Vascular Dementia

Abstract

Vascular dementia is a form of dementia caused by cerebrovascular disease — the damage that strokes, small-vessel disease, and chronic poor blood supply inflict on the brain. It belongs to cognitive psychology because its toll is chiefly cognitive: unlike the memory-first decline of Alzheimer's disease, its earliest and most disabling losses fall on executive function and processing speed, the frontal-subcortical control processes that vascular injury strikes first. It is the second most common cause of dementia after Alzheimer's disease, and the two frequently co-occur as mixed dementia. What makes vascular dementia distinctive is that its cause is, in principle, preventable: the same risk factors that drive heart disease and stroke — hypertension above all — drive it, and modern practice frames it within the broader spectrum of vascular cognitive impairment.

Keywords: vascular dementia, cerebrovascular disease, small-vessel disease, executive function

Vascular dementia (VaD) is the cognitive decline that follows damage to the brain's blood supply — the loss of thinking, memory, and self-control that results when strokes or the slow strangulation of small vessels destroy enough brain tissue to disable the mind (O'Brien & Thomas, 2015). It has been recognised for over a century, but its modern study begins with the demonstration that dementia in old age is often *vascular* rather than purely degenerative, and with a bedside tool for separating the two (Hachinski et al., 1975). What makes vascular dementia a subject for cognitive psychology, rather than vascular medicine alone, is the *shape* of the deficit it produces: a slowing of thought and a failure of planning and control that reflects where cerebrovascular disease does its damage — in the frontal lobes and the deep white matter that connect them (Iadecola, 2013). The clinical problem of vascular dementia is, in the end, a cognitive one.

What Vascular Dementia Is

Vascular dementia is dementia — an acquired, persistent decline in cognition severe enough to impair daily life — that is *caused* by disease of the brain's blood vessels (O'Brien & Thomas, 2015). The category is defined by its cause rather than its symptoms, and this is what sets it apart from Alzheimer's disease, which is defined by its molecular pathology. Any vascular process that destroys or disables enough brain tissue can produce it: a single large stroke in a critical location, a series of smaller strokes, the slow accumulation of damage in the deep white matter from diseased small arteries, or bleeding into the brain. The unifying idea is that the cognitive loss is *downstream of the vasculature* — prevent the vascular disease and, in principle, the dementia is prevented with it (Gorelick et al., 2011).

That vascular disease is a major cause of dementia is not a modern discovery. The systematic study of the brains of demented older people showed decades ago that softening from infarcts contributed substantially to dementia in old age, alongside the plaques and tangles of Alzheimer's disease, and that the two often appeared together (Tomlinson et al., 1970). The modern clinical concept took shape when Hachinski and colleagues argued that a *multi-infarct* process — the cumulative effect of many small strokes — was a distinct and identifiable cause of dementia, and offered a bedside score to separate it from primary degeneration (Hachinski et al., 1975). Formal diagnostic criteria followed, most influentially the NINDS-AIREN research criteria, which required both a dementia syndrome and evidence of cerebrovascular disease, together with a plausible temporal or anatomical link between them (Roman et al., 1993).

Contemporary thinking has broadened the frame. Rather than treating vascular dementia as a single endpoint, researchers now speak of *vascular cognitive impairment* — a spectrum running from mild, isolated deficits to full dementia, of which vascular dementia is the severe end (Sachdev et al., 2014), (van der Flier et al., 2018). This shift matters because it directs attention to the *early*, still-treatable stages, when the damage is limited and the risk factors that drive it can still be controlled.

Types of Vascular Dementia

Vascular dementia is not a single disease but a family of conditions that share a vascular cause while differing in the *kind* and *location* of the damage. In the international MeSH vocabulary, the descriptor Dementia, Vascular sits beneath the broader categories of cerebrovascular disorders and of dementia, and it names two more specific forms as its subtypes. Because the categories are indexing conventions rather than mutually exclusive boxes, a single patient can fall under more than one, and mixed pictures are the rule rather than the exception (Table 1).

