Angiotensin-converting enzyme measures and cerebrospinal fluid phosphorylated tau. Mean (standard error) in phosphorylated tau across tertiles of cerebrospinal fluid (CSF) angiotensin-converting enzyme (ACE) activity and CSF ACE protein level, in the control group (A) and the demented group (B). Analyses were adjusted for age and sex. Tertiles for CSF ACE activity: <121.66; 121.66 to 177.56; >177.56 relative fluorescence units. Tertiles for CSF ACE protein level: <2.95; 2.95 to 3.92; >3.92 ng/ml. **P < 0.01.