Health literacy and physical and psychological wellbeing in Japanese adults

Abstract

Objective

To determine the prevalence of low health literacy and investigate the relationship between low health literacy and physical and psychological wellbeing in the Japanese general population.

Methods

A web-based cross-sectional survey was conducted in a national sample of Japanese adults. Health literacy was measured by self-report using the validated single-item screening question, “How confident are you filling out forms by yourself?” Wellbeing was measured with the physical and psychological domains of the World Health Organization Quality of Life Assessment-BREF. Effect sizes were computed by dividing the mean difference in scores by the standard deviation of the scores of all participants.

Results

In 1040 adult enrollees (mean age, 57-year-old; women, 52%), there were 161 (15.5%; 95% confidence interval [CI], 13.3–17.7%) with low health literacy. Individuals with low health literacy reported lower physical wellbeing (60.6 vs. 71.7, p < 0.001) and psychological wellbeing (59.7 vs. 68.3, p < 0.001) compared with those with adequate health literacy. After adjusting for sociodemographic characteristics, health risk behaviors and chronic conditions, these differences were still significant (physical wellbeing, p < 0.001; psychological wellbeing, p < 0.001). The effect sizes of the difference of scores were moderate for physical wellbeing (−0.55) and also for psychological wellbeing (−0.44).

Conclusion

The prevalence of self-reported low health literacy in Japanese adults is substantial and it is independently associated with poorer physical and mental wellbeing.

Practice implications

Efforts to monitor health literacy and to evaluate causal pathways to poor wellbeing should be encouraged in the Japanese population.

Introduction

There is a growing body of evidence supporting the impact of inadequate health literacy on the health of individuals [1]. Inadequate health literacy has been linked to lower use of preventive services [2], delayed care-seeking when symptomatic [3], poor understanding of one's medical condition [4], low adherence to medical instructions [5], poor self-care [6], higher healthcare costs [7] and increased mortality [8], [9]. In a recent report, 48% of U.S. adults lack the reading and numeracy skills to fully understand and act on health information [1]. Similarly, substantial portions of European populations have also been shown to have inadequate health literacy, despite the small number of publications related to the impact of inadequate health literacy in European countries [10].

To date, little research has been conducted on the prevalence of inadequate health literacy in other parts of the world, such as Asian countries including Japan. Japan in particular is well-known for having a high standard of educational attainment, including a high proportion that obtain university degrees [11]. Educational attainment, along with race/ethnicity and age, has been shown to be the leading demographic predictors of health literacy in the U.S. [12], [13]. Whereas 15% of U.S. adults do not have a high school diploma and 19% completed at least a 4-year university degree [14], only 8% of Japanese adults lack a high school diploma and fully 34% have completed at least a 4-year university degree [15]. Thus, there might be a lower prevalence of inadequate health literacy in Japan, although no research has been conducted to determine the prevalence of inadequate health literacy among Japanese adults.

English is a phonographic language in which phonemes, which do not intrinsically represent any particular meaning, are brought together to represent words. On the other hand, Japanese is a logographic language which uses a mixture of Chinese grapheme characters (Kanji) and two syllabary character systems (Hiragana and Katakana), to depict concepts, i.e., the images have intrinsic and somewhat flexible meaning. A phonographic script primarily represents words as units of sound. A logographic script primarily represents words as visual images [16]. Further, in Japanese, basic characters are often combined to communicate complex ideas. Consequently, most people can easily conceive the ideas close to the correct meaning of written words and sentences without prior knowledge.

Historically, the Japanese began adopting written language in the third century A.C.E. with Kanji through the Korean peninsula from China and then originally developed the Hiragana and Katakana in the ninth century. Currently, the Japanese Ministry of Education designates a list of 1006 Kanji (Kyoiku Kanji or Education Kanji) as the learning objective for all elementary school children. These and an additional 939 Kanji are designated as the learning objective for all junior high school students (Joyo Kanji or Ordinary Kanji). Logographic and syllabic characteristics of Japanese may be one cause of the high written literacy rate in Japan. In fact, 99.8% of junior high school graduates have mastered the Hiragana and Katakana [15], [17].

Due to the linguistic differences between English and Japanese, tools that have been developed in English language to directly measure health literacy cannot be simply translated. While simple, standardized assessment tools for readability and functional health literacy should be developed in Japanese, a recently developed surrogate measure for inadequate health literacy can be employed [18], [19], [20]. This one-item screening question was validated in recent studies as a measure of health literacy [18], [19], [20]; areas under the receiver operating characteristics curve for this single question were 0.84 based on the rapid estimate of adult literacy in medicine (REALM) [19] and 0.80 for the test of functional health literacy in adults (STOFHLA) [18]. Chew et al. have also shown that additional questions did not significantly increase the accuracy in detecting inadequate health literacy [19].

Despite accumulating evidence on health issues related to health literacy in the U.S. and European countries [6], [21], [22], a recent study indicated no association between health literacy and health status in ethnic minorities in the U.S. [23]. To determine the association between functional health literacy and physical and mental health status in Latinos and African Americans, Guerra et al conducted a cross-sectional study that used the STOFHLA and SF-12 in a sample of about 1300 Medicaid and/or Medicare Latino and African American adult patients at community clinics in Philadelphia and found that health literacy was not significantly associated with physical or mental health status thus questioning the generalizability to a sample of ethnic minorities of the perceived link between inadequate health literacy and poor health status [23]. Thus, research on the potential link between health literacy and health status is needed for people living outside the U.S. or Europe. Thus, the objective of this study was to estimate the prevalence of inadequate health literacy by examining self-reported low health literacy and to investigate the relationship between low health literacy and health status in the Japanese general population.