Health numeracy in Japan: measures of basic numeracy account for framing bias in a highly numerate population

Abstract

BackgroundHealth numeracy is an important factor in how well people make decisions based on medical risk information. However, in many countries, including Japan, numeracy studies have been limited.MethodsTo fill this gap, we evaluated health numeracy levels in a sample of Japanese adults by translating two well-known scales that objectively measure basic understanding of math and probability: the 3-item numeracy scale developed by Schwartz and colleagues (the Schwartz scale) and its expanded version, the 11-item numeracy scale developed by Lipkus and colleagues (the Lipkus scale).ResultsParticipants’ performances (n = 300) on the scales were much higher than in original studies conducted in the United States (80% average item-wise correct response rate for Schwartz-J, and 87% for Lipkus-J). This high performance resulted in a ceiling effect on the distributions of both scores, which made it difficult to apply parametric statistical analysis, and limited the interpretation of statistical results. Nevertheless, the data provided some evidence for the reliability and validity of these scales: The reliability of the Japanese versions (Schwartz-J and Lipkus-J) was comparable to the original in terms of their internal consistency (Cronbach’s α = 0.53 for Schwartz-J and 0.72 for Lipkus-J). Convergent validity was suggested by positive correlations with an existing Japanese health literacy measure (the Test for Ability to Interpret Medical Information developed by Takahashi and colleagues) that contains some items relevant to numeracy. Furthermore, as shown in the previous studies, health numeracy was still associated with framing bias with individuals whose Lipkus-J performance was below the median being significantly influenced by how probability was framed when they rated surgical risks. A significant association was also found using Schwartz-J, which consisted of only three items.ConclusionsDespite relatively high levels of health numeracy according to these scales, numeracy measures are still important determinants underlying susceptibility to framing bias. This suggests that it is important in Japan to identify individuals with low numeracy skills so that risk information can be presented in a way that enables them to correctly understand it. Further investigation is required on effective numeracy measures for such an intervention in Japan.

Associations of health literacy and information sources with health-risk anxiety and protective behaviors

“…Third, although it has been used and validated in previous studies, 15,25 our only measure of health literacy was a self-administered instrument. Skill-based measures of health literacy and numeracy such as the Newest Vital Sign 26 and the Lipkus scale 27 have recently been translated and validated in Japanese, and should be also used in future studies.…”

Improving Accuracy on Bayesian Inference Problems Using a Brief Tutorial

“…Despite initial reports, descriptive statistics for the Subjective Numeracy Scale (M = 4.19, SD = .85, Cronbach's α = .79), Abbreviated Numeracy Scale (M = 4.04, SD = 1.58, Cronbach's α = .54), and Graph Literacy Scale (M = 10.79, SD = 1.45, Cronbach's α = .40) revealed that two of the three scales did not reach minimum acceptable reliability for the sample used in this study. Nevertheless, previous studies have demonstrated relationships with the numeracy scale despite issues with internal consistency (e.g., Bruine de Bruin, McNair, Taylor, Summers, & Strough, 2014;Nelson, Reyna, Fagerlin, Lipkus, & Peters, 2008;Okamoto et al, 2012). Studies using the Graph Literacy Scale have predominantly reported only the reliability from the original study, so it is unclear whether internal consistency has been an issue in other studies.…”

The 14-item health literacy scale for Japanese adults (HLS-14)

“…The concept of HL has recently begun to attract notice in Japan, where nearly 100 % of the population over the age of 15 can read and write the Japanese language. There have been some attempts to develop self-rated scales for measuring HL in Japanese speakers [8][9][10][11][12]. One of these, developed by Ishikawa and colleagues [8], has the advantage of dealing with all three levels of HL: (1) functional literacy-sufficient basic skills in reading and writing to be able to function effectively in everyday situations, a definition which is broadly compatible with the narrow definition of HL; (2) communicative literacy-more advanced skills to participate actively in everyday activities, to extract information and derive meaning from different forms of communication, and to apply new information to changing circumstances; (3) critical literacy-more advanced skills to analyze information critically and to use this information to exert greater control over life events and situations [13].…”