VANCOUVER—Alzheimer’s disease may increase stroke risk, and vice versa, according to research presented at the 2012 Alzheimer’s Association International Conference.
Mounting evidence suggests that Alzheimer’s disease and cerebrovascular disease often are comorbid, and an animal study indicates that the diseases may interact, said Vladimir Hachinski, MD, Professor of Neurology and Epidemiology at the University of Western Ontario in London, Canada. If the study results are replicated in humans, neurologists may potentially delay dementia onset by treating patients with antiamyloid and anti-inflammatory therapies before cognitive symptoms are clinically observed.
Alzheimer’s Disease Was Linked With Larger Infarcts
Dr. Hachinski and colleagues devised a rat model to examine the interaction between cerebrovascular disease and Alzheimer’s disease. The investigators found that cerebral infarcts were larger in animals with amyloid-beta deposition than they were in control animals. After three weeks, cerebral infarcts nearly doubled in size in animals with beta-amyloid deposition, but they decreased by approximately half in control animals.
In addition, inflammation was greater in animals with brain amyloid, compared with control animals. With time, inflammation increased in animals with brain amyloid but decreased in control animals. Dr. Hachinski and colleagues are studying whether cerebrovascular disease and Alzheimer’s disease interact in a similar way in the human brain. The researchers are labeling amyloid-beta and activated microglia through PET in acute stroke patients.
The Canadian Study of Health and Aging
Data from the Canadian Study of Health and Aging have shown a correlation between the risk of dementia and the risk of stroke, noted Dr. Hachinski. Of individuals older than 65 who had a stroke, 64% had subsequent cognitive impairment. About 24% of Canadians older than 65 with dementia have had a stroke. “Having risk for one seems to impart a risk for the other,” said Dr. Hachinski.
Approximately 8% of Canadians age 65 or older have had a stroke, and about the same percentage has developed dementia. “For each individual that has either stroke or dementia, there are two that have cognitive impairment that is short of dementia,” said Dr. Hachinski. “Therefore, we should be using cognitive instruments as a screening test for future stroke and development of Alzheimer’s disease.”
The Framingham Offspring Study
Similar to the Canadian Study of Health and Aging, the Framingham Offspring Study suggests a correlation between cognitive test results and the likelihood that a patient will develop a stroke within the next 10 years, observed Dr. Hachinski. Although the Framingham study does not show a correlation between stroke risk and memory impairment, it indicates a strong correlation between change in executive function and risk of stroke. Thus, executive dysfunction may be an early warning of impending stroke or dementia, said Dr. Hachinski.
An unpublished study of 140 consecutive patients with transient ischemic attack or minor ischemic stroke provides further evidence of a link between stroke and Alzheimer’s disease. Nearly 40% of patients in the study had executive dysfunction. “We need to use common minimal standards describing dementia clinically, neuropsychologically, and conceptually,” and early executive dysfunction should be considered a probable hallmark of cerebrovascular disease, said Dr. Hachinski. “We should be using cognitive instruments as a screening test for future stroke and development of Alzheimer’s disease,” he added.
Managing Risk Factors to Prevent Alzheimer’s Disease
Alzheimer’s disease and stroke have many risk factors in common, such as cardiovascular disease, hypertension, obesity, diabetes, and smoking. Controlling these risk factors through medication or lifestyle changes can prevent early stroke and may thus reduce the risk of Alzheimer’s disease, according to Dr. Hachinski.
Lack of adherence to a healthy lifestyle accounts for 35% of all strokes in men and 47% of all strokes in women, said Dr. Hachinski. Unhealthy lifestyles account for 52% of ischemic strokes in men and 54% of ischemic strokes in women. “We know that potentially up to 90% of strokes could be prevented,” Dr. Hachinski observed.
Attention to risk factors and lifestyle has contributed to a decline in the number of severe strokes and delayed the average onset of a patient’s first stroke, he added. In the past 50 years, physicians also have delayed the average onset of heart failure by nearly 20 years, and neurologists might similarly be able to postpone the onset of Alzheimer’s disease, said Dr. Hachinski. “If we could delay the onset of Alzheimer’s disease by one year, prevalence would fall by 20%,” he concluded.
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