Objective: to determine whether functional changes in the vasculature differ between Alzheimer's disease (AD) and vascular dementia (VAD).

Design: we determined vascular stiffness in patients with a clinical and radiological diagnosis of either AD or VAD and compared them to normal age- and sex-matched controls.

Methods: In all, 16 patients with late onset AD, 13 subjects with VAD and 16 age- and sex-matched controls were recruited to this study. Central arterial compliance (CAC), augmentation index (AI) and pulse wave velocity (PWV) (measures of arterial stiffness) were measured.

Results: the mean age was 77.7 ± 8.3 years (mean ± SD) in the AD group, 79.7 ± 8.9 years in the VAD group and 76.4 ± 6.9 in the controls (P = 0.44). CAC was significantly lower in subjects with VAD compared to both the AD and the control groups (0.57 ± 0.46 ml/mm Hg versus 1.12 ± 0.57 and 1.1 ± 0.47 ml/mm Hg respectively, P = 0.01). AI was significantly higher in the subjects with VAD compared to both the AD and the control groups (13.3 ± 9.0 versus 3.5 ± 11.4 and 4.2 ± 9.7% respectively, P = 0.03). PWV in the muscular and elastic arteries were not statistically different between the three groups but tended to be highest in the VAD group for carotid-radial measurements.

Conclusions: the reduced CAC and increased AI in VAD subjects indicate that the disease process is associated with less vascular compliance of the large elastic arteries in these patients, but not in patients with AD.