https://orcid.org/0000-0003-4722-6894
Figures
Abstract
Background
Health literacy (HL) is a key determinant of physical and mental health outcomes; however, the relationships among HL, anxiety symptoms, and health-related quality of life (HRQoL) remain unclear, and whether the effects of HL vary by age is unknown. We aimed to examine the associations among HL, anxiety symptoms, and HRQoL in Korean adults and assessed age-related differences in these associations.
Methods
In this cross-sectional study, we analyzed data from the 2023 Korea National Health and Nutrition Examination Survey, including 5,017 adults aged ≥ 19 years. HL was assessed using a validated 10-item instrument (score range: 10–40) and categorized as low, middle, or high. Anxiety symptoms and HRQoL were measured using the 7-item Generalized Anxiety Disorder Scale and the 8-item Health-related Quality of Life Instrument, respectively. Multivariable logistic regression models adjusted for potential confounders were used to estimate associations between HL and anxiety symptoms and between HL and good HRQoL. Age-stratified analyses were conducted for participants aged 19–39, 40–64, and ≥ 65 years.
Results
The low (odds ratio [OR]: 1.93; 95% confidence interval [CI]: 1.52–2.46; p < 0.001) and middle HL (OR: 1.30; 95% CI: 1.04–1.62; p = 0.024) groups had higher odds of anxiety symptoms than the high HL group. Lower HL was associated with a reduced likelihood of good HRQoL (OR: 0.49; 95% CI: 0.36–0.66; p < 0.001), whereas the middle HL group showed a non-significant trend toward poorer HRQoL (OR: 0.77; 95% CI: 0.56–1.06). HL was associated with anxiety symptoms in young and middle-aged adults, and with HRQoL in young and older adults.
Citation: Seol G, Hwangbo Y, Kim Y, Chang Y, Lee M-R (2026) Associations among health literacy, anxiety symptoms, and health-related quality of life in Korean adults: A cross-sectional study with age-stratified analyses. PLoS One 21(2): e0342239. https://doi.org/10.1371/journal.pone.0342239
Editor: Muhammad Shahzad Aslam, Xiamen University - Malaysia Campus: Xiamen University - Malaysia, MALAYSIA
Received: September 17, 2025; Accepted: January 20, 2026; Published: February 9, 2026
Copyright: © 2026 Seol et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Data Availability: The data underlying the results presented in this study are publicly available from the Korea National Health and Nutrition Examination Survey (KNHANES) website (https://knhanes.kdca.go.kr/). All data are fully available without restriction.
Funding: This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIT) (RS-2025-23323371) and the Soonchunhyang University Research Fund. There was no additional external funding received for this study.
Competing interests: The authors have declared that no competing interests exist.
Introduction
Health literacy (HL) refers to an individual’s ability to access, understand, appraise, and apply health-related information and services to make appropriate health decisions and take informed actions. The World Health Organization (WHO) characterizes HL as a stronger predictor of health status than socioeconomic factors, such as income and educational attainment [1]. Higher HL is associated with effective personal health management, improved health indicators, and broader social benefits [2]. In contrast, limited HL is associated with poorer health outcomes, including worse overall health status [3], reduced use of preventive services [4], more frequent hospital admissions [5], and increased mortality [6]. Despite its importance low HL remains common across populations. In Korea, approximately 55.4% of adults have been classified as having limited HL [7], indicating a significant public health concern, even within a highly educated society [8].
In the United States, nearly half of adults have limited HL [9]. In Europe, at least 12% of respondents demonstrate insufficient HL, and almost half (47%) are classified as having limited HL, defined as insufficient or problematic HL [10]. Limited HL may hinder access to health information and contribute to delayed care and increased anxiety.
Low HL is associated with a higher prevalence of anxiety symptoms [11,12]. However, most previous studies have focused on mental HL, and only a few have directly examined the association between HL and anxiety symptoms [13,14]. Therefore, evidence clarifying the relationship between these two variables remains limited [15,16].
