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Lower systolic blood pressure (SBP) levels are associated with greater cognitive protection in older adults -- specifically older black adults -- receiving treatment for hypertension, reported researchers.

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 Modified Mini-Mental State Examination (3MSE) and 6.2 for Digit Symbol Substitution Test (DSST)], reported Ihab Hajjar, MD, MS, of the Emory School of Medicine in Atlanta, and colleagues.

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 team wrote online in : "This analysis of 10-year data from older adults receiving treatment for hypertension in the Health ABC study suggests that lower SBP levels are associated with greater cognitive protection."

Lower SBP targets, such as those recommended by JNC-7 or used in SPRINT, are overall superior to those of JNC-8 in terms of cognitive perspective, the team added.

The Eighth Joint National Committee (JNC-8) recommends treating SBP to a target below 150 mm Hg in older adults while the Systolic Blood Pressure Intervention Trial (SPRINT) suggests a level lower than 120 mm Hg.

More recently, the American College of Physicians and American Academy of Family Physicians proposed a looser target of for lower-risk adults age 60 and older and less than 140 mm Hg for people in the same age range with prior stroke, transient ischemic attack, or high cardiovascular risk.

, Rebecca F. Gottesman, MD, PhD, of Johns Hopkins University School of Medicine in Baltimore, wrote that the data provide "important support for a lack of harm from lower attained blood pressure in adults older than 70 years of age on 10-year cognitive trajectories."

However, she also noted that the data "do not convincingly answer the question of the safety of iatrogenically lowering SBP below 120 mm Hg in older adults in terms of cognitive outcomes."

Hajjar and colleagues studied 1,657 cognitively intact older adults from the Health Aging and Body Composition study from communities in Pittsburgh, Penn., and Memphis, Tenn. 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.

Cognition was assessed using the 3MSE four times and the 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 researchers used mixed models to assess the connection between SBP levels and 10-year cognitive trajectories, and the impact of race was observed via a race interaction term.

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.

Adjusted differences between white and black participants with SBP levels of 150 mm Hg or higher and the group with levels of 120 mm Hg or lower were -0.05 and -0.08, respectively, for 3MSE (P=.03) and -0.07 and -0.13 for DSST (P=.05).

The researchers concluded that lower targets may offer greater protection for older black adults with hypertension, and urged that future guidelines consider this racial difference when providing recommendations for management of hypertension.

The team also noted that observational studies provide more consistent results with clinical trials when considering important methodological issues such as as limiting sample heterogeneity and accounting for time-varying blood pressures

The main limitations to the study, the researchers said, was the use of observational data without randomization, and the limited number of cognitive tests.