Age, Education, and Cognitive Decline: a prospective study of cognitive function in community-dwelling Chinese older adults in Hong Kong

Abstract

Background: This study aimed to investigate the changes in cognitive profiles and the effect of age and education on such changes in an older community cohort over a 5-year period. Methods: A random sample of 787 non-demented Chinese elders in Hong Kong was assessed with a comprehensive neuropsychological battery at baseline, in the 2nd and 5th year. Results: A total of 454 subjects were assessed at the 5th year. For subjects with normal cognitive function at baseline, 186 (56.9%) remained cognitively normal, 115 (35.2%) had mild cognitive impairment (MCI), and 26 (7.9%) became demented. For subjects with MCI at baseline, 28 (22%) reverted to normal, 59 (46.5%) remained as MCI, 40 (31.5%) became demented. The decline in scores of Cantonese Mini-Mental State Examination was significant over the years, with the rate of decline being greater after the 2nd year. Using logistic regression, age and education had significant predictive effects on the progression to dementia, but the protective effect of education was lost if the subjects were already suffering from MCI at the baseline. Age was a significant factor affecting the cognitive function over time, while the effect of education was lost in the baseline MCI subjects. Conclusions: A decline in cognitive profile took place before the clinical diagnosis of dementia. The protective effect of education on cognitive function appeared to have lost when the person started to have MCI.