Diseases of large and small blood vessels in the brain are not uncommon in the elderly — and may contribute more significantly to Alzheimer’s disease than previously thought, according to researchers at Rush Alzheimer’s Disease Center in Chicago.
“Both large and small vessel diseases have effects on dementia and thinking abilities, independently of one another, and independently of the common causes of dementia such as Alzheimer’s pathology and strokes,” said lead researcher Dr. Zoe Arvanitakis, a neurologist at the center.
The findings of their study showed that the worse the brain vessel disease, the higher the chance of having dementia, which is usually attributed to Alzheimer’s disease. The increase was 20 to 30 percent for each level of worsening severity.
Nearly 47 million people have dementia worldwide, according to Alzheimer’s Disease International, the international federation of Alzheimer associations around the world. By 2050, that number is projected to be 132 million. Therefore, finding ways to treat or prevent the disease “is a major goal,” Arvanitakis said.
For the study, the researchers analyzed medical and pathologic data on 1,143 older individuals (over age 65) from two (RADC) cohort studies: the Religious Orders Study and the Rush Memory and Aging Project. Participants received annual health assessments and agreed to donate their brains for research upon their deaths.
A total of 478 (42 percent) of these participants had developed Alzheimer’s disease. Analyses of the brains showed that 445 (39 percent) of the study participants had moderate to severe atherosclerosis — plaques in the larger arteries at the base of the brain obstructing blood flow — and 401 (35 percent) had brain arteriolosclerosis — stiffening or hardening of the smaller artery walls.
The findings, published in the British journal The Lancet Neurology, showed that atherosclerosis and arteriolosclerosis were linked to a reduction in cognitive skills, including memory, and these associations were present in persons with and without dementia. Furthermore, the worse the brain vessel disease, the higher the chance of dementia.
The study was not designed to determine causation of Alzheimer’s dementia, or even whether vascular disease or Alzheimer’s developed first. “But it does suggest that vessel disease plays a role in dementia,” Arvanitakis said.
“We found that blood vessel diseases are very common in the brain, and are associated with dementia that is typically attributed to Alzheimer’s disease during life.”
In an editorial that accompanied the study findings, it was noted that while other studies have shown that proactive measures like eating a selective diet and getting regular exercise might protect against Alzheimer’s, those interventions might actually be acting on non-Alzheimer’s disease processes, such as cerebrovascular disease.
Arvanitakis says they don’t know yet. “They may decrease actual Alzheimer’s, and possibly even work by yet other pathways,” Arvanitakis said. “We hope to better distinguish how the clinical expression of vessel diseases in the brain differ from those of Alzheimer’s, so that we may eventually use earlier and more targeted treatments for dementia.”
Source: Rush University Medical Center