The two subtypes MeSH files directly under vascular dementia are CADASIL and multi-infarct dementia. *CADASIL* — cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy — is the archetypal *hereditary* small-vessel disease, caused by mutations in the *NOTCH3* gene, and it serves as a monogenic model of how small-vessel pathology produces vascular cognitive impairment (Joutel et al., 1996). *Multi-infarct dementia* is the classic form Hachinski described: dementia produced by the cumulative loss of tissue to multiple discrete strokes, typically from large- or medium-vessel disease (Hachinski et al., 1975). Beyond these two indexed subtypes, clinicians routinely distinguish *post-stroke dementia*, which follows a single strategically-placed or large infarct (Kalaria et al., 2016); *subcortical ischaemic vascular dementia*, driven by diffuse small-vessel disease of the deep white matter and now regarded as the most common form (Pantoni, 2010); and *mixed dementia*, in which vascular and Alzheimer pathology coexist and compound one another (Schneider et al., 2007).

Table 1

The Principal Forms of Vascular Dementia

Note. MeSH classifies CADASIL and multi-infarct dementia directly under Dementia, Vascular; the post-stroke, subcortical, and mixed forms are standard clinical distinctions (O'Brien & Thomas, 2015), (van der Flier et al., 2018). MeSH is an indexing classification, not a claim that these forms are mutually exclusive — in practice they overlap, and mixed pathology is the norm in older patients (Schneider et al., 2007).

How Cerebrovascular Disease Becomes Cognitive Decline

The brain is metabolically greedy and holds almost no energy reserve, so it depends on a continuous, finely-regulated blood supply delivered through a partnership of neurons, glia, and blood vessels known as the *neurovascular unit* (Iadecola, 2013). Cerebrovascular disease attacks this partnership along two broad routes. The first is *large-vessel* disease: a clot or a burst artery deprives a territory of the cortex of blood, killing a wedge of tissue in minutes. When enough such infarcts accumulate, or one falls in a critical hub, the result is dementia (Kalaria et al., 2016). The second, and now considered the more common, is *small-vessel* disease: the tiny penetrating arteries that feed the deep white matter thicken and stiffen with age and hypertension, so the deep tissue is chronically underperfused. This produces the two hallmark lesions of small-vessel disease — *lacunes*, tiny cavities left where a small vessel has occluded, and *white-matter hyperintensities*, diffuse regions of damage visible on magnetic-resonance imaging (Pantoni, 2010), (Wardlaw et al., 2013).

The consequence of small-vessel disease for cognition follows directly from *where* it does its damage. The deep white matter is the wiring that connects the frontal lobes to the rest of the brain; damaging it disconnects the frontal control system from the networks it must coordinate (Debette & Markus, 2010). This is why the burden of white-matter hyperintensities on a brain scan predicts cognitive decline, and why the profile of small-vessel dementia is dominated by slowed processing speed and failing executive function rather than by the amnesia of Alzheimer's disease. Even *silent* infarcts — small strokes that produce no obvious symptom at the time — more than double the risk of later dementia, because each one subtracts a little more from the brain's functional reserve (Vermeer et al., 2003).

The two routes rarely travel alone, and they rarely travel without Alzheimer's disease. Autopsy studies of community-dwelling older people show that *mixed* pathology — vascular lesions together with Alzheimer plaques and tangles — accounts for most dementia, and that the two kinds of damage act additively, each lowering the threshold at which the other produces symptoms (Schneider et al., 2007). Vascular disease, in other words, is often the factor that tips a brain already burdened with Alzheimer pathology over the edge into clinical dementia.

