An Emory study published this week in JAMA Neurology examines how various systolic blood pressure (SBP) targets for older patients receiving treatment for hypertension were associated with cognitive function and whether racial differences existed in long-term cognitive outcomes.
Systolic blood pressure, the amount of pressure exerted by the heart as it pumps blood throughout the body, is the top or first number in a blood pressure reading.
"The relationship between high blood pressure and the risk for mental decline has long been established. But the ideal systolic blood pressure for older adults has been less clear, with various recommended targets ranging from 120 mm Hg to 150 mm Hg," says lead researcher Ihab Hajjar, MD, MS, associate professor of medicine and neurology at Emory University School of Medicine.
The Eighth Joint National Committee (JNC-8) recommended treating systolic blood pressure (SBP) to a target below 150 mm Hg in older adults, while the Systolic Blood Pressure Intervention Trial (SPRINT) suggested a SBP level lower than 120 mm Hg decreases cardiovascular event rates.
In the observational study, Hajjar and colleagues studied 1,657 cognitively intact older adults from the Health Aging and Body Composition (Health ABC) study. A total of 908 participants were women and 784 were black, with a mean age of 73.7. All participants received treatment for hypertension and were studied for a decade, from 1997 to 2007.
During the Health ABC study, cognition was assessed using the Modified Mini-Mental State Examination (3MSE) four times and the Digit Symbol Substitution Test (DSST) five times. At each visit, participants were classified as having an SBP level of 120 mm Hg or lower, 121 to 139 mm Hg, 140 to 149 mm Hg, or 150 mm Hg or higher based on the mean SBP level of two seated readings.
The Emory researchers found that a greater decline in cognitive scores was associated with patients with SBP of 150 mm Hg or higher and less decline in those with SBP of 120 mm HG or lower. The findings suggest a lower SBP target for black patients may be associated with greater cognitive benefits.
"Overall, our analysis suggests that lower systolic blood pressure levels are associated with greater cognitive protection in older adults," says Hajjar. "A blood pressure below 140 in treated hypertensive older adults is not associated with worsening cognitive function. It also suggests that a lower level is more important in African Americans being treated for hypertension."
Over a 10-year period, the greatest decline in cognitive status was seen in people with SBP levels of 150 mm Hg or higher (adjusted decrease was 3.7 for 3MSE and 6.2 for DSST). Conversely, the least cognitive decline occurred in those with SBP levels of 120 mm Hg or lower (adjusted decrease was 3.0 for 3MSE and 5.0 for DSST).
The results showed significant racial differences in the progression of cognitive function. Black participants had a greater mean 10-year decrease in 3MSE scores (–4.1 [0.4]; P<.001) compared with white participants (–2.6 [0.3]; P<.001; P<.001 for race × year) after adjusting for covariates and baseline performances.
However, similar results were not found with DSST -- with the mean 10-year decrease of -5.8 (0.4) for white participants (P<.001) and -4.7 (0.4) for black participants (P<.001; P=.09 for race × year).
Additionally, compared with white participants, black participants had a greater difference between the higher and lower SBP levels in the decrease in cognition.
Hajjar and colleagues advised that future guidelines should consider this racial difference when reviewing or providing recommendations for the management of hypertension.