Vascular risk factors and Alzheimer's disease: are these risk factors for plaques and tangles or for concomitant vascular pathology that increases the likelihood of dementia? An evidence-based review

Table 1 Grading system for quality of evidence

Grade of evidence	Sampling	Design	Information
A1	Representative	Longitudinal prospective	Clinical and autopsy
A2	Non-representative	Longitudinal prospective	Clinical and autopsy
B1	Representative	Longitudinal prospective	Clinical only
B2	Non-representative	Longitudinal prospective	Clinical only
C1	Representative	Cross-sectional	Clinical and autopsy
C2	Non-representative	Cross-sectional	Clinical and autopsy
D1	Representative	Cross-sectional	Clinical only
D2	Non representative	Cross-sectional	Clinical only

ISSN: 1758-9193