Serum Cholesterol Levels and Cognitive Function Assessed by P300 Latencies in an Older Population Living in the Community

To the Editor: The relationship between hypocholesterol-emia and depression or suicide in older people has focused on the hypothesis of serotonin metabolisim.1,2 Recently, not only the association with depression, but also an association with decline in cognitive function and low cholesterol levels have been reported.3 However, there is little evidence of the quanitative relationship between serum cholesterol level and cognitive function in older people. To address this important issue in a cross-sectional study, we related serum cholesterol level to the event-related auditory P300 potential, which was well known as a quantitative indicator of subtle cognitive function,4 in older people living in the community in Kahoku, Japan.5 Seventy-three apparently healthy older subjects aged 70 or older (70-91, mean age 79 years) were tested by a special auditory P300 oddball paradigm4 and were also examined for serum cholesterol level. Subjects with dementia or cerebrovascular diseases were excluded. The subject was presented with two different kinds of stimulation, 2000Hz (target) and 1000Hz (non-target), in a random sequence. The subject was to press the button in response to only the target stimulaion of 2000Hz. Electroencephalographic activity was recorded at the Cz, Pz sites and 20 to 30 waves were averaged to determine P300 latency. The longer the latency of P300 potential, the lower the cognitive function.4 Predictably, age was significantly correlated with P300 latencies (r = .405, P < .001) as well as with serum cholesterol levels (r = −0.419, P < .001). Notably, there was a weak but significantly inverse correlation between P300 latencies and serum choresterol concentrations, even after adjustment for the effects of age.(Figure 1). . Correlation between age-adjusted P300 latency and serum cholesterol concentration. Our cross-sectional data does suggest that lower serum cholesterol levels, even within normal range, were associated significantly with depressed cognitive functions. A prospective study is urgently needed to determine the relationship between serum cholestrerol level and cognitive function in the older population.