ApoE levels in human CSF do not vary according to presence or absence of Alzheimer's disease, level of cognitive impairment, APOE genotype, gender or race, but do increase with age. A, Subjects were grouped by age and AD status. Subjects with a clinical dementia rating (CDR) score of 0 (cognitively normal) that were less than age 65 were placed into the first group (CDR 0, <65; n = 59). Subjects that were 65 and older with a CDR score of 0, 0.5, or 1–2 were placed into the second (CDR 0, n = 50), third (CDR 0.5, n = 21) and fourth (CDR 1+, n = 14) groups, respectively. There was no difference in CSF apoE levels by one-way ANOVA. B, Subjects were grouped by APOE genotype into four groups: E2/E3 (n = 23), E3/E3 (n = 72), E3/E4 (n = 52), and E4/E4 (n = 9). There was no difference in CSF apoE levels by one-way ANOVA. C, Subjects were divided into two groups, female (n = 109) and male (n = 57). There was no difference in CSF apoE levels by a two-tailed Student's T-test. D, Subjects were grouped by self-identified racial group: African American (n = 17) and Caucasian (n = 149). There was no difference in CSF apoE levels by a two-tailed Student's T-test. E, CSF apoE levels were graphed as a function of subject age (n = 168). The slope of the regression line was 0.05, with a 95% confidence interval of 0.02 to 0.08.