Researchers have known for some time that cardiovascular problems in middle and later adulthood may cause cognitive deficits as we age. But surprisingly, there has been little, if any, research into whether high blood pressure, elevated blood glucose and high cholesterol earlier in adulthood have the same effect. A new study by University of California, San Francisco researchers shows that they may, providing another reason to pay attention to fitness and cardiovascular health early in life.
"The fact that we’re able to see [the association] so early is kind of amazing, and it’s kind of sobering and exciting," said Kristine Yaffe, a professor of psychiatry and neurology at UCSF, who led the study. "We know [these connections are] true for the heart, and now we know it’s true for the brain."
Specifically, Yaffe and her team showed that people between the ages of 18 and 30 with the three health problems, which are indicators of poor cardiovascular health, and diabetes, performed worse on tests of memory, "executive function" -- the ability to plan, organize and pay attention to detail -- and mental processing speed than those without the health difficulties. Worse, the effects appear to be cumulative: the longer your blood pressure, fasting blood sugar and cholesterol levels are above recommended levels, the greater your chances for deficits later.
About the only glimmer of good news in the study is that elevated cholesterol does not appear to have as much impact as abnormal blood pressure and blood sugar. Also, the cardiovascular problems are not linked to dementia later in life.
"We can say that almost for sure they don’t have dementia," Yaffe said. "All we can say is that the cognitive scores are different, depending on their exposure to these risk factors."
The researchers gave cognitive tests to 3,381 people during the 25th year of a long-term study of cardiovascular problems. They wrote that "to our knowledge, this study is one of the first" to investigate the possible link between cardiovascular risk factors in early life and cognitive function in mid-life.
They found that "greater cumulative exposure to these measures in levels above recommended guidelines over 25 years was consistently associated with worse cognitive performance on executive function, processing speed and verbal memory," they wrote in the study, published online March 31 in the journal Circulation.
The reasons for that aren't clear, they wrote, but they speculated that these kinds of circulatory problems might limit blood flow to the brain or even damage the brain's blood vessels in ways that aren't apparent until the tests are given.
One limitation of the study is that researchers did not have baseline data on the participants' cognitive function, so they could not compare their performance on the tests over time. So the comparison was between people with the risk factors and those without them.
Yaffe said the results may mean that similar research should be done with even younger people, and that health officials may want to consider recommending even tighter control of blood pressure, cholesterol and blood sugar levels.