Lower Serum Cholesterol Level and Later Decline in Cognitive Function in Older People Living in the Community, Japan

To the Editor: We reported the inverse relationship between serum cholesterol level and cognitive function assessed by P300 latencies in the older population in a cross-sectional study.1 In addition, we also found a relationship between lower serum cholesterol level and later decline in cognitive function in older Japanese people in a longitudinal 3-year follow-up prospective study. The study population consisted of 93 nondemented healthy older subjects (mean age: 79.4 ± 3.4) living in the community. Each subject was administered the Mini-Mental State Examination (MMSE)2 and serum cholesterol concentration was measured as well both in 1991 and in 1994. In 1991, subjects were divided into two groups by serum cholesterol concentration; 33 subjects with serum cholesterol concentration greater than 200 mg/dL were defined as the high cholesterol group (HG group: mean age: 79.0 ± 3.3), and 60 subjects with serum cholesterol concentration of 200 mg/dL or less were defined as the lower cholesterol group (LC group: mean age: 79.7 ± 3.4). Mean serum cholesterol concentration in 1991 was 223.4 ± 18.2 mg/dL (range: 202–276 mg/dL) in the HC group and 166.2 ± 22.3 mg/dL (range: 107–196 mg/dL) in the LC group, respectively. Figure 1 compares the changes in MMSE scores between the two groups from 1991 to 1994. Predictably, MMSE scores decreased significantly during the 3-year period, both in the HC group (from 29.2 ± .8 to 28.6 ± 1.6, P = .039) and in the LC group (from 29.2 ± .8 to 27.6 ± 2.2, P < .001) by paired t test. There were no significant differences either in mean age or in MMSE scores in 1991 between the two groups. Notably, statistical analysis using ANOVA with repeated measures, which was used to evaluate the effects of group assignment on change over time, revealed that declines in MMSE scores were small but significant, and more declined in the LC group than in the HC group (P = .0178). . Comparison of decline in MMSE scores between higher and lower cholesterol (T-Cho) groups during a 3-year period. P, by ANOVA with repeated measures (interaction between group and time). Although levels of hypercholesterolemia in Japanese people are lower than those found in Western populations,3 these longitudinal data suggest that lower serum cholesterol level may be related to a later decline in cognitive function, at least in the older Japanese population.