Wide fluctuations in blood pressure may be associated with memory and thinking difficulties in older adults already at high risk for heart disease, a new European study suggests.
Regardless of average blood pressure, "high variability in blood pressure may lead to mental impairment," said lead researcher Dr. Simon Mooijaart, director of the Institute for Evidence-Based Medicine in Old Age in Leiden, the Netherlands.
The three-year study, published July 30 in the online edition of the BMJ, involved more than 5,000 seniors, average age 75.
Fluctuating blood pressure has previously been linked with an increased risk of stroke, and evidence is mounting that factors that disrupt blood flow to the brain contribute to dementia's development and progression, the researchers noted.
However, because the study shows only an association, not a cause-and-effect relationship, Mooijaart cautioned that it is still too early to make definitive claims about blood pressure inconsistency and mental decline.
"It's an interesting association, because it might very well be causal," he said. If it is causal, controlling these fluctuations with blood pressure medication might help reduce the risk of dementia, Mooijaart added. But further research is needed, the study authors noted.
"It's very important to keep your vasculature healthy to prevent detrimental effects to your body," Mooijaart said.
Another heart expert agreed.
"Variability in blood pressure readings has been shown to be associated with greater risk of heart attack and stroke, independent of average blood pressure readings," said Dr. Gregg Fonarow, a professor of cardiology at the University of California, Los Angeles, and a spokesman for the American Heart Association.
Blood pressure medications can reduce fluctuations and lower the risk of cardiovascular events, stroke and, some studies suggest, decline in mental function, he added.
"Physicians and patients with hypertension should increase focus on keeping blood pressure levels consistently at goal levels minimizing, to the extent possible, fluctuations in blood pressure," Fonarow said.
To gauge the effect of blood pressure changes on mental ability, Mooijaart's team collected data on more than 5,400 men and women, aged 70 to 82, who took part in the Prospective Study of Pravastatin in the Elderly at Risk. That study, conducted by centers in Ireland, Scotland and the Netherlands, looked at whether lowering cholesterol protected people at risk for heart disease.
Over three years of follow-up, participants' blood pressure was checked every three months. Researchers looked at the variability in those readings and tested participants' mental functioning. Specific tests evaluated attention, reaction time and memory.
Mooijaart's team found that people whose blood pressure varied from visit to visit performed worse on all of the tests than those with stable readings. These results persisted after the researchers accounted for cardiovascular disease and average blood pressure.
But Mooijaart said it isn't clear whether blood pressure variability is a cause or consequence of impaired mental function.
Several explanations may exist for this connection, he said. It's possible that blood pressure variability and mental impairment both result from cardiovascular risk factors. Or blood pressure variability might be a sign of long-term instability in blood flow to vital organs. Another possibility is that blood pressure fluctuations could deprive the brain of blood, which might lead to poorer mental functioning, Mooijaart noted.