Impact of functional level on cognitive function in adults aged 45 and older than 45 years in the Korean Longitudinal...

This study aimed to analyse the potential factors affecting cognitive function, focusing on the functional level, by utilising longitudinal data from adults aged 45 years and older.

This was a secondary data analysis using data from the Korean Longitudinal Study of Aging (KLoSA) covering multiple waves of the survey. Cognitive function was measured using the Korean mini-mental state examination (K-MMSE), and activities of daily living (ADL), instrumental activities of daily living (IADL), diseases, hearing and visual impairments, and depression were included as independent variables. A fixed-effects model was used to assess the influence of independent variables on cognitive function over time.

Cognitive function, as measured using the K-MMSE, declined significantly, with the proportion of participants with normal cognition decreasing from 76% in the first wave to 68% in the eighth wave. Cognitive impairment and suspected dementia cases increased over time, and the average K-MMSE score dropped from 25.44 ± 5.31 to 24.71 ± 5.56. Panel regression analysis showed that impairments in ADL (b = -.44, p < .001) and IADL (b = -.64, p < .001), depression, and hearing and visual impairments were significantly associated with lower cognitive function. In addition, hypertension, cancer, heart disease, cerebrovascular accidents, psychiatric diseases and arthritis were significantly associated with cognitive decline. After adjusting for these factors, cognitive function still decreased significantly over time, explaining 75% of the variance in K-MMSE scores (R² = .75).

This study confirmed that IADL and ADL predict cognitive impairment, with IADL limitation significantly contributing to cognitive decline in the study participants. Evaluating IADL, ADL, and other chronic health conditions in adults aged 45 and older can help identify individuals at risk for cognitive impairment.