Effects of Depression on Changes in Cognitive Function in Older Adults A Fixed-effects Model Analysis Using the Korean Longitudinal Study of Aging (KLoSA)

Purpose: This study identified the rate of change in cognitive function of community-based middle-aged and older adults and investigated the longitudinal effects of depression, health status, and health behavior by cognitive function group [normal, mild cognitive impairment (MCI), dementia] using data from the Korean Longitudinal Study of Aging. Methods: This longitudinal panel analysis collected 21,425 data points from 4285 participants. Cognitive function change patterns in the groups were examined through descriptive analysis. A fixed-effects model was estimated using demographic factors, such as depression, health behavior, and disease states as independent variables. Results: Compared with the baseline score of the mini-mental state examination (MMSE), the 8-year mean score decreased by 10.51, 8.6, and 1.21 for the dementia, MCI, and normal groups, respectively. The estimates for the normal group showed that an increase in the depression score significantly negatively impacted the MMSE score (B = -0.059, P < 0.001). However, compared with those of the MCI group (B = -0.044, P > 0.05), the estimates of the dementia group confirmed that depression significantly negatively affected cognitive function (B = -0.146, P < 0.05). Conclusion: Each group showed different patterns of cognitive decline. An annual follow-up cognitive impairment screening to investigate changes in MMSE score in community-based older individuals can enable early detection of dementia.