Methods: The six waves (2006-2016) of Korean Longitudinal Study of Ageing (KLoSA) were used in this study. Our sample included N=2,198 individuals aged 65 and older, who were cognitively healthy (Korean Mini-Mental State Examination (K-MMSE) ≥ 24) at baseline (2006). The number of chronic conditions was counted out of 9 conditions including high blood pressure, diabetes, cancer, lung disease, heart problem, stroke, psychiatric problem, arthritis, and liver disease. Individuals were categorized into three groups: 1) no chronic condition (n=831), 2) one chronic condition (n=813), and 3) two or more chronic conditions (n=554). The K-MMSE was used to measure changes in cognitive function (i.e., memory, processing speed, orientation, language) over a 10-year period (range: 0-30). Baseline sociodemographic and health-related factors were included as covariates. Mixed effects model analyses were conducted using the SAS 9.4.
Results: Although on average, subjects experienced cognitive decline over a 10-year period, the rate of decline was significantly different across the three MCC groups (p <.001). Specifically, individuals with two or more chronic conditions showed greater cognitive decline compared to those with no or one chronic condition. Further, the results of the stratified analysis showed that different factors are associated with greater rates of cognitive decline within each MCC group. Among those with no chronic condition, being older, having lower income, lower education, and no functional limitation were associated with greater rate of cognitive decline. Among those with one chronic condition, being older, unmarried, not working, reporting poorer self-rated health, and having arthritis were associated with greater rate of cognitive decline. Among those with two chronic conditions, being older, having lower income, unmarried, and living alone were associated with greater rate of cognitive decline over a 10-year period.
Conclusions: Our findings indicate that individuals with MCC may experience greater rate of cognitive decline than those with no or one chronic condition among Korean older adults. Furthermore, the results indicate that risk factors that contribute to cognitive decline may differ across the three MCC groups. Thus, patient-centered self-management programs that specifically target those with and without MCC may be needed to mitigate cognitive decline among Korean older adults.