The answer depends on how cases are counted, and experts don’t fully agree. Vascular dementia has traditionally been ranked as the second most common type of dementia after Alzheimer’s disease, accounting for roughly 15% to 20% of cases. However, Mayo Clinic and other leading institutions now identify Lewy body dementia as the second most common type, partly because improved diagnostic methods have revealed it was historically underdiagnosed. In practice, vascular dementia and Lewy body dementia are close in prevalence, and many people have overlapping pathology. Since both are frequently searched as “the second most common,” here’s what you should know about each.
Vascular Dementia: Caused by Reduced Blood Flow
Vascular dementia develops when blood flow to the brain is reduced or blocked, damaging brain tissue over time. This can happen after a major stroke that hits a region critical for thinking, like the thalamus or frontal lobe. It can also build up silently through a series of small strokes that individually cause no obvious symptoms but collectively erode cognitive function.
The most common underlying cause is small vessel disease, where the tiny arteries supplying the brain’s deep white matter become damaged. This leads to scattered areas of dead tissue (called lacunar infarcts) and widespread white matter damage. Over time, chronic low blood flow triggers inflammation, oxidative stress, and further vascular injury, creating a cycle that progressively worsens cognition.
How Vascular Dementia Feels Different
Vascular dementia often looks and feels different from Alzheimer’s. While Alzheimer’s typically starts with memory loss, vascular dementia is more likely to begin with problems in planning, organizing, and processing speed. Thinking may feel slower and foggier rather than forgetful.
Depression and anxiety are significantly more common and more severe in vascular dementia than in Alzheimer’s, even when overall cognitive decline is similar. Blunted emotions, low motivation, and withdrawal from activities affect more than a third of people with the condition. This likely reflects the different brain regions involved: vascular damage often hits areas that regulate mood and behavior, not just memory. The progression can also differ. Rather than a slow, steady decline, people with vascular dementia sometimes experience sudden drops in function, often following a new stroke, with stable periods in between.
Risk Factors You Can Control
Because vascular dementia is rooted in blood vessel damage, its risk factors overlap heavily with those for heart attack and stroke. High blood pressure is the single biggest risk factor. Diabetes, high cholesterol, smoking, and atrial fibrillation all significantly increase the likelihood of developing the condition. These same factors have also been linked to a faster rate of decline in people who already have cognitive symptoms.
This overlap is actually encouraging, because it means many risk factors are modifiable. Managing blood pressure, controlling blood sugar, quitting smoking, and staying physically active all reduce the chances of vascular damage reaching the brain. Unlike Alzheimer’s, where the primary drivers are less controllable, vascular dementia is one of the more preventable forms of cognitive decline.
Lewy Body Dementia: A Different Profile
Lewy body dementia is caused by abnormal protein deposits (called Lewy bodies) that build up in brain cells. It shares some features with both Alzheimer’s and Parkinson’s disease but has its own distinctive pattern. Visual hallucinations often appear early, sometimes before significant memory loss. People commonly experience dramatic fluctuations in alertness throughout the day, going from relatively sharp to confused and drowsy within hours. Movement problems similar to Parkinson’s, including stiffness, slow movement, and shuffling gait, are also typical.
Sleep disturbances are another hallmark. Many people with Lewy body dementia physically act out their dreams, sometimes violently, a condition that can precede other symptoms by years. This constellation of symptoms (hallucinations, fluctuating cognition, movement changes, and sleep disruption) is what sets Lewy body dementia apart from other types.
Mixed Dementia Is More Common Than Expected
One reason the rankings are debated is that many people don’t have just one type of dementia. Autopsy studies reveal that about 20% to 22% of elderly people with dementia have mixed pathology combining Alzheimer’s and vascular disease. Some studies have found mixed lesions in as many as 35% of cases. This means a substantial number of people diagnosed with Alzheimer’s during their lifetime also had significant vascular damage contributing to their symptoms, and vice versa. The boundaries between dementia types are much blurrier than the categories suggest.
Diagnosis and Brain Imaging
For vascular dementia, brain imaging is considered essential. MRI is preferred over CT scans because it’s more sensitive at detecting the white matter damage, small infarcts, and strategic strokes that characterize the condition. A diagnosis of “probable” vascular dementia requires both clinical symptoms and visible evidence of cerebrovascular disease on imaging. Without imaging, misdiagnosis rates climb significantly because silent strokes and white matter damage are invisible to a standard clinical exam.
Doctors look for specific imaging findings: large vessel infarcts, multiple small lacunar infarcts, extensive white matter lesions, or strategically placed damage in areas like the thalamus or basal ganglia. The cognitive testing component requires that decline is substantial enough to interfere with daily independence, such as managing finances or medications.
Treatment and Life Expectancy
There is no cure for vascular dementia, but its progression can potentially be slowed. The strongest recommendation from clinical guidelines is to manage blood pressure to standard targets and reduce stroke risk. For people with vascular risk factors, more aggressive blood pressure control (targeting a systolic reading below 120) may offer additional protection against cognitive decline. Stroke prevention strategies are recommended for all patients with known or suspected vascular contributions to their cognitive symptoms.
Medications originally developed for Alzheimer’s, specifically cholinesterase inhibitors, are sometimes used in vascular dementia and may help selected patients, though the evidence is weaker than it is for Alzheimer’s. The core of treatment remains cardiovascular risk management: controlling blood pressure, managing cholesterol, staying active, and eating well.
On average, people with vascular dementia live about five years after symptoms begin, which is somewhat shorter than the average for Alzheimer’s. Because vascular dementia shares risk factors with heart disease, many people ultimately die from a stroke or heart attack rather than from the dementia itself. But progression varies widely. Some people decline quickly, especially after additional strokes, while others remain relatively stable for extended periods when vascular risk factors are well controlled.