarding life habits, 70.86% (n = 124) of the sample used tobacco, and 68.00% (n = 119) did not practice physical activity, as shown in Table 1.

Regarding the level of education, 51.43% of the participants had completed elementary school or higher education, while 48.57% were illiterate or had incomplete elementary school. As for family income, 54.86% of individuals had income above two minimum wages; in contrast, 45.14% had income less than or equal to two minimum wages, as shown in Table 1.

Despite the high level of education in the sample, we still observed a high rate of inadequacy in literacy, probably associated with other factors. Regarding the SAHLPA-18 instrument, adopting the criterion of 15 correct answers or more, 55.43% of individuals were considered with inadequate HL (97 among 175; 95% CI: 48.07–62.79). Among the patients who have completed elementary school or higher education, 40.00% of patients had inadequate HL (36 among 90).

Among the medical terms that make up the instrument, the items colitis, incest, and testicle had a higher percentage of mistakes, while the items convulsion, osteoporosis, and menstrual had a higher percentage of correct answers among the other test items, as shown in Table 2.

Concerning the predictive variables, in this study, the fact that the participant has completed elementary school or higher education, and/or has a family income higher than two minimum wages, increases by 12.66% and 5.90%, respectively, the percentage of correct responses in the SAHLPA-18 instrument, as shown in Table 3.

In addition, the fact that the individual is female and has completed elementary school or higher education level increases by 2.04 times (95% CI: 1.00 and 4.21) and 3.74 times (95% CI: 1.96 and 7.15), respectively, the chances of the individual having an adequate HL while the fact that the patient has diabetes mellitus decreases the chances in 0.42 times (95% CI: 0.19 and 0.95) of the client having an adequate HL, as shown in Table 4.

These results reinforce that formal education alone is not able to predict the HL of the sample. This reflects how other social (income) and personal aspects (sex and other disease presence) can interact together to define the literacy of these patients. We found that individuals of male sex, with diabetes, with incomplete primary education, or with less than two minimum wages show higher risks of inadequate HL, as shown in Table 5.

The sample was composed predominantly of male individuals, with a mean age of 58.02 years, with a diagnosis of AMI, life habits prone to smoking and sedentary lifestyle, with complete elementary school or higher education, and family income higher than two minimum wages, presenting, as main comorbidities, systemic arterial hypertension, diabetes mellitus, and dyslipidemia.

The occurrence of ACS predominantly in males, as evidenced in the study, can be explained by the poor preventive actions, more unhealthy risk factors, and poor lifestyle in this group [11, 12]. This fact may be directly related to the habits of life and the social construction of masculinity and invulnerability, linked to the thought that men tend to care less about health than women, which results in low demand for health prevention and promotion services by males. These factors reinforce the need for more effective health actions aimed at this public [11, 12], in particular males.

The average age of the current study was 58.02 years. This finding is similar to that found in the study by Chehuen Neto et al. [6], with chronic CVD carriers, with a mean age of 55 years. This demonstrates that the older the age, the greater the risks of developing CVDs, the higher the hospitalization rates, and the lower the chances of survival, then the age variable is considered a predictor of higher cardiovascular risks [13].

Systemic arterial hypertension, dyslipidemia, diabetes mellitus, and sedentary lifestyle are considered potential modifiable risk factors for the development of CVDs, including ACS. A study that analyzed the profile of Brazilian patients with CVDs also highlighted the comorbidities mentioned above, and systemic arterial hypertension had a higher prevalence (69.51%) [14]. The same occurred in the current study, with a prevalence of 51.43% [14].

Smoking is also a major modifiable risk factor that can lead to a fatal cardiovascular event. Evidence shows that individuals aged < 50 years and who use tobacco are 5 times more likely to develop a CVD [15]. Smoking cessation is one of the most effective preventive measures, significantly reducing the occurrence of AMI and morbidity and mortality rates due to CVD. Therefore, measures such as guidance on pharmacological therapy, providing individual and family support, and encouraging participation in collective or individual therapies can be effective health strategies in this rehabilitation process [16]. The presence of multifactorial risks gradually increases the chances of the individual being affected by an AMI. Thus, in order to reduce morbidity and mortality rates due to heart disease, cardiovascular risk prevention can occur in various ways, such as changing lifestyle, regular physical activity, adequate nutrition, and good adherence to pharmacological therapy [16].

