By Will Boggs MD
NEW YORK (Reuters Health) - Lower systolic blood pressure (SBP) targets are not associated with worsening cognitive outcomes, according to findings from the Health Aging and the Body Composition (Health ABC) study.
"One should consider that higher-risk populations such as African Americans or seniors with hypertension may gain more by lowering blood pressure to below 140 mm Hg levels,” Dr. Ihab Hajjar from the Emory School of Medicine, Atlanta, Georgia, told Reuters Health by email.
The Eighth Joint National Committee (JNC-8) recommends treating older adults with SBP of 150 mm Hg or higher, whereas results from the recent SPRINT study support a target SBP <120 mm Hg.
Dr. Hajjar and colleagues investigated the cognitive impact of different SBP levels among 1657 older adults in the Health ABC study receiving treatment for hypertension. They also examined differences by race.
At baseline, SBP was 120 mm Hg or lower in 18.5% of participants, 121-139 mm Hg in 37.8%, 140-149 mm Hg in 15.9%, and 150 mm Hg or higher in 27.7%, according to the August 21 JAMA Neurology online report.
During 10 years of follow-up, cognitive scores declined most in patients with SBP of 150 mm Hg or higher, and they declined least in patients with SBP of 120 mm Hg or lower.
With respect to cognitive performance, lower SBP benefited black participants more than white participants.
“Although we found statistical significance in these analyses, the magnitude of the change over the 10-year period was small,” the researchers note. “Nevertheless, we did not observe an association between lower targets and cognition that was significantly detrimental. This analysis, which was specifically conducted for older adults receiving treatment for hypertension, provides the additional suggestion that the potential for a detrimental cognitive outcome of a target SBP lower than 140 or 120 mm Hg is not substantiated with appropriately designed analyses of observational data.”
“The findings of the present study suggest that a lower systolic blood pressure target for black patients is linked to greater cognitive benefit,” they add. “Future recommendations for the management of hypertension and cognitive outcomes need to take this racial disparity into consideration.”
“The observational nature of this analysis does not offer robust evidence for changing guidelines,” Dr. Hajjar said by email. “However, it does offer some pause for the change in the JNC guidelines to allow treated hypertensive older adults (older than 60) to have SBP above 140 mm Hg.”
Dr. Rebecca F. Gottesman from Johns Hopkins University School of Medicine, Baltimore, who wrote a related editorial, told Reuters Health by email, "The finding that lower blood pressure appeared to be especially protective in black as compared to white participants is not extremely surprising, but it is something that hasn’t been shown before. This is important, because it might point to an opportunity for reducing disparities in dementia rates, if in further studies it is found that blood-pressure reduction has an even greater role in preventing dementia in blacks versus whites.”
“This study emphasizes that blood pressure control may not only be important for cardiovascular outcomes and stroke, but also for cognition,” she concluded. “Previous studies have emphasized that midlife blood pressure is especially important for cognitive outcomes, but this study suggests that blood pressure in later life may also be important for later-life cognitive performance.”
Dr. Gottesman added that because the study was observational, its findings must be interpreted cautiously. “People who take their medicines and are able to get their blood pressure under adequate control are likely quite different, even in ways we can’t measure that well, from people who do not have well-controlled blood pressure. Thus, we might be seeing an effect on cognition because of other differences in these groups (in access to medical care, lifestyle choices, or other medications being taken), as opposed to from the medications themselves. It is likely, however, that the apparent benefit for cognition in well-controlled blood pressure is due to some combination of those two factors - a true biological benefit, plus this potential bias because of differences in who is on medications in the first place.”
Dr. Eric McDade from Washington University at St. Louis, in Missouri, told Reuters Health by email, "In general, this study would suggest that in the elderly, attempts should be made to prevent hypertension in the first place, but in those with established hypertension, treating them aggressively to maintain a blood pressure (at levels specified) in the JNC-7 guidelines (<140 mm Hg) should be considered for the maintenance of cognitive function.”
“Furthermore, for African Americans it is possible that a more aggressive target, i.e., SPRINT trial, may provide more benefit for cognition than in non-African Americans,” he said.
McDade also noted that the relative decline within 10 years between patients with the highest versus the lowest blood pressure was relatively small. “So before making too strong a claim,” he said, “it would be important to note the impact on lowering blood pressure aggressively,” such as a greater incidence of falls and higher costs, given the modest cognitive benefits.
“The goal should be to encourage behaviors that keep blood pressure low (lifestyle factors for instance), and once blood pressure begins to increase it should be addressed relatively aggressively at all stages of life,” Dr. McDade said. “This study further reinforces the need to consider cognitive outcomes in studies that assess cardiovascular risk factors and outcomes . . . such as stroke or heart attack.”
“With the decrease in cardiovascular morbidity and increasing lifespan, it is increasingly important to understand risk factors for dementia,” he said. “The strongest risk factor of dementia is age, so if we are able to prolong lifespan only to increase the amount of people that develop dementia, this is not the best outcome.”
Dr. Devan Kansagara from Oregon Health and Science University, Portland, told Reuters Health by email, "Whether or not lower treatment targets actually reduce the rate of decline in cognitive function in a clinically meaningful way over time is not clear. This study found statistically significant differences in the rate of cognitive decline, but . . . it is not clear these differences were large enough to be noticed by patients or family.”
Kansagara also noted the limitations of the observational study. “It is impossible to know whether treating patients more aggressively resulted in a slower decline of cognitive function,” he said, “or whether patients/physicians may have decided against titrating blood pressure medications because of worsening cognitive function.”
“While there are a number of factors to consider in choice of treatment target, fear of worsening patients' cognitive function should probably not be used as a rationale to choose higher treatment targets,” he said.
SOURCES: http://bit.ly/2x5QVeX and http://bit.ly/2v7POtA
JAMA Neurol 2017.
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