Does poor dental health predict becoming homebound among older Japanese?

Background: Being homebound is an important risk factor of functional disability in older people. There is a possibility of bidirectional relationship between homeboundness and dental health. This prospective cohort study examined the association of dental health, which includes social function, on homeboundness in the future. Methods: The participants were >= 65 years, responded to two postal surveys conducted in 2006 and 2010, and were not homebound at baseline. Logistic regression analysis was used to estimate the odds ratios for homeboundness, defined as going out of one's home less than once weekly. Self-reported baseline dental status was used as the main predictor. Age, sex, marital status, educational attainment, income, comorbidity, depression, walking time, living alone, and area of residence were used as covariates. Results: Among 4390 non-homebound respondents, 7.4 % were homebound four years later. The proportions of homebound respondents with < 20 teeth without dentures, < 20 teeth with dentures, and >= 20 teeth were 9.7, 8.8, and 4.4 %, respectively. The odds for being homebound in the 65-74-year age group, adjusted for covariates, was 1.78 ( 95 % CI: 1.01-3.13; p < 0.05) times higher for respondents with < 20 teeth and no dentures than that for respondents with >= 20 teeth. Among the participants in the >= 75-year age group, a significant association of homeboundness and dental health was not observed. Conclusions: Among the young-old population, poor dental health predicted future onset of homeboundness, while depressive symptoms did not show any significant association.