The Cognitive Cost of Vascular Damage

The cognitive syndrome of vascular dementia has a recognisable shape that distinguishes it, at least early on, from Alzheimer's disease. Where Alzheimer's disease begins with a failure of episodic long-term memory — the inability to lay down new memories — vascular dementia, especially its common subcortical form, begins with a *dysexecutive* and *slowed* profile: difficulty planning, organising, and switching between tasks, sustained mental slowness, and impaired attention, with memory relatively spared until later (O'Brien & Thomas, 2015). The failure of working memory and the slowing of processing speed are the everyday face of the disconnection that white-matter disease produces (Iadecola, 2013).

The *course* of the decline is a second distinguishing feature. Classic multi-infarct dementia declines in a *stepwise* fashion: a period of stability, then an abrupt drop coinciding with a new stroke, then stability again at the lower level — a staircase, in contrast to the smooth downward slope of Alzheimer's disease (Hachinski et al., 1975). This stepwise trajectory was one of the features the Hachinski Ischemic Score used to identify a vascular cause at the bedside. The pattern is clearest in the multi-infarct form; subcortical small-vessel dementia, by contrast, can decline gradually and be hard to distinguish from Alzheimer's disease on course alone, which is one reason imaging has become central to diagnosis (Wardlaw et al., 2013).

The distinctiveness of the vascular profile should not be overstated. Because vascular and Alzheimer pathology so often coexist, and because a strategic infarct in the memory circuitry can produce an amnestic picture, the clinical profiles blur in practice. The value of understanding the *typical* vascular signature — early executive dysfunction, slowed speed, stepwise course, memory relatively preserved — is that it raises the possibility of a vascular contribution, which then prompts the search for the risk factors that can be treated (Gorelick et al., 2011).

Worked Example

The oldest quantitative tool in this field is the *Hachinski Ischemic Score*, a bedside checklist that weights clinical features thought to point toward a vascular rather than a degenerative cause of dementia (Hachinski et al., 1975). Each feature that is present contributes its assigned weight, and the total is a single number that places a patient on a spectrum from the degenerative to the vascular. Formally, if $x_i \in \{0,1\}$ indicates whether feature $i$ is present and $w_i$ is its weight, the score is a simple weighted sum:

$$S = \sum_{i} w_i \, x_i$$

The heavily-weighted features (worth 2 points each) are the ones most specific to a vascular cause: *abrupt onset*, a *stepwise* course, a *history of strokes*, and *focal neurological symptoms and signs*. Lighter features (1 point) include fluctuating course, nocturnal confusion, hypertension, and emotional lability. Consider a patient whose dementia began *abruptly* $(w=2)$, has progressed in a *stepwise* fashion $(w=1)$, who has a *history of strokes* $(w=2)$, a *history of hypertension* $(w=1)$, and *focal neurological signs* on examination $(w=2)$. Their score is:

$$S = 2 + 1 + 2 + 1 + 2 = 8$$

The interpretation rests on two thresholds Hachinski and colleagues identified: a score of 7 or more points toward a multi-infarct (vascular) cause, a score of 4 or less toward primary degeneration such as Alzheimer's disease, and the narrow band of 5–6 is indeterminate, often reflecting mixed disease. Our patient's score of 8 therefore falls in the vascular range:

$$S = 8 \geq 7 \;\Rightarrow\; \text{vascular (multi-infarct) pattern}$$

The worked figure repays careful reading, because it also marks the limits of the tool. The Hachinski score is a *heuristic*, not a diagnosis: it captures the classic multi-infarct picture well but performs poorly against the *subcortical small-vessel* form, which lacks the abrupt onset and focal signs the score rewards, and it cannot detect the *mixed* disease that is in fact most common (Schneider et al., 2007). A high score raises the probability of a vascular contribution; it does not settle it, and modern diagnosis adds neuroimaging to confirm that cerebrovascular lesions are present and sufficient to explain the deficit (Roman et al., 1993), (Wardlaw et al., 2013). The arithmetic of the score is clean; the biology it points at is not.

