November 16, 2009
High blood pressure was linked to memory and thinking problems in people over 45, according to findings from a large study, possibly setting the stage for problems like Alzheimer's and other forms of dementia later in life. The findings appeared in Neurology, the medical journal of the American Academy of Neurology.
For every 10 point increase in diastolic blood pressure, which is the lower number on the blood pressure reading, a person had a 7 percent increased risk of having difficulties with memory and thinking. Normal blood pressure is usually considered to be around 120/80, with 80 being the diastolic reading. High blood pressure, in this study, was defined as a reading of 140/90 or higher, or taking a medication for the condition.
Alzheimer's and other forms of dementia affect about 8 percent of Americans age 65 and older. High blood pressure is far more common in seniors, affecting about 65 percent. However, the relation between Alzheimer's and blood pressure remains uncertain. Some studies have found a link between high blood pressure and memory problems; others a link between low blood pressure and memory loss; while still others have found no link at all.
The current study involved nearly 20,000 Americans age 45 and older from across the country. All were part of the Reasons for Geographic And Racial Differences in Stroke, or REGARDS Study, one of the largest population-based studies of risk factors for stroke. None of the study participants had ever had a stroke or a so-called "mini-stroke," a transient form of stroke that can damage the brain.
The researchers found that 1,505 of the participants, or 7.6 percent, had cognitive problems, and 9,844, or 49.6 percent, were taking medication for high blood pressure. In their analysis, the researchers considered other factors that may raise the risk for Alzheimer's, including advancing age, being a smoker, getting little exercise, having few years of forming schooling, or having medical conditions like diabetes or high cholesterol. High blood pressure was independently linked with cognitive problems in middle age and beyond.
"It's possible that by preventing or treating high blood pressure, we could potentially prevent cognitive impairment, which can be a precursor to dementia," said study author Dr. Georgios Tsivgouli, of the University of Alabama at Birmingham.
Other scientific studies have shown that high diastolic blood pressure leads to weakening of small arteries in the brain, which can result in the development of small areas of brain damage. Dr. Tsivgoulis said more research is needed to confirm the relationship between high blood pressure and cognitive impairment.
The National Institutes of Health is now organizing a large clinical trial to evaluate whether aggressive blood pressure lowering can decrease a number of important health outcomes including cognitive decline.
G. Tsivgoulis, M.D., A. V. Alexandrov, M.D., V. G. Wadley, Ph.D., et al: "Association of Higher Diastolic Blood Pressure Levels With Cognitive Impairment." Neurology, Volume 73, August 24, 2009, pages 589 -- 595.