Association Between Health Literacy and Understanding of Doctors' Explanations: The Yamagata Study
Study Design and Participants This study was cross-sectional in design, with questionnaires collected in 2021 from participants of the Yamagata Study. The Yamagata Study is a community-based prospective cohort study performed as part of a molecular epidemiological study that uses regional aspects of the Global Center of Excellence program in Japan . The study participants were Japanese residents of Yamagata Prefecture, Japan, living in seven municipalities (Yamagata, Sakata, Kaminoyama, Sagae, Higashine, Yonezawa, and Tendo) and age 40 to 74 years at the time of the baseline survey conducted from 2009 to 2015. Questionnaires for the present study were mailed to 17,527 participants of the Yamagata Study in 2021. A total of 12,216 people agreed to participate in our study by answering the questionnaires. Of these responses, 11,217 were included in the final statistical analysis. Data from 999 participants were excluded because of incomplete answers for questions on HL and understanding doctors' explanations. This study was approved by the ethics committee of Yamagata University School of Medicine (2022-119). Questionnaire Items The study participants in the 2021 survey were asked to self-report the following items as part of the questionnaire: age, gender, date of birth, current height and weight, lifestyle changes resulting from the COVID-19 outbreak (time at work, time spent on household chores, family care situation, household income, and amount of conversation and contact with family, friends, and acquaintances who do not live with the respondent), physical activity, current health status (including happiness and life satisfaction), levels of daily routine tasks (as measured by Activities of Daily Living), sleep habits, dental health, respiratory and gastric symptoms, smoking status, bladder and bowel habits, employment and household income, health service utilization (having a family doctor and taking prescribed medicine), HL, understanding of doctors' explanations, health information sources, and general views on health. The response data were linked to data collected in previous surveys. Previous research has clarified factors relating to HL and understanding doctors' explanations, including gender, age, family composition, socioeconomic status, and health status . A study from Japan reported that there was lower average HL among the Japanese public compared with the level in Europe, which could be due in part to an inefficient primary care system . Referring to these previous studies for the purposes of this analysis, we extracted data on HL, understanding doctors' explanations, basic characteristics (gender, age, family composition, living with family), work and income (employment type and household income), health (past medical history, health status, happiness), and health service utilization (having a family doctor and taking prescribed medicine). The 2021 survey lacked data relating to family composition, living with family, and past medical history; we therefore extracted this information from data collected in surveys between 2015 and 2020. We assessed the HL abilities of the study participants on an individual basis by using the Communicative and Critical Health Literacy (CCHL) scale, which consists of three communicative and two critical HL items . The three communicative HL statements that were presented to the participants for evaluation were “collect information regarding health through different sources,” “extract the intended information,” and “understand and communicate the acquired information.” The two critical HL items were “consider the credibility of the information” and “make decisions based on the information, particularly in the context of health-related issues.” Each item was scored on a five-point Likert scale (one point for strongly disagree and five points for strongly agree ). The scores of the two subscales were added together to provide a CCHL total score that ranged from 5 to 25. We assessed the main outcome variable, understanding doctors' explanations, by asking one question, “Do you understand the explanation you receive from your doctor when you visit a medical institution?” with the following five answer options: “understand well,” “understand,” “do not understand,” “not explained,” and “other.” “Understand well” and “understand” were recategorized as “adequate understanding,” and “do not understand” as “poor/inadequate understanding.” Response data for “not explained” ( n = 37) and “other” ( n = 28) were excluded from the analysis. Five options were provided for occupation. Those who answered any of the following items were recategorized as “employed”: “permanent employee,” “contract employee,” “temporary employee,” “part-time,” and “self-employed/manager.” Those who did not answer were categorized as “unemployed” because the questionnaire stated those who were unemployed (or were a housewife/house husband) were not required to respond. For annual household income, six options were regrouped into the following three categories for the purposes of the analysis: $1 = 147 yen (as of August 2024), 0–2.99 yen ($0–$20,340); 3–5.99 million yen ($20,480–$40,748); or more than 6 million yen (more than $40,816). (Those who answered “6–8.99 million yen ($40,816–$61,156),” “9–11.99 million yen ($61,224–$81,565),” “12–14.99 million yen ($81,663–$101,973),” and “more than 15 million yen” were all re-categorized as “more than 6 million yen (more than $40,816”). For past medical history, those who responded to past medical history were categorized as “having past medical history,” whereas those who did not answer were classified as having “no past medical history.” A questionnaire item about health status asked, “Please indicate how good or bad your health is today,” with a response scale of 0 (worst) to 100 (best). A further questionnaire item about happiness asked, “How happy are you feeling?” with a response scale of 1 ( unhappy ) to 5 ( very happy ). Data Analysis The respondents were divided into two groups based on their indicated understanding of their doctor's explanation and compared (chi-squared test or t-test) in terms of demographic characteristics, work and income, health, and health service utilization. Differences in the mean scores for HL level between the two groups were estimated using a t -test. In addition, the proportions for dichotomized HL level (divided by the median score of communicative and critical HL; “high level”: total HL ≥ 4; “low level”: total HL < 4) were compared between the two groups using the chi-squared test. The internal consistency of the five items was adequately high (Cronbach's alpha = 0.84). Factors showing a significant difference in univariable analysis were entered into multivariable analysis (logistic regression analysis) as covariates to estimate odds ratios (OR) and 95% confidence intervals (95% confidence interval [CI]) to identify the association between respondents' HL levels and understanding of doctors' explanations. Multicollinearity was assessed by using the variance inflation factor (VIF). The impact of multicollinearity was small because the VIF for the explanatory variables in all models was less than 4.0. Missing data were not included in each analysis. All statistical analyses were performed using SPSS statistical software (Version 28; IBM, Armonk, NY). For all analyses, a p value of .05 was used to determine statistical significance. 

This study was cross-sectional in design, with questionnaires collected in 2021 from participants of the Yamagata Study. The Yamagata Study is a community-based prospective cohort study performed as part of a molecular epidemiological study that uses regional aspects of the Global Center of Excellence program in Japan . The study participants were Japanese residents of Yamagata Prefecture, Japan, living in seven municipalities (Yamagata, Sakata, Kaminoyama, Sagae, Higashine, Yonezawa, and Tendo) and age 40 to 74 years at the time of the baseline survey conducted from 2009 to 2015. Questionnaires for the present study were mailed to 17,527 participants of the Yamagata Study in 2021. A total of 12,216 people agreed to participate in our study by answering the questionnaires. Of these responses, 11,217 were included in the final statistical analysis. Data from 999 participants were excluded because of incomplete answers for questions on HL and understanding doctors' explanations. This study was approved by the ethics committee of Yamagata University School of Medicine (2022-119). 