Discussion

The scientific interest of vascular dementia for cognitive psychology is that it is, in effect, a natural experiment in *disconnection*. Where a neurodegenerative disease dissolves specific cell populations, cerebrovascular disease severs the connections between regions — and by doing so it reveals how much of higher cognition depends not on any single area but on the *communication* between the frontal lobes and the rest of the brain (Iadecola, 2013). The reliable early loss of executive control and processing speed in subcortical vascular dementia is the predictable signature of white-matter damage that isolates the frontal control system, and it teaches the same lesson as any disconnection syndrome: that the distinctly human capacities for planning and self-regulation are the most fragile, because they depend on the most far-flung and vulnerable wiring (Debette & Markus, 2010).

The three demonstrations on this page track that idea at three resolutions. The small-vessel display shows how lacunes and white-matter change accumulate in the deep brain and disconnect the frontal system; the stepwise-decline display shows how the multi-infarct course descends in a staircase distinct from the smooth slope of Alzheimer's disease; and the Hachinski-score display shows how clinical features were once weighted to separate the two at the bedside. Where the account remains genuinely open is at the *boundary between vascular and degenerative disease*. Because the two pathologies so often coexist and compound, attributing a given patient's dementia cleanly to a vascular or an Alzheimer cause is frequently impossible, and the field has moved toward describing the *mixture* and the *contribution* of each rather than forcing a single label (Sachdev et al., 2014), (Skrobot et al., 2018). The harder scientific questions — how much vascular damage is enough, why identical lesions produce dementia in one person and not another, and how to measure the vascular contribution in life — remain unresolved.

Cognitive Implications

The clearest and most consequential implication of vascular dementia is that a large share of cognitive decline in old age is, in principle, *preventable*. The vascular risk factors that damage the heart and cause strokes — hypertension above all, together with diabetes, smoking, and atrial fibrillation — are the same factors that drive vascular cognitive impairment, and midlife hypertension in particular predicts cognitive decline decades later (Gottesman et al., 2014). This reframes a portion of dementia not as an inevitable consequence of ageing but as the late cognitive cost of treatable vascular disease, and it places vascular dementia at the centre of the wider public-health case that a substantial fraction of dementia could be delayed or prevented by acting on modifiable risk (Livingston et al., 2020).

A second implication concerns cognitive reserve and the *threshold* at which damage becomes dementia. Because vascular and Alzheimer pathology act additively, and because reserve raises the burden of pathology a brain can absorb before symptoms appear, the same vascular lesion may be silent in one person and disabling in another. This makes vascular disease a powerful *modifier* of when other pathologies declare themselves, and it means that reducing vascular injury can buy cognitive time even when a co-existing degenerative process cannot be stopped (Schneider et al., 2007). For cognitive assessment, the practical lesson is that a dysexecutive, slowed profile with a vascular risk history should prompt a search for treatable cerebrovascular contributors, because unlike most causes of dementia, the vascular ones can be acted upon (Gorelick et al., 2011).

Current Directions

Three fronts are active. The first is *prevention through vascular control*. The strongest recent evidence that treating vascular risk protects cognition came from the SPRINT MIND trial, in which intensively lowering blood pressure reduced the combined risk of mild cognitive impairment and dementia — the first large randomised demonstration that a vascular intervention can bend the cognitive curve, though the effect on dementia alone did not reach significance (SPRINT MIND Investigators, 2019). This has made rigorous risk-factor control the central practical strategy for vascular cognitive impairment (Livingston et al., 2020).

The second front is *standardising diagnosis and imaging*. Because small-vessel disease is defined largely by what is seen on a brain scan, the field agreed common neuroimaging standards — the STRIVE criteria — so that lacunes, white-matter hyperintensities, and related markers are described the same way across studies (Wardlaw et al., 2013), and consensus efforts such as VICCCS have worked to harmonise the diagnostic categories of vascular cognitive impairment themselves (Skrobot et al., 2018). The third front is *mechanism and treatment*. No drug is approved specifically for vascular dementia; cholinesterase inhibitors borrowed from Alzheimer's disease give at best modest benefit (Erkinjuntti et al., 2002), so understanding the biology of the neurovascular unit and small-vessel disease — how chronic hypoperfusion and a failing blood–brain barrier injure the white matter — is the priority for finding targets that do not yet exist (Iadecola, 2013), (van der Flier et al., 2018).

