Temporal trends in cognitive function among community-dwelling older adults in Japan: Findings from the ILSA-J integrated cohort study.

BACKGROUND: As the population ages, it is important to consider whether older adults tend to have healthier lives. This study examined temporal trends in cognitive function among community-dwelling Japanese older adults. METHODS: The data source for this study was Integrated Longitudinal Studies on Aging in Japan (ILSA-J). We collected representative values for the Mini-Mental State Examination (MMSE) score obtained in 2010 and 2017; mean, standard deviation, and prevalence of ≤23 as cognitive impairment and ≥28 as intact cognitive function. Six cohorts (n=8,575) in 2010 and seven cohorts (n=6,089) in 2017 were included (age range 65-89). One-group meta-analyses were conducted to calculate pooled means of MMSE scores, the pooled prevalence of MMSE scores ≤23 and ≥28, and 95% confidence intervals (CIs). RESULTS: The mean MMSE score was higher in 2017 than in 2010 for all age groups in both men and women. The prevalence of MMSE ≤23 was lower in 2017 than in 2010 for all age groups for men and was lower in 2017 than in 2010 for all age groups other than for women aged 75-79 years. The prevalence of MMSE ≥28 was higher in 2017 than in 2010 for all age groups in both men and women. In addition, the pooled means of years of education was lower in 2010 than in 2017, which might be an explanatory factor. CONCLUSIONS: This study suggests that the cognitive function of community-dwelling Japanese older adults has improved in recent years. Future studies need to identify factors associated with the improvement.