One of the challenges inherent in identifying meaningful associations in aging is that degeneration is a global phenomenon: every tissue accumulates damage and becomes increasingly dysfunctional. It may be that for any two features of aging you care to compare, the only underlying link is that damage occurs. People with more damage have more dysfunction in both areas, people with less damage have less dysfunction in both areas. It isn't necessarily the case that these two features have any direct interaction with one another at all. It's worth bearing this in mind when reading the results of correlation studies in aging, as there has to be a much better argument than just the fact of correlation to establish a link of causation:
Even for elderly people with no signs of dementia, those with hardening of the arteries are more likely to also have the beta-amyloid plaques in the brain that are a hallmark of Alzheimer's disease. "This is more evidence that cardiovascular health leads to a healthy brain."
The study involved 91 people with an average age of 87 who did not have dementia. Researchers took scans of the participants' brains to measure any plaques in the brain. The amount of stiffness in the participants' arteries was measured about two years later. Half of all participants had beta-amyloid plaques. People with beta-amyloid plaques were more likely to have high systolic blood pressure, higher average blood pressure and higher arterial stiffness as measured with the brachial-ankle method. For every unit increase inbrachial-ankle arterial stiffness, people were twice as likely to have beta-amyloid plaques in the brain.
Arterial stiffness was highest in people who had both amyloid plaques and white matter hyperintensities in the brain, or brain lesions. "These two conditions may be a 'double-hit' that contributes to the development of dementia. Compared to people who had low amounts of amyloid plaques and brain lesions, each unit of increase in arterial stiffness was associated with a two- to four-fold increase in the odds of having both amyloid plaques and a high amount of brain lesions. This study adds to growing evidence that hardening of the arteries is associated with cerebrovascular disease that does not show symptoms. Now we can add Alzheimer's type lesions to the list."