Common Misconceptions

Vascular dementia is caused only by noticeable strokes.

No. While large, obvious strokes can cause it, the most common form is driven by small-vessel disease and by silent infarcts that produce no symptom at the time. The gradual, diffuse damage to the deep white matter can accumulate into dementia without a single dramatic event (Pantoni, 2010), (Vermeer et al., 2003).

Vascular dementia always begins suddenly and declines in steps.

Only the multi-infarct form typically does. Subcortical small-vessel dementia often begins insidiously and declines gradually, closely resembling Alzheimer's disease on course alone. The classic stepwise picture is one presentation among several, not a defining feature of all vascular dementia (O'Brien & Thomas, 2015).

A dementia is either vascular or Alzheimer's, not both.

In older people, mixed disease is the rule. Autopsy studies show that most dementia reflects a combination of vascular and Alzheimer pathology acting together, each lowering the threshold at which the other produces symptoms. Forcing a single label misrepresents what is usually a blend (Schneider et al., 2007).

Nothing can be done about vascular dementia.

Unlike most causes of dementia, its principal risk factors are treatable. Controlling blood pressure and other vascular risks lowers the risk of cognitive decline, and the SPRINT MIND trial provided randomised evidence that intensive blood-pressure control reduces the risk of cognitive impairment (SPRINT MIND Investigators, 2019), (Gorelick et al., 2011).

Glossary

Attention.

The selection and sustaining of mental focus; commonly impaired early in vascular dementia as white-matter disease disconnects frontal control networks.

CADASIL.

Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy; a hereditary small-vessel disease caused by NOTCH3 mutations and a monogenic model of vascular dementia.

Cerebral small-vessel disease.

Disease of the brain's smallest penetrating arteries, producing lacunes and white-matter damage in the deep tissue; the most common substrate of vascular dementia.

Cognitive reserve.

The brain's capacity to absorb pathology before symptoms appear; it raises the threshold at which vascular and other damage produces clinical dementia.

Executive function.

The set of frontal control processes — planning, inhibition, and flexible switching — whose early failure is the cognitive signature of subcortical vascular dementia.

Hachinski Ischemic Score.

A weighted bedside checklist of clinical features used to distinguish a multi-infarct (vascular) cause of dementia from a primary degenerative one; a heuristic, not a diagnosis.

Lacune.

A tiny cavity in the deep brain left where a small penetrating artery has occluded; a hallmark lesion of small-vessel disease.

Long-term memory.

The durable store of knowledge and experience; relatively preserved early in vascular dementia, in contrast to the memory-first decline of Alzheimer's disease.

Mixed dementia.

Dementia in which vascular lesions and Alzheimer pathology coexist and compound one another; the most common picture in older people.

Multi-infarct dementia.

Dementia produced by the cumulative loss of tissue to multiple discrete strokes; the classic form first described by Hachinski and colleagues.

Neurovascular unit.

The functional partnership of neurons, glia, and blood vessels that matches blood flow to neural activity; its failure underlies the vascular contribution to cognitive decline.

Post-stroke dementia.

Dementia that follows a single large or strategically-placed infarct, with an onset that can be dated to the stroke.

Processing speed.

The rate at which the brain takes in and acts on information; its slowing is a core, early feature of subcortical vascular dementia.

Subcortical ischaemic vascular dementia.

The form driven by diffuse small-vessel disease of the deep white matter, dominated by slowed processing and executive dysfunction; now regarded as the most common form.

Vascular cognitive impairment.

The full spectrum of cognitive loss caused by cerebrovascular disease, from mild deficits to dementia; vascular dementia is its severe end.

Vascular dementia.

