LOS ANGELES —Treating stroke and dementia’s common risk factors may help ward off both diseases, said Vladimir Hachinski, CM, MD, DSc, in a lecture at the International Stroke Conference 2016. Effective stroke prevention efforts in Ontario may have concurrently reduced the incidence of dementia, he said. Stroke and dementia have many of the same risk factors, including hypertension, hypercholesterolemia, obesity, and diabetes. All of the major dementias have a vascular component, and stroke increases dementia risk. Further interactions may relate the diseases, including blood pressure’s effect on amyloid buildup and the effect of amyloid on inflammation and lesion size after stroke, said Dr. Hachinski, Professor of Neurology and Epidemiology at the University of Western Ontario in London, Canada.
Luciano Sposato, MD, MBA, Dr. Hachinski, and colleagues reported in the December 2015 issue of JAMA Neurology that a decline in stroke incidence in Ontario corresponded with a decline in dementia incidence in the same population. Between 2002 and 2013, the age- and sex-standardized rate of stroke decreased by 32.4%, and the rate of dementia decreased by 7.4%.
“For the past 12 years, the incidence of stroke in Ontario has been decreasing steadily, and for the past six years, it has been decreasing in dementia as well,” Dr. Hachinski said. “Now we are trying to establish to what extent and what kind of relationship there is between stroke incidence and dementia incidence.”
Investigators are using three approaches. First, they are evaluating the relationship mathematically using targeted maximum likelihood estimation. Second, they are studying the prevalence and control of risk factors. Finally, they are assessing whether a decrease in stroke mortality in five Canadian provinces with integrated systems of stroke care, reported by Ganesh et al in the March 8 issue of Neurology, also “is reflecting itself in a decrease in the incidence of dementia.” The retrospective study found that hospitals in provinces with stroke systems were more likely to care for patients on a stroke unit and to have timely access to a stroke prevention clinic.
Initial research suggests that the prevalence of risk factors in Ontario is increasing, which may be due in part to increased detection, Dr. Hachinski said. The risk factors appear to be better controlled, however. “For example, in Ontario there is an increased use of antihypertensive agents, and also the use of statins has really spiked,” he said.
Stroke and dementia often coexist, and the ways in which the diseases interact with each other and with common risk factors may not receive enough attention. Each of the major dementias has a vascular component, ranging from 61% of frontotemporal dementia cases to 80% of Alzheimer’s disease cases. “The presence of a vascular component doubles the chances that Alzheimer’s pathology, which is very common in the elderly, will manifest as dementia,” said Dr. Hachinski. “So, in principle, if we control the vascular factors, we could prevent almost half of the dementias in the neurodegenerative group.”
Researchers have documented various interactions between vascular risk factors and Alzheimer’s disease pathology, Dr. Hachinski noted. Rodrigue et al found that hypertension increases amyloid deposition, especially in APOE4 carriers. Nation et al found that pulse pressure is associated with amyloid and tau markers in CSF, and Hughes et al found that arterial stiffness is associated with increased amyloid deposition. Hooshmand et al reported that higher homocysteine levels are associated with increased tau deposition at autopsy.
“If we integrate stroke and dementia prevention strategies, we can go much further, not only in preventing stroke, but a sizeable number of dementias,” Dr. Hachinski said.
To that end, he led a committee that updated the World Stroke Day proclamation for 2015 to include statements about potentially preventable dementias. Twenty-two international organizations dedicated to Alzheimer’s disease, stroke, and dementias signed the proclamation.
“Probably one of the reasons that so many organizations were able to sign on to a single document is that it’s such common sense,” Dr. Hachinski said. “If the risk factors are the same and the protective factors are the same, it makes sense that we should do that together.”
If the stroke and dementia communities work together, first by conducting joint sessions and exploring possible projects, “we can make a bigger difference,” he said.