In addition to mental health outcomes, HL may influence perceived health-related quality of life (HRQoL) [17,18]. HRQoL reflects an individual’s perception of quality of life within cultural and social contexts [19] and is widely used to evaluate the impact of medical interventions and population-based health surveys [20]. Higher HL has been associated with better HRQoL [21,22]; however, findings remain inconsistent. For example, a longitudinal study of Canadian patients with type 2 diabetes reported that lower HL was associated with poorer HRQoL [23]. In contrast, a study of Chinese patients with chronic heart failure found no significant association between these variables [24]. These inconsistencies may reflect differences in study populations. Previous research has primarily focused on patients with specific conditions or on particular age groups, such as older adults, adolescents, and young adults [17,18]. In addition, some studies were conducted in specific contexts, such as during the Coronavirus Disease 2019 (COVID-19) pandemic [16,25], which may limit the generalizability of their findings. To date, studies examining the simultaneous effects of HL on anxiety symptoms and HRQoL remain scarce, particularly in general adult populations [26–28].
Furthermore, the relationship between HL and age remains unclear. Some studies have reported lower HL among older adults [29,30], whereas others have observed no clear age-related trend or even lower HL among younger individuals [31,32]. These inconsistencies highlight the need to clarify how HL influences mental health and the quality of life across different age groups.
Therefore, in this current study, we utilized data from the 2023 Korea National Health and Nutrition Examination Survey (KNHANES) to examine differences in anxiety symptoms and HRQoL according to HL levels among Korean adults. Furthermore, we assessed whether the associations among HL, anxiety symptoms, and HRQoL varied by age. We aimed to provide empirical evidence on the relationship between HL, mental health, and quality of life and to generate foundational data to inform the development of age-specific interventions to improve HL and overall well-being.
Conceptual framework
This study was guided by a conceptual framework outlining the hypothesized relationships among HL, anxiety symptoms, and HRQoL (Fig 1). We hypothesized that lower HL is associated with greater anxiety symptoms and poorer HRQoL through several potential mechanisms, including difficulty understanding and applying health information, reduced self-management capacity, a higher burden of chronic disease, and differences in healthcare utilization. Age was conceptualized as an effect modifier, such that the strength and relevance of these pathways may vary across young, middle-aged, and older adults. This framework provides the rationale for the age-stratified analyses and supports interpretation of the observed associations in this cross-sectional study.
This framework depicts potential mechanisms through which health literacy may influence anxiety symptoms and HRQoL, including cognitive and self-management capacity, chronic disease burden, and healthcare utilization, based on prior literature. Age group is conceptualized as a moderating factor that may influence these pathways. Arrows represent hypothesized relationships and do not imply causal or mediation effects.
Materials and methods
Study design
This study is a cross-sectional observational analysis based on data from the 2023 KNHANES. We conducted a secondary analysis of a nationally representative sample of Korean adults. HL was treated as the exposure variable, and anxiety symptoms and HRQoL were treated as outcome variables. Given the cross-sectional design, temporal relationships between HL and the outcomes could not be established. Because a fixed sample from the 2023 KNHANES was used in this study, an a priori sample size calculation was not feasible.
Data collection and study population
This study was based on data from the second year of the ninth KNHANES cycle (2023), a nationally representative survey conducted annually by the Korea Disease Control and Prevention Agency (KDCA) under the National Health Promotion Act.
KNHANES employs a stratified, multistage probability sampling design to ensure representativeness of the Korean population aged 1 year and older. The survey comprises three components: health interviews, health examinations, and nutrition surveys. All procedures were approved by the relevant Institutional Review Board, and the public-use dataset was anonymized to protect participant confidentiality. We accessed the 2023 KNHANES data on February 7, 2025, through the KDCA.
The initial sample included 6,929 participants. After excluding individuals younger than 19 years (n = 1,022) and those with missing data on covariates (n = 889) or the Generalized Anxiety Disorder-7 (GAD-7) scale (n = 1), the final analytical sample comprised 5,017 adults (Fig 2).
Flowchart showing the selection of study participants from the 2023 Korea National Health and Nutrition Examination Survey (KNHANES). Of the 6,929 participants initially assessed, those aged younger than 19 years (n = 1,022), those with missing covariate data (n = 889), and one participant with missing data on the Generalized Anxiety Disorder-7 (GAD-7) scale were excluded. The final analytical sample comprised 5,017 adults.