The study participants in the 2021 survey were asked to self-report the following items as part of the questionnaire: age, gender, date of birth, current height and weight, lifestyle changes resulting from the COVID-19 outbreak (time at work, time spent on household chores, family care situation, household income, and amount of conversation and contact with family, friends, and acquaintances who do not live with the respondent), physical activity, current health status (including happiness and life satisfaction), levels of daily routine tasks (as measured by Activities of Daily Living), sleep habits, dental health, respiratory and gastric symptoms, smoking status, bladder and bowel habits, employment and household income, health service utilization (having a family doctor and taking prescribed medicine), HL, understanding of doctors' explanations, health information sources, and general views on health. The response data were linked to data collected in previous surveys. Previous research has clarified factors relating to HL and understanding doctors' explanations, including gender, age, family composition, socioeconomic status, and health status . A study from Japan reported that there was lower average HL among the Japanese public compared with the level in Europe, which could be due in part to an inefficient primary care system . Referring to these previous studies for the purposes of this analysis, we extracted data on HL, understanding doctors' explanations, basic characteristics (gender, age, family composition, living with family), work and income (employment type and household income), health (past medical history, health status, happiness), and health service utilization (having a family doctor and taking prescribed medicine). The 2021 survey lacked data relating to family composition, living with family, and past medical history; we therefore extracted this information from data collected in surveys between 2015 and 2020. We assessed the HL abilities of the study participants on an individual basis by using the Communicative and Critical Health Literacy (CCHL) scale, which consists of three communicative and two critical HL items . The three communicative HL statements that were presented to the participants for evaluation were “collect information regarding health through different sources,” “extract the intended information,” and “understand and communicate the acquired information.” The two critical HL items were “consider the credibility of the information” and “make decisions based on the information, particularly in the context of health-related issues.” Each item was scored on a five-point Likert scale (one point for strongly disagree and five points for strongly agree ). The scores of the two subscales were added together to provide a CCHL total score that ranged from 5 to 25. We assessed the main outcome variable, understanding doctors' explanations, by asking one question, “Do you understand the explanation you receive from your doctor when you visit a medical institution?” with the following five answer options: “understand well,” “understand,” “do not understand,” “not explained,” and “other.” “Understand well” and “understand” were recategorized as “adequate understanding,” and “do not understand” as “poor/inadequate understanding.” Response data for “not explained” ( n = 37) and “other” ( n = 28) were excluded from the analysis. Five options were provided for occupation. Those who answered any of the following items were recategorized as “employed”: “permanent employee,” “contract employee,” “temporary employee,” “part-time,” and “self-employed/manager.” Those who did not answer were categorized as “unemployed” because the questionnaire stated those who were unemployed (or were a housewife/house husband) were not required to respond. For annual household income, six options were regrouped into the following three categories for the purposes of the analysis: $1 = 147 yen (as of August 2024), 0–2.99 yen ($0–$20,340); 3–5.99 million yen ($20,480–$40,748); or more than 6 million yen (more than $40,816). (Those who answered “6–8.99 million yen ($40,816–$61,156),” “9–11.99 million yen ($61,224–$81,565),” “12–14.99 million yen ($81,663–$101,973),” and “more than 15 million yen” were all re-categorized as “more than 6 million yen (more than $40,816”). For past medical history, those who responded to past medical history were categorized as “having past medical history,” whereas those who did not answer were classified as having “no past medical history.” A questionnaire item about health status asked, “Please indicate how good or bad your health is today,” with a response scale of 0 (worst) to 100 (best). A further questionnaire item about happiness asked, “How happy are you feeling?” with a response scale of 1 ( unhappy ) to 5 ( very happy ). 

The respondents were divided into two groups based on their indicated understanding of their doctor's explanation and compared (chi-squared test or t-test) in terms of demographic characteristics, work and income, health, and health service utilization. Differences in the mean scores for HL level between the two groups were estimated using a t -test. In addition, the proportions for dichotomized HL level (divided by the median score of communicative and critical HL; “high level”: total HL ≥ 4; “low level”: total HL < 4) were compared between the two groups using the chi-squared test. The internal consistency of the five items was adequately high (Cronbach's alpha = 0.84). Factors showing a significant difference in univariable analysis were entered into multivariable analysis (logistic regression analysis) as covariates to estimate odds ratios (OR) and 95% confidence intervals (95% confidence interval [CI]) to identify the association between respondents' HL levels and understanding of doctors' explanations. Multicollinearity was assessed by using the variance inflation factor (VIF). The impact of multicollinearity was small because the VIF for the explanatory variables in all models was less than 4.0. Missing data were not included in each analysis. All statistical analyses were performed using SPSS statistical software (Version 28; IBM, Armonk, NY). For all analyses, a p value of .05 was used to determine statistical significance. 

