Elderly Blood Pressure Variability Affects Cognitive Function
A new study presented today indicates that cognitive function is adversely affected by exaggerated blood pressure variability, or the difference between systolic and diastolic readings, in elderly patients 80 years of age and older.
Presented in New York City at the 21st Annual Scientific Meeting of the American Society of Hypertension (ASH 2006), the study measured blood pressure and cognitive function in 101 Japanese outpatients receiving treatment for chronic diseases such as hypertension, hyperlipidemia, diabetes, chronic gastritis, and osteoporosis.
“Although clinicians may be reluctant to treat older patients aggressively, perhaps because of perceived lower benefits or possible increased risk of medication side effects, these findings show the potential value of interventions,” said Kenichi Sakakura, M.D. of the Public Kiwa Clinic in Kumano, Mie, Japan.
The purpose of the study was to evaluate the association between pulse pressure and cognitive function in the very elderly, specifically those over 80 years old. Blood pressure was measured via 24-hour ambulatory blood pressure monitoring (ABPM) and evaluations of cognitive function utilized the Mini-Mental State Examination (MMSE), an 11-question measure with a maximum score of 30 points, that tests five areas of cognitive function: orientation, registration, attention and calculation, recall, and language. Cognitive dysfunction was defined by the score of the MMSE. There are several cut-off points for the MMSE (22 points - 26 points) and 24 points was chosen as the cut-off point because all of the patients in the study were 80 years of age and older.
Results showed 24-h systolic BP: 138.1 + 17.6 mmHg; 24-h diastolic BP: 75.9 + 8.0 mmHg. Mean MMSE score was 23.1 ± 4.2, and of those, 55.4 percent of patients were diagnosed with cognitive dysfunction (<24 points). MMSE scores decreased across the tertiles of standard deviation of systolic blood pressure readings (SBP) (P=0.02), indicating lower functioning, but remained significant after controlling for daytime SBP levels, confirming an independent relationship between exaggerated blood pressure variability and cognitive dysfunction in the elderly.
ABPM takes numerous blood pressure readings over a 24-hour period, and is considered the most accurate measurement of blood pressure in day-to-day clinical practice. The MMSE is a series of questions and tests and is most commonly used to evaluate memory problems in patients suspected of having dementia. Standard deviation (SD) of daytime systolic blood pressure (SBP) was also calculated as a measure of blood pressure variability.
Previous research that was published in Hypertension: Journal of the American Heart Association in 2004 evaluated blood pressure effects on cognitive performance on 529 patients who were divided into two age groups: 18 to 46 years and 47 to 83 years. The data showed that there was a correlation between higher blood pressure and decline in cognitive function over time in both age groups. The lead investigator suggested that lowering the systolic blood pressure by 20mmHg or diastolic blood pressure by 10mmHg would have a considerable beneficial effect on the preservation of cognitive abilities in the whole population.
Calling for deeper investigation, Dr. Sakakura also said, “These results further validate previous indications that variable blood pressure has an effect on cognitive function in the very elderly. However, very little data exists to support these theories, and more research is needed to confirm the full impact of blood pressure on cognitive function in these patients.”
American Society of Hypertension (ASH)
Revision date: June 20, 2011
Last revised: by Andrew G. Epstein, M.D.