Socioeconomic factors and the risk of cognitive decline among the elderly population in Japan.

AIM: In Japan, with the largest percentage of population aged 65 years or over, a dementia strategy is needed not only from a medical perspective, but also from a social policy viewpoint. This study aimed to verify the association between socioeconomic factors and cognitive decline among Japanese elderly people.
METHODS: Cognitive decline was assessed over a 15-year follow-up period using memory tests or through identifying missing/proxy responses to survey questions due to cognitive dysfunction. I analysed 1886 men and 2102 women in Japan, using competing risk models for cognitive decline, to consider survival effects. Survival effects have not been considered so far although those who live longer may be more likely to experience cognitive decline.
RESULTS: Men with higher income had a lower risk of cognitive decline (sub-hazard ratio [SHR]: 0.997, 95% confidence interval (CI): 0.995-0.999). Women with higher education had a lower risk of cognitive decline: 8 to 9 years (SHR: 0.646, 95% CI: 0.457-0.914) and ≥12 years (SHR: 0.360, 95% CI: 0.164-0.794) than women with 0 to 7 years of education.
CONCLUSION: This study suggests that cognitive decline among the elderly Japanese population is associated with socioeconomic factors, such as income and education, even after taking survival effects into account.