A total of 12,216 respondents agreed to participate in the current study (response rate = 69.7 %). The basic characteristics of the survey participants are listed in Table . We found that most participants self-reported as understanding their doctor's explanation adequately ( n = 10,967, 97.8%); only 2.2% of participants indicated poor understanding ( n = 250). Furthermore, significant differences in gender, age, family composition, living with family (child), household income, past medical history, health, happiness, and having a family doctor were observed between those with adequate understanding of and those with poor understanding of their doctor's explanation ( Table ). Table shows the HL levels among the two groups. Those indicating adequate understanding of their doctor's explanation showed significantly higher HL levels (total HL, communicative HL, and critical HL) than those with inadequate understanding. In addition, 40.7% of those in the group who declared adequate understanding of their doctor's explanation had low HL, compared with 80.4% in the group with inadequate understanding. The multivariable analysis results in Table show significant associations between HL and adequately understanding a doctor's explanation even after controlling for other items that were significant in the univariable analyses (adjusted OR [aOR] = 0.38, 95% CI 0.30–0.48). Additionally, the results revealed that men were less likely than women to adequately understand their doctor's explanation (aO R = 1.69, 95% CI 1.21–2.35), while people with higher levels of health and happiness were significantly more likely to adequately understand their doctor's explanation (health: aO R = 0.98, 95% CI 0.97–0.99; happiness: aO R = 0.76, 95% CI 0.61–0.96). Moreover, those who did not have a family doctor were more likely to have poor understanding of their doctor's explanation compared with those who did have a family doctor (aO R = 1.92, 95% CI 1.21–3.03). 

This study showed that lower HL was associated with a limited understanding of doctors' explanations, after adjusting for potential confounding. Those reporting an adequate understanding of their doctor's explanation accounted for 97.8% ( n = 10,967), whereas those declaring an inadequate understanding comprised only 2.2% ( n = 250). The results of the current study showed that the percentage of patients with low comprehension of the explanations given by their doctors was lower than in the Patient's Behavior Survey conducted in 2011 by the Ministry of Health, Labour and Welfare . In this prior study, 6.3% of inpatients and 3.4% of outpatients had low comprehension . In addition, the study participants' HL level (mean ± SD: 3.83 ± 0.57) was higher than the general population in a previous study (3.72 ± 0.68) . A possible reason for this is that the population of the current study is based on voluntary cohort study participants, so may include more health-conscious individuals than the general population. Health Literacy Level This study's main finding is that those with lower HL levels reported poorer understanding of their doctor's explanation than those with higher HL levels. This finding is consistent with existing evidence showing that many of the written materials relating to informed consent and complex spoken medical issues are too difficult for those with limited HL . For example, cancer patients with poor HL have a wide range of communication issues, both written and verbal, that may limit their understanding of cancer screening and symptoms, which could have a negative impact on their stage at diagnosis . These barriers also make it difficult for patients to fully understand the importance of giving informed consent for routine procedures and clinical trials, as well as to communicate and discuss the advantages and disadvantages of various treatment options . Thus, health care professionals need to ascertain their patients' and families' HL levels and explain concepts accordingly, in an easy-to-understand manner . Commonly recommended strategies are “universal precautions” (communicating in a clear and accessible way to all patients) and the “Teach-Back method” (confirming understanding by asking patients to explain in their own words what they are told). Family Doctors Our results showed that those who did not have a regular family doctor were less likely to adequately understand explanations from their doctors. In Japan, the primary care system is characterized by freedom of access to medical care, meaning that any patient can freely choose a medical institution to see a doctor without referral, and with no penalties or restrictions on switching to another doctor . In this context, according to the Public Opinion Survey conducted by the Cabinet Office , the most common reason given for not having a family doctor was “I have never thought about the necessity of a family doctor” (27.6%). Therefore, it is considered necessary to provide people with information on the importance of a family doctor and how to choose a suitable one. The same survey by the Cabinet Office  also asked what was important in choosing a family doctor and reported that the most common response was “a doctor who explains medical conditions and treatment details in an easy-to-understand manner” (60.3%). However, previous studies in Japan reported that there was a shortage of well-trained primary