It is generally accepted that a chronic lack of blood flowto the deep brain area is common in, and may be related to the onsetof, AD and other dementias.115 A clinicaltrial (ClinicalTrials.gov Identifier: NCT02450253) has been initiatedto study the effects of tadalafil on patients with symptomatic smallvessel disease in the brain but lacking the vascular cognitive impairmentdiagnosis, which would contribute to the understanding of the roleof PDE5 inhibitors in contrasting the onset and progression of AD.3,115. This evidence concerns the gene PDE5A and Alzheimer disease.