To understand whether the decrease in the α-SMA fraction of the arterioles, small arteries, and medium-sized arteries in AD subjects (Fig. 2a) was related to CAA pathology and if the apparent lack of changes in the collagen fraction was due to the pooling of CAA+ and CAA− vessels (dilution effect), the three vessel types were analysed according to CAA status (CAA+ or CAA−) and antemortem cognitive status of the subjects (AD or NDCTRL) (Fig. 2c). Here, ACTA1 is linked to Alzheimer disease.