Ethics statement
The 2023 KNHANES was conducted in accordance with the Declaration of Helsinki, and all participants provided informed consent.
We analyzed only anonymized, publicly available data.
The Institutional Review Board of the Soonchunhyang University Hospital approved the study protocol (IRB No. 2025-05-042-001).
Exposure variable
HL
The primary independent variable was HL, which was assessed using a validated 10-item instrument newly introduced in the 2023 KNHANES [33]. This instrument was developed specifically for the Korean healthcare context. Each item was rated on a 4-point Likert scale ranging from “strongly disagree” (1) to “strongly agree” (4). The instrument comprises four domains: disease prevention (three items), healthcare (four items), health promotion (one item), and resource utilization (two items). Total scores range from 10 to 40, with higher scores indicating higher HL. The instrument demonstrated high internal consistency (Cronbach’s α = 0.87). HL scores were classified into three levels based on cutoff points proposed in the original validation study of the KNHANES health literacy index [33]: low (≤ 28), middle (29–31), and high (≥ 32).
Outcome variables
GAD-7
Generalized anxiety symptoms during the past 2 weeks were assessed using the validated Korean version of the GAD-7 scale, a screening instrument used to identify individuals at risk for generalized anxiety disorder. Total scores range from 0 to 21, with higher scores indicating greater symptom severity. Consistent with previous KNHANES-based research, a cutoff score of ≥ 5 was used to define elevated anxiety symptoms [34,35].
HRQoL
HRQoL was assessed using the Health-Related Quality of Life Instrument with eight Items (HINT-8), a preference-based instrument developed for the Korean population. The HINT-8 comprises eight items assessing multiple domains, including climbing stairs, pain, vitality, work performance, depressive mood, memory, sleep quality, and happiness. Each item is rated on a 4-point Likert scale. A utility index score ranging from 0 to 1 was calculated by applying preference weights to participant responses, with values closer to 1 indicating better quality of life [36]. In the KNHANES, HRQoL is evaluated using a biennial rotation of the EuroQol-5 Dimension instrument and the HINT-8. The HINT-8 was administered in the 2023 survey, and index scores were derived from participants’ HINT-8 responses [37]. Observed scores ranged from 0.303 to 0.927. In the absence of an established clinical cutoff, participants with scores in the lowest decile (< 0.688) were classified as having low HRQoL, consistent with previous research [38].
Covariates
Several demographic and health-related variables were included as covariates. Age was categorized into three groups: 19–39 years, 40–64 years, and ≥ 65 years [39,40]. Other demographic variables included sex (male or female, with female as the reference category), marital status (married or unmarried), educational attainment (less than high school, high school graduate, or college graduate or higher), and household income (quartiles).
Female sex was selected as the reference category to maintain consistency with previous KNHANES-based studies and because women slightly outnumbered men in the study sample. Health behavior variables included smoking status (current smoker: defined as having smoked at least 100 cigarettes in one’s lifetime and currently smoking, or non-current smoker) and alcohol consumption (drinking ≥ once per month). Aerobic physical activity adherence was defined as engaging in ≥ 150 min of moderate-intensity physical activity per week, or ≥ 75 min of vigorous-intensity physical activity per week, or an equivalent combination of both [41].
Healthcare utilization and chronic disease burden were also considered. Outpatient visits within the past 2 weeks and inpatient hospitalizations during the past year were coded as “yes” or “no.” Chronic disease burden was quantified as the number of physician-diagnosed chronic conditions reported from a predefined list of eight common conditions: hypertension, diabetes mellitus, asthma, chronic rhinosinusitis, allergic rhinitis, obstructive sleep apnea, chronic kidney disease, and dyslipidemia [42]. Data on key mental health variables such as depression and perceived stress were not available in the 2023 survey cycle and therefore could not be included as covariates in the analysis.
