Researchers in France assessed data on about 3,500 British men and 1,300 British women with an average age of 55 who participated in Whitehall II, a long-term study that tracked British civil servants.
Three times over the course of a decade, participants took tests that measured their reasoning skills, memory, fluency and vocabulary. The reasoning test was composed of 65 verbal and mathematical questions of increasing difficulty, and the memory test asked people to recall a list of 20 words. The fluency test asked participants to do such things as name as many words as they can, in one minute, that start with the letter "s" or name as many animals as they can.
Participants were also given a what's called a Framingham risk score, which takes into account a person's age, gender, cholesterol levels, blood pressure, smoking history and diabetes status to predict the chances of having a heart attack, stroke or other cardiovascular problem sometime in the next 10 years.
Those who had poorer cardiovascular health were more likely to do worse on tests of memory and mental ability than were those who had better cardiovascular health, according to the study.
For example, a 10 percent higher cardiovascular risk score was associated with a 2.8 percent lower score on the memory test for men and a 7.1 percent lower score for women.
Over time, those who had worse cardiovascular health also saw steeper declines in mental tasks, with the exception of reasoning for men and fluency for women.
"We found that cardiovascular risk in middle age is related to lower overall cognitive function," said study co-author Sara Kaffashian, a doctoral student at INSERM, the French National Institute of Health & Medical Research in Paris. "We also observed a relationship between poor cardiovascular scores and overall cognitive decline over 10 years."
The study is to be presented in April at the American Academy of Neurology's annual meeting in Honolulu. Experts note that research presented at meetings has not been subjected to the same rigorous scrutiny given to research published in medical journals.
Dr. Ralph Sacco, president of the American Heart Association, said an increasing body of research is showing the importance of cardiovascular health in maintaining brain function over a person's life span.
"The link between cardiovascular health and brain health is becoming increasingly important and recognized," said Sacco, a professor of neurology, epidemiology and human genetics at the University of Miami Miller School of Medicine.
High blood pressure, diabetes, smoking, high cholesterol and inactivity can contribute to a narrowing of the large blood vessels throughout the body, but also the small blood vessels of the brain, Sacco explained.
Those changes can reduce blood flow, which can "starve the brain of oxygen and lead to changes in thinking, cognition and our mental abilities," he said.
Though the people in the study did not have Alzheimer's, other research suggests that hypertension, diabetes and poor cardiovascular health are a risk factor for both Alzheimer's and vascular dementia, he added.
"In the old days, we thought vascular risk factors only led to vascular dementia, but now we know vascular risk factors may also have an impact on Alzheimer's," Sacco said.
But the good news, he said, is that middle-aged adults can take steps to improve cardiovascular health, including eating a proper diet, exercising, controlling diabetes if they have it and, if applicable, taking the correct medications for hypertension, Sacco said.
"There is a hopeful note, which is that by controlling your vascular risk factors, you may be able to reduce or forestall cognitive decline," he said.