Regarding the level of education of the participants, 51.43% of the study participants had completed elementary school or higher education, which differs from the literature. A study that also aimed to evaluate the functional HL of ACS patients of a cardiological hospital in Fortaleza, Brazil, using data from the GCP project, showed that about 52.6% of the sample had incomplete elementary education, and 85.5% of participants obtained inadequate HL from the analysis of the SAHLPA-18 instrument [17].

Chehuen Neto et al. [6] also analyzed the level of HL in patients with chronic CVDs, and the findings corroborate those of Costa et al. [17] regarding the prevalence of inadequate HL. The authors associate this finding with low education, low socioeconomic status, and the advanced age of the population studied. Another study that evaluated the HL of a diabetic population, using the SAHLPA-18 instrument, demonstrated that the lower the level of education, the lower the level of HL and, consequently, the glycemic control is inadequate [18]. The association between low literacy and diabetes is concerning in this group, as these patients are likely to have a poorer ability to process health education and change behaviors. Over time, they are also expected to have lower adherence to treatments, leading to worse outcomes, especially for conditions like heart diseases and stroke, for which diabetes itself is already a risk factor.

In the present study, although 51.43% of the participants had completed elementary school or higher education, 55.43% of the participants had inadequate HL, as measured by the SAHLPA-18 instrument. Apolinario et al. [7] showed in their study that, although 30% of the elderly in the sample had a high school education, they presented inadequate HL through the SAHLPA-18 instrument, leading to the conclusion that it is not possible to assume that every individual with a good level of formal education will present appropriate HL. This means that even with a good level of formal education, individuals are not always able to effectively understand their disease and state of health, the importance of good adherence to pharmacological treatment and the adoption of preventive measures, communication with health professionals, and their ability to put into practice medical guidelines [19]. These factors become even more critical in a scenario where risk factors are modifiable, and the capacity to understand health education may be impaired.

Although seen in this study that the degree of formal education of individuals will not always predict that they will have adequate HL, when performing a survey of the variables that predicted a higher percentage of success in the SAHLPA-18, as seen in Table 3, the variables schooling and family income were highlighted. Thus, it is concluded that the better the level of education and financial conditions of individuals, the greater the chances of them presenting adequate HL; however, even in this scenario, these individuals will not always have a good HL [20]. Eventually, in this population, individuals with high formal education are uncommon, due to the public nature of the institution; although in Brazil, the population with graduate and postgraduate degrees is still a minority.

In association with the aforementioned variables, in the current study, belonging to the female sex was also considered a weight factor for a good HL. This finding corroborates those found in other studies, which can be explained by the fact that women tend to seek health services more in relation to the male population and are more aware of their health status [6].

A peculiar variable, evidenced in the study, which negatively impacted the HL is the fact that the participant has diabetes mellitus. This can be justified by the cognitive damage that can occur throughout the development of the disease. The literature shows that patients with type 2 diabetes mellitus are more prone to cognitive impairment caused by oxidative stress, inflammation, macro and microvascular changes, and accumulation of neurotoxic substances promoted by the disease, neurological changes, and impairment of some brain functions, such as attention and memory. In addition, there may be a decrease in the speed of information processing, which significantly influences the patient’s process of understanding about his/her health situation [21–23].

We emphasize that health professionals should assess their patients’ literacy. Without this information, the entire process of health education, post-discharge guidance, and even treatment adherence can be compromised, resulting in the worst outcomes. Our data also reinforce that even patients with some level of formal education may have impaired HL and demand specific health education, which can be further exacerbated by the presence of diabetes. Understanding patients’ literacy and its associated factors can allow for a better proposal of their care plan. HL also improves the quality of life, enhancing self-management, treatment adherence, decreasing CVD hospital admissions, and reducing costs to the public health sector in ACS patients [24, 25]. Positive significant associations also were observed between HL and levels of health system competence, social support, cardiac self-efficacy, and health-related quality of life [26].