Statistical analyses
All statistical analyses were conducted in accordance with the KNHANES Analytic and Reporting Guidelines using a complex survey design. Sampling weights, stratification variables, and primary sampling units were applied in all analyses to account for the stratified, multistage probability sampling design of KNHANES. Descriptive statistics for participant characteristics and group comparisons were performed using the chi-square test.
For the primary analyses, HL was treated as a three-level categorical variable (low: ≤ 28; middle: 29–31; high: ≥ 32). Anxiety symptoms (GAD-7 ≥ 5) and HRQoL (HINT-8 < 0.688) were dichotomized using validated cutoffs.
Associations between HL and the outcomes (anxiety symptoms and HRQoL) were examined using multivariable logistic regression models to estimate odds ratios (ORs) with 95% confidence intervals (CIs). Models were adjusted for covariates described above, including age, sex, marital status, educational attainment, income quartile, smoking status, alcohol consumption, physical activity, chronic disease burden, and outpatient/inpatient health care utilization. Subgroup analyses were conducted to examine age-specific associations. All statistical tests were two-sided, and a p-value < 0.05 was considered statistically significant. Statistical analyses were performed using Stata version 14 (StataCorp, College Station, TX, USA). Multicollinearity among covariates was examined using variance inflation factors, and no significant problematic multicollinearity was detected.
Results
Study population characteristics
A total of 5,017 participants were included in the analysis (mean age: 53.3 ± 16.5 years; 43.1% male). HL levels were distributed as follows: low (n = 1,551), middle (n = 1,799), and high (n = 1,667).
Table 1 summarizes the general characteristics of the study population by HL level. HL differed significantly across age groups. Among participants in the 19–39 years age group, 56.1% were classified as having high HL. In contrast, among those aged ≥ 65 years, only 8.8% had high HL, whereas 33.4% had low HL.
Higher HL was more prevalent among females; individuals with higher educational attainment; those in the highest income quartile; current smokers; alcohol consumers; married individuals; participants meeting aerobic physical activity guidelines; those without recent outpatient or inpatient health care utilization; and those with a lower chronic disease burden.
The prevalence of anxiety symptoms, defined as a GAD-7 score ≥ 5, was highest in the low HL group (20.0%), compared with the middle (15.4%) and high HL groups (14.6%) (p < 0.001). Similarly, the prevalence of low HRQoL was greater among participants with low HL (14.1%) than among those with high HL (4.2%) (p < 0.001).
Association between HL, anxiety symptoms, and HRQoL
Table 2 shows that the low (OR: 1.93; 95% CI: 1.52–2.46; p < 0.001) and middle HL (OR: 1.30, 95% CI: 1.04–1.62; p = 0.024) groups had significantly higher odds of anxiety symptoms than the high HL group. Lower HL was associated with a reduced likelihood of good HRQoL; the low HL group showed significantly lower HRQoL than the high HL group (OR: 0.49; 95% CI: 0.36–0.66; p < 0.001). The middle HL group showed a nonsignificant trend toward lower HRQoL (OR: 0.77; 95% CI: 0.56–1.06; p = 0.115). In addition, sex, smoking status, healthcare utilization, and chronic disease burden were significantly associated with both anxiety symptoms and HRQoL.
Associations between HL and anxiety symptoms by age group
As shown in Table 3, low HL was associated with higher odds of anxiety symptoms among young adults (OR: 2.34; 95% CI: 1.62–3.37; p < 0.001) and middle-aged adults (OR: 1.92; 95% CI: 1.34–2.75; p < 0.001). In contrast, no significant association was observed among older adults (aged ≥ 65 years).
Associations between HL and HRQoL by age group
As shown in Table 4, both low (OR: 0.30; 95% CI: 0.15–0.58; p < 0.001) and middle HL (OR: 0.53; 95% CI: 0.28–0.99; p = 0.049) were significantly associated with poorer HRQoL among young adults (19–39 years).
No significant association between HL and HRQoL was observed among middle-aged adults (40–64 years). In contrast, among older adults (≥ 65 years), low HL was significantly associated with poorer HRQoL (OR: 0.58; 95% CI: 0.34–0.97; p = 0.040).
