Hainsworth, Atticus H.

Background: Alzheimer’s disease (AD) and cerebrovascular pathology are the two most common causes of dementia, frequently co-occurring in older people. Community-based neuropathology studies indicate that vascular disease accounts for approximately one-third of the population-attributable risk of dementia, controlling for other pathologies (including AD). The proportion with vascular disease as co-pathology is likely to be higher (50–70%). The most common vascular substrate is cerebral small vessel disease, which includes small artery fibrosis (arteriolosclerosis), vascular amyloid deposits (cerebral amyloid angiopathy), and monogenic forms of small vessel disease, the commonest being Cerebral Autosomal Dominant Arteriopathy with Subcortical Infarcts and Leukoencephalopathy (CADASIL). Post-stroke cognitive impairment following both ischemic stroke and intracerebral hemorrhage also contributes. Aims and Methods: In this World Stroke Organization (WSO) scientific statement, we assembled a multi-disciplinary international group of experts to review the vascular contribution to dementia, encompassing both vascular and neurodegenerative dementia. This statement has been reviewed and approved by the WSO executive. Results: We summarize the epidemiology, neuropathology, cognitive profile, clinical impact and management of vascular disease in dementia and discuss the recent VasCog-2-WSO diagnostic criteria. We consider the substantial overlap with clinical stroke and with AD dementia. We catalog transcriptomic and proteomic studies that have revealed novel candidate molecules ( COL4A1/4A2, HTRA1, TRIM47, FOXF2 ) as possible treatment targets. We appraise imaging-based biomarkers relevant to vascular disease and potential biochemical markers (vascular endothelial growth factor-A, placental growth factor, interleukin-6, matrix metalloproteinase-9, cathepsin-B). We highlight the potential for vascular interventions to treat not only vascular dementia but also the vascular component of neurodegenerative dementia. We review recent clinical trials targeting multiple pathways, including nitric oxide signaling, high blood pressure, the GABAergic system, angiogenic activity, microglial inhibition, PDE3 and PDE5 inhibition, as well as dietary supplementation with omega-3 fatty acids, s-equol and vitamin E. Finally, we consider upcoming opportunities and challenges relevant to vascular disease in dementia. Conclusion: The vascular contribution to dementia is i) substantial, ii) increasingly understood at molecular and mechanistic levels, iii) a source of potential treatment opportunities. Data Access Statement: no original data are presented in this document.

Background: Cerebral small vessel disease (SVD) is common in older people and causes lacunar stroke and vascular cognitive impairment. Risk factors include old age, hypertension and variants in the genes COL4A1/COL4A2 encoding collagen alpha-1(IV) and alpha-2(IV), here termed collagen-IV, which are core components of the basement membrane. We tested the hypothesis that increased vascular collagen-IV associates with clinical hypertension and with SVD in older persons and with chronic hypertension in young and aged primates and genetically hypertensive rats. Methods: We quantified vascular collagen-IV immunolabeling in small arteries in a cohort of older persons with minimal Alzheimer pathology (N=52; 21F/31M, age 82.8±6.95 years). We also studied archive tissue from young (age range 6.2–8.3 years) and older (17.0–22.7 years) primates ( M mulatta ) and compared chronically hypertensive animals (18 months aortic stenosis) with normotensives. We also compared genetically hypertensive and normotensive rats (aged 10–12 months). Results: Collagen-IV immunolabeling in cerebral small arteries of older persons was negatively associated with radiological SVD severity (ρ: −0.427, P =0.005) but was not related to history of hypertension. General linear models confirmed the negative association of lower collagen-IV with radiological SVD ( P <0.017), including age as a covariate and either clinical hypertension ( P <0.030) or neuropathological SVD diagnosis ( P <0.022) as fixed factors. Reduced vascular collagen-IV was accompanied by accumulation of fibrillar collagens (types I and III) as indicated by immunogold electron microscopy. In young and aged primates, brain collagen-IV was elevated in older normotensive relative to young normotensive animals ( P =0.029) but was not associated with hypertension. Genetically hypertensive rats did not differ from normotensive rats in terms of arterial collagen-IV. Conclusions: Our cross-species data provide novel insight into sporadic SVD pathogenesis, supporting insufficient (rather than excessive) arterial collagen-IV in SVD, accompanied by matrix remodeling with elevated fibrillar collagen deposition. They also indicate that hypertension, a major risk factor for SVD, does not act by causing accumulation of brain vascular collagen-IV.

Abstract White matter hyperintensities (WMHs) are frequently seen on brain magnetic resonance imaging scans of older people. Usually interpreted clinically as a surrogate for cerebral small vessel disease, WMHs are associated with increased likelihood of cognitive impairment and dementia (including Alzheimer's disease [AD]). WMHs are also seen in cognitively healthy people. In this collaboration of academic, clinical, and pharmaceutical industry perspectives, we identify outstanding questions about WMHs and their relation to cognition, dementia, and AD. What molecular and cellular changes underlie WMHs? What are the neuropathological correlates of WMHs? To what extent are demyelination and inflammation present? Is it helpful to subdivide into periventricular and subcortical WMHs? What do WMHs signify in people diagnosed with AD? What are the risk factors for developing WMHs? What preventive and therapeutic strategies target WMHs? Answering these questions will improve prevention and treatment of WMHs and dementia.