Association between recommended levels of physical activity and depressive symptoms among Japanese adults: A cross-sectional study

Background: Depression, a common mental illness, has a high global incidence. Regular physical activity at recommended levels is inversely associated with depression; however, this association has not yet been studied in the Japanese population. The present study examines the association between recommended physical activity criteria and depression, and depression score differences between physical activity groups and sociodemographic variables among Japanese adults. Methods: Sociodemographic data (gender, age, educational level, employment status, marital status, living conditions, and household income), the Japanese short version of the International Physical Activity Questionnaire (IPAQ), and the Center for Epidemiologic Studies Depression Scale were used to estimate the participants' physical activity and depression levels, respectively, via an Internet-based survey. A representative sample of 3000 Japanese adults answered the survey, stratified by gender and age. The present study followed current Japanese exercise guidelines to categorize respondents as "meeting" or "not meeting" the recommended criteria. Analysis of covariance, logistic regression, and two-way univariate analysis of covariance were performed. Results: Respondents not meeting the recommendations for physical activity had significantly higher depression scores than those meeting the recommendations. Individuals not meeting the recommended criteria had significantly higher depression scores than those meeting the criteria across the following variables: age, marital status, living conditions, and household income in men; and age, marital status, education level, employment status, and household income in women. Men who were unmarried and had low household income levels and women who were young, unmarried, and had lower household income levels had higher depression scores. Conclusion: The present study is one of the first studies to report on the cross-sectional associations among depression scores, physical activity levels, and various sociodemographic factors in the Japanese population.