Discussion
In this study, we analyzed a nationally representative sample of Korean adults and found that lower HL was significantly associated with higher odds of anxiety symptoms and lower HRQoL. Age-stratified analyses further demonstrated that these associations differed across young, middle-aged, and older adults.
These findings are consistent with previous evidence linking lower HL to higher levels of anxiety [11].
For example, the EUROASPIRE V multinational cross-sectional survey of patients with coronary heart disease reported a significant association between lower HL and higher anxiety levels [43]. Similarly, a cross-sectional descriptive-analytical study conducted in Khuzestan, Iran, among adults aged 18–65 years found that lower HL was significantly associated with increased anxiety symptoms [16].
The HRQoL findings also align with those reported in previous studies. A cross-sectional study in Germany reported that low HL was associated with poorer HRQoL [44], while a study of Korean adults with chronic diseases found that adequate HL was associated with higher HRQoL [7]. However, studies involving patients with heart failure have not consistently identified a significant association between HL and HRQoL, indicating that this relationship remains inconclusive [24]. Therefore, the present study, conducted in a nationally representative adult population, contributes to a broader understanding of the inconsistent findings reported in previous studies. Additional evidence of age-specific differences in the associations among HL, anxiety symptoms, and HRQoL, was also provided.
Among young adults, lower HL was associated with higher odds of anxiety symptoms and poorer HRQoL. Young adulthood is characterized by social identity formation, career exploration, and the pursuit of financial independence, all of which may expose individuals to significant psychosocial stressors [45]. These challenges may be particularly difficult for individuals with low HL [46]. In Korea, suicide has been reported as the leading cause of death among individuals aged 20–30 years, highlighting the vulnerability of this age group with respect to mental health [47]. Moreover, in the present study, we used data from 2023, reflecting the post–COVID–19 socioeconomic context. The prolonged pandemic contributed to economic contraction and employment instability, intensifying job insecurity among young adults [48,49]. Employment rates have gradually recovered worldwide; however, Korea’s employment rate remains slightly below the Organization for Economic Co-operation and Development average. In addition, corporate downsizing and employer preferences for experienced workers have further limited labor market entry for younger individuals [49,50]. The post-pandemic surge in housing prices has also widened wealth disparities between homeowners and non-homeowners, disproportionately affecting individuals in their 20s and 30s and exacerbating economic insecurity [51]. Within this context, young adults with limited HL may lack the capacity to effectively respond to employment instability and economic shocks, which may partly explain their heightened risk of anxiety symptoms.
In middle-aged adults, HL was significantly associated with anxiety symptoms, whereas no significant relationship was observed between HL and HRQoL.
To date, few studies have examined age-specific associations between HL and anxiety symptoms. Middle adulthood is typically characterized by the accumulation of multiple life stressors, including workplace demands, family caregiving responsibilities, and emerging health problems, all of which have been significantly associated with declines in mental health and overall well-being [52,53]. In this context, these stressors may have exerted a stronger influence on HRQoL than HL among middle-aged adults in this study, which may partly explain why HL was associated with anxiety symptoms but not with HRQoL in this population.
Among older adults, no significant association was observed between HL and anxiety symptoms. This finding aligns with that of previous studies reporting no link between HL and anxiety symptoms in older populations [54]. The absence of a significant relationship may suggest that anxiety in older adults is more significantly influenced by factors such as declines in physical function, greater chronic disease burden, and social isolation than by HL [13]. Moreover, previous studies have demonstrated that older adults tend to underreport affective symptoms, including dysphoria and anhedonia, compared with younger adults [55], which may further attenuate the observed association between HL and anxiety symptoms in this age group. In contrast, a significant positive association was observed between HL and HRQoL among older adults. Similarly, a domestic study of older adults with mild cognitive impairment [17] reported a significant positive association between HL and HRQoL, suggesting that HL may be a key determinant of quality of life in this population.
Several mechanisms have been proposed in the literature to explain the associations among HL, anxiety symptoms, and HRQoL.