An acquired, persistent cognitive decline severe enough to impair daily life that is caused by disease of the brain's blood vessels.

White-matter hyperintensity.

A region of diffuse damage in the deep white matter seen as a bright signal on magnetic-resonance imaging; its burden predicts cognitive decline.

Working memory.

The system that holds and manipulates information over seconds; its failure contributes to the dysexecutive profile of vascular dementia.

Key Researchers

Vladimir Hachinski

Neurologist at Western University who introduced the concept of multi-infarct dementia and, with colleagues, the Ischemic Score that first separated a vascular from a degenerative cause of dementia at the bedside, and who later championed the broader construct of vascular cognitive impairment. Wikipedia

Costantino Iadecola

Neuroscientist at Weill Cornell Medicine whose work defined the neurovascular unit and the pathobiology linking cerebral blood-flow regulation, small-vessel disease, and cognitive impairment. ORCID

Anne Joutel

Geneticist at INSERM who identified NOTCH3 mutations as the cause of CADASIL, the archetypal hereditary small-vessel disease and a monogenic model of vascular dementia. ORCID

Raj N. Kalaria

Neuropathologist at Newcastle University who characterised how stroke injury and small-vessel pathology produce cognitive impairment and vascular dementia, and a leader of the post-stroke dementia cohorts. ORCID

John T. O'Brien

Old-age psychiatrist at the University of Cambridge and co-author of the Lancet Seminar on vascular dementia, working on the imaging and clinical boundaries of vascular and mixed dementia. ORCID

Joanna M. Wardlaw

Neuroradiologist at the University of Edinburgh who led the STRIVE consensus on neuroimaging standards for small-vessel disease, the imaging substrate of most vascular cognitive impairment. ORCID

Frequently Asked Questions

What is vascular dementia?

It is a decline in thinking, memory, and self-control that is caused by disease of the brain's blood vessels, whether from strokes, small-vessel disease, or chronically reduced blood flow. It is the second most common cause of dementia after Alzheimer's disease, and the two often occur together.

How is it different from Alzheimer's disease?

Alzheimer's disease is defined by a molecular pathology and usually begins with memory loss. Vascular dementia is defined by its cause, which is vascular damage, and typically begins with slowed thinking and difficulty planning and organising, with memory relatively spared until later. In practice the two frequently coexist.

What causes vascular dementia?

Anything that damages the brain's blood supply: large strokes, many small strokes, or disease of the tiny arteries that feed the deep white matter. The underlying risk factors are the same ones that cause heart disease and stroke, especially high blood pressure, along with diabetes, smoking, and irregular heart rhythm.

What are the symptoms?

Common early features are mental slowness, trouble with planning, organising, and concentrating, and changes in mood, with memory often less affected at first than in Alzheimer's disease. When it follows a stroke, the onset can be sudden and tied to the stroke; when it comes from small-vessel disease, it can develop gradually.

Can vascular dementia be prevented?

To a meaningful degree, yes. Because its risk factors are treatable, controlling blood pressure, managing diabetes, stopping smoking, and treating heart rhythm problems all lower the risk. A large trial found that intensively lowering blood pressure reduced the risk of cognitive impairment.

What is small-vessel disease?

It is damage to the brain's smallest arteries, which feed the deep white matter. It leaves two signature marks visible on brain scans: tiny cavities called lacunes and diffuse bright patches called white-matter hyperintensities. It is now considered the most common cause of vascular dementia.

Can vascular dementia be treated?

There is no drug approved to reverse the underlying disease. Treatment focuses on controlling the vascular risk factors to slow further damage, and on managing symptoms. Medicines used for Alzheimer's disease give at best modest benefit in vascular dementia.

Is it possible to have both vascular and Alzheimer's dementia?

Yes, and it is in fact the most common situation in older people. This is called mixed dementia, in which vascular lesions and Alzheimer pathology are both present and compound one another, each making the other more likely to produce symptoms.

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