So-called vascular risk factors, including obesity, diabetes, smoking, high cholesterol and elevated blood pressure, have been previously linked to higher odds of dementia, cognitive decline and Alzheimer’s disease.
But it’s been unclear whether these factors contribute indirectly by restricting blood flow in the brain, or if they directly cause a buildup of amyloid protein fragments that are linked to Alzheimer’s.
Lead study author Dr. Rebecca Gottesman of Johns Hopkins University School of Medicine in Baltimore said they found an associated between the number of risk factors that people without dementia had when they were middle-aged and the risk of having amyloid in their brain when they were older.
Gottesman said that each alone may not be enough to increase the risk of Alzheimer’s disease, but having a number of these risk factors appears to be associated with an even higher risk. And although this doesn’t prove causation, it suggests that vascular risk factors might directly impact Alzheimer’s changes in the brain, she added.
Alzheimer’s disease is the most common cause of dementia among older adults. The progressive brain disorder slowly erodes memory and thinking skills and eventually leaves people unable to handle basic tasks in daily life. Scientists suspect that changes in the brain begin at least a decade before symptoms appear.
For the current study, researchers examined data from 346 adults who had been evaluated for vascular risk factors since the late 1980s, when they were 52 years old on average and none of them had dementia. More than two decades later, when participants were around 76 years old, they had brain scans that looked for evidence of Alzheimer’s.
At the start of the study, one in five participants had no vascular risk factors, while 38% had one and 42% had at least two.
A higher number of vascular risk factors in midlife, but not in late life, was associated with elevated brain amyloid, researchers report in JAMA.
Brain scans found that 31% of people with no vascular risk factors at the start of the study had elevated amyloid later in life, compared with 61% of the people who had at least two vascular risk factors in middle age.
Relationships between vascular risk factors and brain amyloid didn’t differ by race. There also wasn’t a meaningful difference based on whether people were carriers of what’s known as the ApoE4 allele, a version of a gene that’s associated with increased risk for Alzheimer’s disease.
“Brain amyloid is a risk factor that likely begins prior to the development of memory problems and thus, these findings are very intriguing,” Dr. Jeffrey Burns, co-director of the University of Kansas Alzheimer’s Disease Center in Kansas City, said by email. “We do need to be careful to recognize that amyloid in the brain does not equal Alzheimer’s disease.”