Understanding Vascular Dementia
It affects thinking. It affects how quickly the brain acts and supports how someone is able to function. It affects memory and ability to shift focus. It is vascular cognitive impairment (VCI) — also known as vascular dementia, a disconcerting and frightening term that no one wants to hear in regards to themselves or someone they love.
Dr. Steven Greenberg
Steven Greenberg, M.D., Ph.D., John J. Conway Endowed Chair in Neurology at Massachusetts General Hospital, has studied this disease of the blood vessels in the brain for many years. He says that stroke can cause dementia in two ways. “When somebody has a diagnosed stroke, one of the really important outcomes may be impairment of cognition affecting memory,” he said. This impairment may affect a survivor’s ability to work toward recovering in other areas, like motor functions and speech.
Less obviously, dementia may be caused by silent strokes (a.k.a., silent cerebral infarction (SCI) likely caused by a blood clot interrupting blood flow in the brain). By definition, people are unaware of these and only small areas of the brain are injured. However, these small injuries accumulate over time and produce a result that can look a lot like Alzheimer’s disease. “People use the term neurodegenerative disease to describe any gradual injury of the brain,” Greenberg said. “In vascular cognitive impairment, the main problem is probably loss of blood flow.”
VCI & Alzheimer’s disease
Though Alzheimer’s disease and vascular cognitive impairment have similar outcomes, they have different causes. Alzheimer’s disease results from 1) abnormal protein deposits called beta-amyloid plaques that clump together between nerve cells, and 2) dead and dying nerve cells, called tangles, made of twisted strands of another protein. These develop over years, and symptoms don’t usually appear until the process is well-advanced. On the other hand, VCI is related to deterioration of blood vessels, usually as a result of blood vessel disease, which cause silent strokes. Some people with VCI may have a fullblown stroke, but not all do. “It can creep along just the way Alzheimer’s disease does, getting worse little by little without any sudden changes,” Greenberg said.
Symptoms and differences with AD
There are some subtle differences: Alzheimer’s disease tends to affect memory; vascular cognitive impairment seems to affect other kinds of cognitive skills, like how quickly the brain acts and can handle different tasks (processing speed) or executive function, the ability to shift from one focus to another. “That is not to say that VCI doesn’t affect memory as well,” Greenberg said. “There’s a lot of overlap between the degenerative Alzheimer’s type and the vascular blood vessel type. It’s clear that having both is worse than having either one by itself. It may be that the majority of the people who lose their memory as they get older have more than one thing going on. There’s pretty good evidence that vascular disease plus degenerative disease are the rule and not the exception.”
Like Alzheimer’s, VCI is progressive. It starts with mild impairment of cognitive skills that affects daily functioning — “They can still do the shopping, do the home repairs, pay the bills, but they are often slower and more forgetful,” Greenberg said. The timeline is unpredictable, but as the disease progresses, the functional skills deteriorate, and people start turning things over to other family members or to caregivers, until ultimately they have lost their ability to do even simple day-to-day activities like dressing and washing. VCI can sometimes take a slightly different form from Alzheimer’s disease — “VCI patients are more likely to become withdrawn, apathetic, uninterested in activities,” Greenberg said. “They can look depressed although it’s probably not the same thing as depression. It can be hard for even very experienced clinicians to look at somebody and tell you, ‘I think this is vascular’ or ‘I think this is Alzheimer’s disease.’ The patterns are very similar.”
Atherosclerosis (hardening of the arteries) is implicated in many strokes involving the large arteries like the carotid. This same disease process can also affect the small blood vessels with a similar outcome on a smaller scale, but there are a lot more of those small blood vessels. High blood pressure and diabetes also hasten changes in these vessels the same way they do in the larger ones.
Another cause of small vessel disease is amyloid angiopathy. This is the same amyloid protein at the root of Alzheimer’s, but instead of affecting brain tissue, it affects blood vessels and causes silent strokes, both ischemic and hemorrhagic.
