A longitudinal study of cognitive trajectories and its factors for Koreans aged 60 and over: A latent growth mixture model.

OBJECTIVE: The purpose of this study is twofold: first, to identify cognitive trajectories of older Koreans in a population-based longitudinal panel survey and, second, to investigate the main characteristics of the identified heterogeneous classes of cognitive trajectories.

METHODS: Data came from 2445 cognitively healthy persons aged 60 or older in the 2006 to 2012 Korean Longitudinal Study of Aging. Using Korean-mini mental status examination (K-MMSE) as a measure of global cognitive function, the latent growth mixture modeling approach examined potential heterogeneity of longitudinal changes over the 6 years.

RESULTS: This study found that older Koreans reported an average K-MMSE score of 27 at baseline and experienced a cognitive decline every 2 years by -1.6 (2006-2008) and -1.2 (2008-2010), followed by a slight increase of 0.7 in 2012. Results from the latent growth mixture modeling analysis indicated that there were 2 heterogeneous classes of longitudinal changes in the K-MMSE over a period of 6 years: class 1 with stable cognitive function and class 2 with sharp cognitive decline over time. The sharp decline was found among those older in age and with higher level of depression at baseline. On the contrary, being male, higher education, active social engagement, and regular exercise were main characteristics of stable cognitive function.

CONCLUSION: As the first to examine cognitive trajectories among older Koreans, this study highlighted heterogeneity of cognitive trajectories in the population that should be considered for developing differential intervention strategies aimed at both promoting healthy brain and delaying/preventing cognitive decline.