First, limited HL may directly contribute to increased anxiety symptoms and reduced HRQoL. Individuals with low HL may experience difficulty in understanding essential health information, which has been associated with greater psychological stress and anxiety [16]. Furthermore, HL is closely associated with effective self-management and the ability to cope with illness [56]. Consequently, limited HL may impair an individual’s capacity to manage their health, leading to poorer HRQoL [18].
Second, low HL may indirectly influence mental health and HRQoL by increasing the risk of chronic disease. Consistent with previous studies [57], we showed that individuals with low HL had a greater number of physician-diagnosed chronic conditions, particularly two or more conditions, and were more likely to experience anxiety symptoms and lower HRQoL. These findings suggest that low HL is associated with a higher chronic disease burden, which may partly explain its association with anxiety symptoms and HRQoL.
Third, HL has been associated with patterns of healthcare utilization and treatment adherence, which may contribute to delayed care and higher symptom burden.
In patients with hypertension, a community-based study reported that higher HL was significantly associated with better medication adherence [58], supporting the notion that improving HL may enhance adherence and timely care. In contrast, limited HL may hinder timely medical access and early intervention [11], potentially exacerbating the severity of anxiety symptoms. For example, despite the high prevalence of anxiety disorders, a recent population-based study in Singapore reported a median treatment delay of 9 years, with over half of individuals with anxiety disorders experiencing delayed treatment initiation [59].
Taken together, improving overall HL may help reduce delays in treatment and facilitate earlier interventions, which may, in turn, alleviate anxiety symptoms.
This study has several notable strengths. First, the use of nationally representative data from KNHANES addresses limitations of previous studies restricted to specific patient groups, older adults, or adolescents, thereby enhancing the generalizability of the findings.
Second, in this study, we provide a more comprehensive understanding of the relationship between HL, anxiety symptoms, and HRQoL by examining these outcomes simultaneously. Finally, age-stratified analyses identified differences in the associations of HL across the life course, providing essential evidence that HL may influence anxiety symptoms and HRQoL differently across age groups.
Study limitations
This study has certain limitations. First, although the analytical sample of approximately 5,000 participants ensured national representativeness, a significant number of participants were excluded due to missing covariate data. Excluding individuals with incomplete information may have introduced selection bias if excluded participants differed systematically from those included in the final analytical sample. Because the characteristics of excluded and included participants were not formally compared, the possibility of selection bias arising from a complete-case analysis cannot be fully excluded. In addition, the final sample size may not have been sufficient for detailed subgroup analyses, particularly in age-stratified models, potentially limiting the precision of estimates and statistical power within each age group.
Second, the cross-sectional design precludes causal inference. Significant associations were observed; however, they should not be interpreted as causal relationships. Reverse causation is also possible; for example, poorer mental health or lower HRQoL may limit an individual’s ability to access, understand, or apply health information. Moreover, as depression and perceived stress were not assessed in the 2023 KNHANES, adjustment for these key mental health variables was not feasible. The absence of these measures raises the potential for residual confounding.
Future longitudinal or interventional studies are needed to clarify the directionality and causal pathways of these associations.
Third, data were collected via self-reported questionnaires, which may have introduced recall and reporting biases. However, KNHANES employs trained interviewers who conduct face-to-face interviews, which likely mitigates some limitations of self-report data and enhances the reliability of responses.
Finally, we relied on data from a single survey year, limiting the ability to examine temporal changes or long-term trends. Future studies using multi-year or longitudinal data are crucial to address this limitation.
Conclusions
In this study, we examined the associations among HL, anxiety symptoms, and HRQoL in Korean adults. Lower HL was associated with significantly higher odds of anxiety symptoms and poorer HRQoL, with these associations most evident among young adults.
These findings suggest that HL may serve as an important social determinant of mental health and quality of life. Public health strategies to improve HL may help reduce anxiety symptoms and enhance HRQoL, particularly when interventions account for age-specific risk factors and apply tailored approaches.
Acknowledgments
Declaration of Generative AI and AI-assisted technologies in the writing process
Open ChatGPT was used by the authors to provide assistance when formulating limited portions of the manuscript and performing English language translation while preparing this work. The authors reviewed and edited all content, taking full responsibility for the published work.
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