Diagnosis — scans are useful
Although VCI and Alzheimer’s are hard even for clinicians to differentiate by symptoms, some features can be distinguished by MRI scans. When patients come in because of memory loss, the small strokes are visible in the MRI, but there’s no specific marker for Alzheimer’s disease, which can only be definitively diagnosed by autopsy.
In addition to VCI’s tendency to affect processing speed and executive functions, “it’s probably more likely to affect a person’s walking than Alzheimer’s disease,” Greenberg said. So people get slower and have a loss of balance in addition to impaired cognitive function. “Again, none of these things are cleanly diagnostic and most clinicians wait until they get information from the MRI scan.”
The old adage that an ounce of prevention is worth a pound of cure is certainly true in VCI. Cholinesterase inhibitors, which are used in Alzheimer’s, may boost memory a little bit, but there really are no treatments for dementia.
“There are grounds for optimism that we are getting better at preventing vascular cognitive impairment,” Greenberg said. “We really don’t have effective prevention treatments for Alzheimer’s, but for vascular cognitive impairment, we probably do.” It may be that treating heart disease risk factors — lowering blood pressure, preventing or treating diabetes, reducing cholesterol, eating a heart healthy diet and being physically active — are lowering the risk for VCI as well. “There’s real reason to think those will work. Until we have better treatments, they’re the most important treatments we can offer people.”
Aging is the primary risk factor for VCI, and beyond that, what puts someone at risk of stroke increases their risk of VCI. High blood pressure is a major risk factor, and diabetes and high cholesterol also. Although these conditions are present when VCI shows up, their damaging affects begin in middle age (45-55). “Of course, we want people to be heart-healthy and brain-healthy through their whole lives, but certainly midlife is a very promising time to change your lifestyle to lower the risk for cognitive impairment 10 or 20 years later,” Greenberg said.
It may be difficult to distinguish VCI from Alzheimer’s disease, but it is not difficult to see that dementia in general is a huge problem: As many as half of all 85-year-olds have some form of dementia. And maybe not just one form: “There is good reason to think that the mixed form may be the more common form of dementia,” Greenberg said. “No matter how you look at it, these are very high numbers. If we could remove the vascular side of dementia, we could make a major impact.”
Some good news
Even though dementia is increasing because the population is aging, its prevalence in any particular age group is coming down. In a recent article in the New England Journal of Medicine, the authors found that risk ratios for dementia had declined 44 percent in the past four decades — from 3.6 per 100 in the 1970s to 2.0 per 100 in the 2010s. (This only held true for people with at least a high school diploma.) Interestingly, “the prevalence of most vascular risk factors (except obesity and diabetes) and the risk of dementia associated with stroke, atrial fibrillation or heart failure have decreased over time, but none of these trends completely explain the decrease in the incidence of dementia,” the authors said.
“We know that even small decreases will have enormous public health impact as the population ages,” Greenberg said. “If we can delay the average start of dementia by even a few years, that’s a huge amount of the burden being lifted from the population.”
The impact of dementia on families can be enormous, whether the patient is cared for at home, in a nursing home or a memory-care facility. Whichever course is taken, there is a heavy financial impact, be that a loss of earnings for time away from work or the cost of residential care. Generally, the patient prefers to stay at home, but that may not be possible as the condition progresses. A person with dementia may feel anxious, upset or agitated in certain places or when focused on specific details; as a result, they become restless and need to pace or move around. “Agitation is often the strongest predictor of a family deciding that their loved one needs to be moved to some type of facility for care,” Greenberg said.
The degenerative process also creates an emotional burden for the family, as their loved one deteriorates. “One of the things that makes all forms of stroke so burdensome to individuals and to society is that people can live for years in an impaired state, which continues to add to the emotional and financial burden placed on some caregivers,” Greenberg said.
“I don’t think there are any perfect solutions,” he said. “Anyone who has spent time in a long-term care facility knows that it’s unfortunately very easy to have bad situations, patients become unhappy and agitated. Dementia is the challenge and burden for our society, to try to prevent and effectively treat all forms of it. Right now, the vascular component may be the most preventable form, which is to me the unrecognized victory that we should be celebrating — at least it’s a partial victory.”