Research Article: Education level and incident functional disability in elderly Japanese: The Ohsaki Cohort 2006 study

Date Published: March 12, 2019

Publisher: Public Library of Science

Author(s): Dieta Nurrika, Shu Zhang, Yasutake Tomata, Yumi Sugawara, Fumiya Tanji, Ichiro Tsuji, Alessandra Marengoni.


As the factors that link education level with incident functional disability in elderly Japanese have never been investigated, the present study investigated this issue in an elderly Japanese population. A 9-year prospective cohort study (2006–2015) was conducted among 8,680 Japanese individuals (≥65 years), Ohsaki city, Japan. In a baseline survey, we collected data on education level and potential mediators. Data on incident functional disability were retrieved from the Long-term Care Insurance database. The Cox proportional hazards model was used to estimate the hazard ratios (HRs) and 95% confidence intervals (CIs) for incident functional disability by education level (below upper-secondary education (reference), and upper secondary education and above). Mediating effects were estimated using accelerated failure time model and a logistic regression model. During 9-year follow-up period, 2,742 cases (31.6%) of incident functional disability were observed, and education level showed an inverse association with functional disability (P for trend <0.01). Participation in community activities had the largest mediating effect (34.7%) on the relationship between education level and incident functional disability. This effect remained among those aged 65–74 years (19.9%) but became negligible among those aged ≥75 years. Other potential mediators (such as smoking and drinking status) were also tested, but these showed only small mediating effects. The inverse association between education level and the incident risk of functional disability appears to be largely mediated by participation in community activities among elderly Japanese, especially those aged 65–74 years.

Partial Text

The proportion of elderly individuals in the population of Japan is projected to increase rapidly. In 2015, the number of people aged 65 years and over was approximately 26%, and by 2036 and 2065 it is estimated that this proportion will be 33% and no less than 38%, respectively [1]. The concept of healthy aging is therefore becoming crucial for elderly Japanese and for Japanese society as a whole, and disability prevention is one aspect of this issue [2].

In this cohort study, we found that education level was inversely associated with the risk of incident functional disability, in accord with previous studies [4–7, 9]. Furthermore, our results suggested that participation in community activities had a stronger effect on the above relationship than drinking and smoking status. To our knowledge, this is the first study to have evaluated mediating effects between education level and disability in a Japanese population aged 65 years and older.

In conclusion, the present study has shown that higher education level was significantly associated with a lower risk of incident functional disability, and that participation in community activities impacted moderately on the association between education level and incident functional disability, especially for those aged 65 to 74 years.




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