Lower Blood Pressure May Protect Against Cognitive Decline in Adults in Their 70s

Hypertensive septuagenarians with the lowest levels of systolic blood pressure (BP) have the smallest declines in cognitive function over time, a new analysis shows, suggesting that lower treatment goals may be appropriate.

Scores on cognitive tests fell regardless of the level of systolic BP, but the drops were greater in people with readings of 150 mm Hg or higher than in those with readings that did not exceed 120 mm Hg, researchers led by Ihab Hajjar, MD (Emory School of Medicine, Atlanta, GA), report in a study published online August 21, 2017, ahead of print in JAMA Neurology.

“Conflicting guidelines have been issued regarding the management of hypertension in older adults, with the main concern being that lower targets are linked to poorer cognitive performance. These concerns have led to a higher [systolic BP] target recommendation for elderly patients,” the authors note. “However, the results of SPRINT have suggested that, from a cardiovascular perspective, this link may not be completely accurate.

“The present study suggests that target [systolic BP] levels of lower than 140 mm Hg and possibly 120 mm Hg or lower extend to cognitive outcomes as well,” they continue. “These issues are critical for defining the concept of blood pressure control, for clinical guidelines and recommendations, as well as for quality-based assessments of healthcare.

Interplay of Systolic BP, Race

Appropriate BP goals are currently an area of uncertainty, stemming from conflicting guidelines and potentially practice-changing results from recent randomized trials. A group of experts empaneled as the Eight Joint National Committee (JNC 8) released recommendations at the end of 2013 that called for less aggressive management than what was advised by JNC 7. The recommendations, which were not ultimately endorsed by any major organization, included a target of 150/90 mm Hg for adults 60 and older who do not have chronic kidney disease or diabetes and a goal of 140/90 mm Hg for younger patients and those with either of the aforementioned diseases.

About 2 years later, the SPRINT trial showed that treating to a systolic goal of less than 120 mm Hg versus a more traditional goal of less than 140 mm Hg improved outcomes in nondiabetic patients with high cardiovascular risk. There is concern, however, that lowering BP too aggressively could harm cognitive outcomes.

To explore that issue, Hajjar and colleagues turned to the Health Aging and Body Composition (Health ABC) study, which included adults ages 70 to 79. The current analysis included 1,657 participants (mean age 73.7; 47.3% black) who did not have cognitive problems and were being treated for hypertension.

Cognitive function was assessed at various time points between 1997 and 2007 using the Modified Mini-Mental State Examination (3MSE), which measures global cognitive function, and the Digit Symbol Substitution Test (DSST), which assesses visuomotor speed, attention, set shifting, and memory. At each visit, participants were categorized according to their BP, taken as an average of two seated readings.

During the study period, declines in 3MSE and DSST scores were greatest in patients with a systolic BP of 150 mm Hg or higher (drops of 3.7 and 6.2 points, respectively) and lowest in patients with systolic BP of 120 mm Hg or lower (declines of 3.0 and 5.0 points, respectively).

The rates of cognitive decline varied based on race as well. Black patients had greater reductions in 3MSE scores compared with whites (4.1 vs 2.6 points; P < 0.001), although drops in DSST scores did not differ by race.

Differences in cognitive decline between higher and lower systolic BP levels also were larger in black versus white participants, suggesting that black patients would potentially derive a greater cognitive benefit from lower BP.

”The finding that lower [systolic BP] was especially protective for black individuals is important given a noted disparity in rates of dementia, with higher rates seen in black individuals,” Rachel Gottesman, MD, PhD (Johns Hopkins University School of Medicine, Baltimore, MD), says in an accompanying editorial.

“Adding to that the finding that hypertension is more common and more severe in black than in white individuals (also supported by the data in this study), and that black individuals tend to have more poorly controlled hypertension than do white individuals, this outcome points to an important opportunity from a public health standpoint,” she continues. “Blood pressure reduction might actually reduce the rates of dementia and reduce the disparities by race with regard to dementia rates; the fact that blood pressure control may require more medications for black individuals than for white individuals needs to be considered when monitoring patients’ blood pressure levels.”

Unanswered Questions

Gottesman also points out some remaining areas of uncertainty, including whether starting antihypertensive therapy at age 70 can stall cognitive decline.

In addition, she notes, the differences in cognition observed could be due to factors other than systolic BP—compliance, access to care, level of education, and number of antihypertensives taken, for example—that are not adequately captured in observational studies like this one. Moreover, the findings might have been influenced by the loss to follow-up of individuals at higher risk for poor cognitive outcomes, she indicates.

“Although unanswered questions remain, these data add to the existing literature by emphasizing that tight blood pressure control does not appear to lead to poorer cognitive trajectories in older adults and may even be associated with improved cognitive trajectories,” Gottesman says.

“The MIND (memory and cognition in decreased hypertension) component of SPRINT, which is ongoing, will provide more direct data on the cognitive outcomes associated with intensive blood pressure control,” she adds. “It will be important to consider cognitive outcomes in this trial in older versus younger adults, as well as in distinct racial groups, to evaluate whether tight blood pressure control is equally safe in both age groups, and whether it is particularly effective in either racial group.”