care physicians , and a lack of reliable health information on online platforms in Japan . Our previous study showed that people without a doctor whom they visit regularly were more likely to notice the improvement in health information when it was revised by trained professionals . Primary care physicians in Japan need to pay more attention to providing careful and clear explanations, especially for patients without a family doctor. Healthy People 2030, a national program in the United States that sets goals and objectives to improve people's health and well-being, addresses the importance of both personal and organizational HL . Organizational HL refers to how well individuals can find, understand, and apply resources to help them make decisions to improve their health. It is important to implement concerted hospital-wide efforts to create a better working environment for health care workers in which doctors, nurses, and other health care professionals can be more attentive to patients and their individual needs. Study Participants' Characteristics (Gender, Age, Health Status, and Happiness) In terms of gender, our results revealed that men were less likely to have adequate understanding of doctors' explanations compared with women. This is consistent with a previous study showing that women had higher functional HL (the capacity to read and comprehend health information) than men . It is also reported that female patients, compared with male patients, tended to have longer medical visits, communicating in more detail with health care providers , with consultations being conducted in a more patient-centered manner . Health care providers need to take into consideration such gender differences in communication and supporting decision-making. Turning to age, patient understanding was not shown to be associated with age group. This is inconsistent with known evidence indicating that limited HL is common among older people and that they tend to struggle with an array of communication issues such as poorer understanding of their medical conditions and treatments . Furthermore, compared with younger patients, older patients are typically likely to receive fewer opportunities to actively participate in their own care, even though it is crucial for doctors to inform and empower them to take responsibility for their health . In addition, older adults are likely to be left behind by digital health information . Interestingly, our study revealed that those with lower physical and mental health levels were less likely to adequately understand doctors' explanations. Although there is little literature reporting on the mechanism, a previous study reported that patients' cognition and behaviors such as decision-making, information processing, and interpersonal attitudes were significantly influenced by their emotions . Thus, patients may not be able to engage in communication with physicians when they are physically and emotionally unstable. Conversely, a systematic review reported that the abovementioned “Teach-Back method” could invite positive emotional changes in patients, such as improvements in happiness and health status . Health care professionals should use methods such as the Teach-Back method to promote a positive communication loop with their patients, and medical institutions should foster environments in which all patients, including not only Japanese nationals but also foreign nationals living in Japan, feel comfortable asking basic questions so that they feel enabled to make their own decisions on their treatments. Furthermore, community-based public health nurses, who typically have responsibility for coordinating with colleagues not only in the health, medical care, and welfare sectors but also in many other related organizations, need to support residents with limited HL to enable them to access a proper preventive health service. In addition, it is important to establish a system in which primary care physicians in Japan are responsible for the health care of patients and their family members to improve access to reliable health information for improved SDM . 

This study's main finding is that those with lower HL levels reported poorer understanding of their doctor's explanation than those with higher HL levels. This finding is consistent with existing evidence showing that many of the written materials relating to informed consent and complex spoken medical issues are too difficult for those with limited HL . For example, cancer patients with poor HL have a wide range of communication issues, both written and verbal, that may limit their understanding of cancer screening and symptoms, which could have a negative impact on their stage at diagnosis . These barriers also make it difficult for patients to fully understand the importance of giving informed consent for routine procedures and clinical trials, as well as to communicate and discuss the advantages and disadvantages of various treatment options . Thus, health care professionals need to ascertain their patients' and families' HL levels and explain concepts accordingly, in an easy-to-understand manner . Commonly recommended strategies are “universal precautions” (communicating in a clear and accessible way to all patients) and the “Teach-Back method” (confirming understanding by asking patients to explain in their own words what they are told). 

