Association between health literacy and multimorbidity: a nationwide, cross-sectional study of a Japanese population

OBJECTIVES: To examine the relationship between health literacy and multimorbidity. DESIGN: Nationwide cross-sectional study. SETTING: Community settings across Japan. PARTICIPANTS: Community-dwelling participants aged 20 years or older were selected based on a quota sampling method that adjusted for age, sex and residential area. In total, 3678 participants from the Health Diary Study, with a mean age of 52.3 years (SD, 18.2 years; 1943 (52.8%) female participants), were included. PRIMARY OUTCOME MEASURE: Multimorbidity, the primary outcome measure, was defined as the presence of two or more chronic diseases. RESULTS: Of the 3678 participants, 824 (22.4%) had multimorbidity. The mean functional health literacy (FHL) and communicative and critical health literacy (CCHL) scores were 3.2 (SD, 0.7) and 3.6 (SD, 0.9), respectively. In the univariable analysis, both scores were associated with multimorbidity (p<0.001). However, in the multivariable modified Poisson regression analysis, only the FHL score was significantly associated with multimorbidity (per 1-point increase, 0.91; 95% CI 0.84 to 0.99). CONCLUSIONS: After adjusting for confounding variables, FHL, not CCHL, was significantly related to the presence of multimorbidity. Further longitudinal studies are required to examine the causal relationship between health literacy and multimorbidity.