Moreover, patients who had suffered strokes and other forms of cerebrovascular disease had a lower "threshold" for dementia caused by Alzheimer's and Parkinson's disease.
That is, people started to suffer the cognitive symptoms of dementia at a less advanced stage of these two brain diseases, as determined by the amount of buildup of irregular proteins.
Similar findings have been made in the past. But the new study, from Penn's Perelman School of Medicine, was unusually large - with data from the government-funded National Alzheimer's Coordinating Center on more than 6,000 subjects. And authors said the study was the first to compare multiple neurodegenerative diseases.
John Q. Trojanowski, senior author of the study in the journal Brain, said that while the research does not prove that vascular disease worsens Alzheimer's, it supports the case for maintaining a healthy diet and lifestyle.
"None of this is surprising, but it hadn't been nailed down," said Trojanowski, a professor of pathology and a prominent researcher in the field.
Authors of the study also included Penn's Jon B. Toledo and Steven E. Arnold, among others.
Other studies have shown that the brain starts to develop internal signs of Alzheimer's decades before there is any decline in cognitive performance, Arnold said.
If exercise and diet truly play a role in maintaining a healthy brain, it would be best to get an early start in adopting good habits, he said.
"I'm in my 50s," Arnold said. "What I do now may determine whether I develop dementia when I'm in my 70s or 80s."
Another recent study from Penn, presented last week at the Alzheimer's Association International Conference in Boston, suggests that some at-risk patients are taking this type of message to heart.
Penn's Jason Karlawish and colleagues found that patients who learned they had a high genetic risk of developing Alzheimer's became more active than others in their efforts to exercise and eat healthful food.
These patients also were no more likely to experience anxiety or depression after learning about their genetic risk.
Contact Tom Avril at 215-854-2430 or firstname.lastname@example.org.