Longitudinal Association Between the Traditional Japanese Diet Score, Healthy Life Expectancy, and Life Expectancy: An International Ecological Study

Purpose: Cross-sectional analysis using open data has revealed an association between the traditional Japanese diet score (TJDS) and healthy life expectancy (HALE). This study aimed to clarify the association of the TJDS with the HALE and average life expectancy (LE) via a longitudinal analysis. Methods: Data regarding the food supply and total energy were extracted from the database of the Food and Agriculture Organization of the United Nations, and data regarding HALE and LE were obtained from the Global Burden of Disease Study 2019. The supply of items consumed frequently (rice, fish, soybeans, vegetables, and eggs) and less frequently (wheat, milk, and red meat) in the Japanese diet were scored (total: −8 to 8 points) and stratified into tertiles by country. The gross domestic product, aging rates, years of education, smoking rate, physical activity, and obesity rate were used as covariates. Longitudinal analyses were conducted for 143 countries, using the HALE and LE for each country from 2010 to 2019 as dependent variables and the 2010 TJDS as an independent variable. Results: The fixed effects (standard errors) were HALE 0.424 (0.102) and LE 0.521 (0.119), indicating significance (p < 0.001). Conclusion: The nine-year longitudinal analysis using international data suggests that the traditional Japanese diet based on rice may prolong the HALE and LE.