Our results showed that those who did not have a regular family doctor were less likely to adequately understand explanations from their doctors. In Japan, the primary care system is characterized by freedom of access to medical care, meaning that any patient can freely choose a medical institution to see a doctor without referral, and with no penalties or restrictions on switching to another doctor . In this context, according to the Public Opinion Survey conducted by the Cabinet Office , the most common reason given for not having a family doctor was “I have never thought about the necessity of a family doctor” (27.6%). Therefore, it is considered necessary to provide people with information on the importance of a family doctor and how to choose a suitable one. The same survey by the Cabinet Office  also asked what was important in choosing a family doctor and reported that the most common response was “a doctor who explains medical conditions and treatment details in an easy-to-understand manner” (60.3%). However, previous studies in Japan reported that there was a shortage of well-trained primary care physicians , and a lack of reliable health information on online platforms in Japan . Our previous study showed that people without a doctor whom they visit regularly were more likely to notice the improvement in health information when it was revised by trained professionals . Primary care physicians in Japan need to pay more attention to providing careful and clear explanations, especially for patients without a family doctor. Healthy People 2030, a national program in the United States that sets goals and objectives to improve people's health and well-being, addresses the importance of both personal and organizational HL . Organizational HL refers to how well individuals can find, understand, and apply resources to help them make decisions to improve their health. It is important to implement concerted hospital-wide efforts to create a better working environment for health care workers in which doctors, nurses, and other health care professionals can be more attentive to patients and their individual needs. 

In terms of gender, our results revealed that men were less likely to have adequate understanding of doctors' explanations compared with women. This is consistent with a previous study showing that women had higher functional HL (the capacity to read and comprehend health information) than men . It is also reported that female patients, compared with male patients, tended to have longer medical visits, communicating in more detail with health care providers , with consultations being conducted in a more patient-centered manner . Health care providers need to take into consideration such gender differences in communication and supporting decision-making. Turning to age, patient understanding was not shown to be associated with age group. This is inconsistent with known evidence indicating that limited HL is common among older people and that they tend to struggle with an array of communication issues such as poorer understanding of their medical conditions and treatments . Furthermore, compared with younger patients, older patients are typically likely to receive fewer opportunities to actively participate in their own care, even though it is crucial for doctors to inform and empower them to take responsibility for their health . In addition, older adults are likely to be left behind by digital health information . Interestingly, our study revealed that those with lower physical and mental health levels were less likely to adequately understand doctors' explanations. Although there is little literature reporting on the mechanism, a previous study reported that patients' cognition and behaviors such as decision-making, information processing, and interpersonal attitudes were significantly influenced by their emotions . Thus, patients may not be able to engage in communication with physicians when they are physically and emotionally unstable. Conversely, a systematic review reported that the abovementioned “Teach-Back method” could invite positive emotional changes in patients, such as improvements in happiness and health status . Health care professionals should use methods such as the Teach-Back method to promote a positive communication loop with their patients, and medical institutions should foster environments in which all patients, including not only Japanese nationals but also foreign nationals living in Japan, feel comfortable asking basic questions so that they feel enabled to make their own decisions on their treatments. Furthermore, community-based public health nurses, who typically have responsibility for coordinating with colleagues not only in the health, medical care, and welfare sectors but also in many other related organizations, need to support residents with limited HL to enable them to access a proper preventive health service. In addition, it is important to establish a system in which primary care physicians in Japan are responsible for the health care of patients and their family members to improve access to reliable health information for improved SDM . 

This study has some methodological limitations. First, this was a volunteer-based survey, thereby limiting the representativeness of the participants. We should therefore be cautious in generalizing the results to indicate a relatively high level of understanding of doctors' explanations, a relatively high HL level, and a lack of significant association of age with understanding. Second, data on some potential confounding factors, such as cohabiting family members and past medical history, were extracted from previously collected datasets, which might have changed by the time of the 2021 survey. Third, the level of understanding of doctors' explanations was self-reported, and the understandability of these explanations was not evaluated. Further detailed research applying an objective assessment of patients' understanding and confirming the understandability of the provided information is needed. Fourth, participants' HL was self-reported via the CCHL scale. Thus, further research is needed to evaluate HL using an objective test-based assessment of HL. 

The study results showed that those with lower HL are associated with poorer understanding of physicians' explanations. Factors associated with inadequate comprehension were being male, not having a family doctor, and having a lower level of health and happiness. Health care professionals need to communicate with patients in a way that considers their gender, HL level, and familiarity with seeing a family physician. 

