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Many studies have found that high blood pressure in middle age can boost risks of cognitive decline later in life. But studies examining how high blood pressure in old age affects mental abilities years later have come to conflicting conclusions. Some have found that high blood pressure in old age boosts these risks, while other studies have not.

New Research in the Journal of the American Geriatrics Society

To learn more, researchers recently studied roughly 3,300 men and women over the course of several years. When the study began, 3,000 of the men and women were aged 55 to 84, and nearly 300 were 85 and older.

At the start of the study, the researchers measured each adult's blood pressure. At the end of the study, several years later, they gave each adult tests to measure his or her cognitive abilities. The researchers then grouped the adults by age, and compared the effects of high blood pressure on later mental abilities based on age.

They found that, among the adults who were younger than 75 at the start of the study, those with high blood pressure were, if anything, more likely to have mental decline several years later, than those who didn't have high blood pressure. But among adults who were 75 and older at the start of the study, those who had high blood pressure had better, not worse, mental abilities several years later than those who didn't have high blood pressure.

Why? High blood pressure can, among other things, damage blood vessels and limit the flow of blood and oxygen to the brain, which can lead to mental decline. But other changes that can occur in the "old-old" - those 75 and older - can also limit the flow of blood and oxygen to the brain. Due to age-related changes to the way blood flow to the brain is regulated, the old-old run an increased risk of "hypoperfusion," or insufficient flow of blood, to the brain. This can cause significant cognitive decline. In the old-old, then, higher blood pressure may, in fact, "push" more blood to the brain, preventing hypoperfusion, and the mental decline that accompanies it, the researchers report in the Journal of the American Geriatrics Society.

"There seems to be a gradual shift with age from high blood pressure being a risk factor for cognitive impairment to high blood pressure potentially helping to preserve cognitive function in the oldest old presumably through maintaining perfusion pressure," they write. "Our data illustrate that we should not simply assume that advice to 66-year-olds on target (or ideal) blood pressure should be the same as advice to 85-year-olds on target blood pressure."

What Should I Do?

For more information about high blood pressure in later life, visit http://www.healthinaging.org/agingintheknow/chapters_ch_trial.asp?ch=39.

The summary above is from the full report titled, "The Effect of Age on the Association of Blood Pressure with Cognitive Function Later in Life." It is in the July 2009 issue of the Journal of the American Geriatrics Society (Volume 57, Issue 7). The report is authored by Sjoerd M. Euser, PhD, Thomas van Bemmel, MD, Miranda T. Schram, PhD, Jacobijn Gussekloo, MD, PhD, Albert Hofman, MD, PhD, Rudi GJ Westendorp, MD, PhD, and Monique MB Breteler, MD, PhD.