Hemodynamic changes in Alzheimer's and Binswanger's diseases as evaluated by second-derivative finger photoplethysmography

Background:   Hemodynamics is often the focus of dementia research, but methodological difficulties have precluded such research. To clarify the role of hemodynamic factors in the pathogenesis of dementing illness, the newly developed, second-derivative finger photoplethysmography (SD-PTG), which can provide hemodynamic indices, was studied in 173 patients with dementia.
Methods:   The subject group consisted of 41 patients with Binswanger's disease (BD group), 31 patients with Alzheimer's disease with severe periventricular lucency (PVL; AD + PVL group), and 101 patients with Alzheimer's disease without PVL. The SD-PTG findings as well as the clinical findings of each group were compared with those of 114 controls without dementia. The heights of the a-, b-, c-, d-, and e-waves on SD-PTG waveforms were measured, and b/a and d/a ratios were used as indices of distensibility of the aorta and peripheral vascular impedance in the systemic circulation, respectively.
Results:   The b/a ratio was significantly higher in the BD and AD + PVL groups than in the AD − PVL group ( P  < 0.01). The d/a ratio was significantly lower in the BD group than in the AD + PVL, AD − PVL, and control groups ( P  < 0.01). The d/a ratio in the BD group correlated significantly with mini-mental state examination (MMSE) score ( r  = 0.47, P  = 0.0023).
Conclusions:   The results indicate that decreased distensibility of the aortic wall is associated with the white matter lesions in both types of dementia, while the low d/a ratio and the correlation between the d/a ratio and the MMSE score in the BD group indicate that increased peripheral impedance was associated with more extensive involvement of the white matter and cognitive decline in Binswanger's disease.