Mild to moderate high blood pressure seems to slow thinking skills in older people, researchers report in Hypertension: Journal of the American Heart Association.
This study indicates that people should view moderately high blood pressure more seriously, says Gary A. Ford, MD, at the University of Newcastle Upon Tyne, United Kingdom. "Our work suggests that the effects of mild to moderate high blood pressure on cognitive function should be explored."
"A lot of older people are not well treated for this condition and the effects appear to be more serious than previously thought. In nearly every aspect of cognitive function we studied, the people with high blood pressure performed worse than those with normal blood pressure," Ford says. "This suggests that treating high blood pressure might prevent dementia. But we need further studies to establish that." Participants were tested for memory, word and picture recognition, and spatial memory.
Although the changes in thinking skills are too mild to interfere with a person's day-to-day functioning, they might increase the risk of developing dementia, or impaired mental abilities later on, he says.
The prevalence of dementia doubles with every five-year age increase, from 2.8 percent at 70 to 74 years of age to 38.6 percent at 90 to 95 years, and the U.K. population — like that of the United States — is aging, says Ford. As a result, the number of people with cognitive impairment in the U.K. is expected to double in the next 50 years.
"Currently, there are no treatments proven to slow or prevent the development of dementia. It's important that we identify interventions that will reduce the incidence of dementia in older people," Ford says.
Blood pressure also tends to rise with age. Studies indicate that by age 75, an estimated 41 percent of men and 54 percent of women have high blood pressure, which is defined as systolic pressure (the top number) above 140 millimeters of mercury (mm/Hg), and diastolic pressure (the lower number) above 90 mm/Hg. Systolic pressure is when the heart beats, whereas diastolic pressure measures the pressure between heartbeats.
Researchers have speculated that high blood pressure and dementia are related. Long-term studies have found that high blood pressure in mid-life results in reduced thinking skills four to 20 years later. However, other long-term studies have shown conflicting results, perhaps because of certain variables, Ford says.
For instance, blood pressure tends to drop with the onset of dementia or any other condition that causes weight loss, he says. In addition, stroke is associated with dementia, and earlier studies did not attempt to control for stroke. In fact, only one small study of 25 patients with severe high blood pressure tried to exclude the effects of stroke. In addition, drugs to reduce blood pressure might affect the results.
This study attempted to control for variables by matching individuals in the normal and high blood pressure groups. It is the largest study to attempt to exclude the effects of cerebrovascular disease – such as stroke – and the only one to do so when examining moderately high blood pressure. Although none of the subjects with high blood pressure were taking medication for the condition during the study, all of them subsequently started treatment.
Ford and his colleagues compared 107 men and women with high blood pressure (averaging 164/89 mm Hg) to a control group of 116 subjects with more "normal" blood pressure (131/74 mm Hg). The average age in both groups was 76.
They gave participants several tests to determine reaction time, and various kinds of short- and long-term memory such as the ability to remember a list of words, numbers or the details of pictures they had seen.
The people with high blood pressure had slower reaction times and had more trouble remembering things, and were on average 10 percent slower in their simple reaction time than those with normal blood pressure. While this is significant, it is still less than the reaction times seen in individuals with mild dementia. The reaction times of individuals with high blood pressure are one-third to one-half of that seen in people with mild dementia, say researchers.
"These differences are likely a direct effect of hypertension," Ford says. The groups were well matched for other factors known to influence cognitive function: age, education level, depressive disorder and psychotropic medication. |
