Rural–urban differences in the prevalence of cognitive impairment in independent community-dwelling elderly residents of Ojiya city, Niigata Prefecture, Japan

BACKGROUND: This study aimed to examine rural-urban differences in the prevalence of cognitive impairment in Japan. METHODS: We targeted 592 residents aged 65 years and older who did not use long-term care insurance services in one rural and two urban areas in Ojiya City, Japan. Of these, 537 (90.7 %) participated in the study. The revised Hasegawa's dementia scale (HDS-R) was used to assess cognitive function, and cognitive impairment was defined as a HDS-R score ≤20. Lifestyle information was obtained through interviews. The prevalence of cognitive impairment was compared according to the levels of predictor variables by odds ratios (ORs) calculated by a logistic regression analysis. RESULTS: Mean age of participants was 75.7 years (SD 7.0). The prevalence of cognitive impairment was 20/239 (8.4 %) in the rural area and 6/298 (2.0 %) in the urban areas, for a total of 26/537 (4.8 %) overall. Men tended to have a higher prevalence of cognitive impairment (P = 0.0628), and age was associated with cognitive impairment (P for trend <0.0001). The rural area had a significantly higher prevalence of cognitive impairment (age- and sex-adjusted OR = 4.04, 95 % CI: 1.54-10.62) than urban areas. This difference was significant after adjusting for other lifestyle factors. CONCLUSIONS: The prevalence of cognitive impairment was higher in the rural area relative to urban areas in Ojiya city. This regional difference suggests the existence of potentially modifiable factors other than lifestyle in relation to cognitive impairment.