Lower BP Targets Preserve Cognition in Older Adults

Nancy A. Melville

August 30, 2017

Lower targets for systolic blood pressure (SBP) in older individuals appear to preserve cognitive function, with the effect significantly stronger in black patients, new research shows.

"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. The lower targets may offer greater protection for older black adults with hypertension," the investigators, led by Ihab Hajjar, MD, Emory School of Medicine, Atlanta, Georgia, write.

The study was published online August 21 in JAMA Neurology.

Effect by Race

Previous hypertension guidelines from the Seventh Joint National Committee (JNC-7) recommended treatment for older adults at a cutoff of 140 mm Hg. However, the eighth committee (JNC-8) raised the target in 2014 to 150 mm Hg for individuals aged 60 years and older because of concern that the lower cutoff may have adverse effects, including cognitive decline, falls, and mortality.

Meanwhile, clinical trials have shown benefits in favor of the lower target, with the Systolic Blood Pressure Intervention Trial (SPRINT) in 2015 showing a lower risk for cardiovascular disease without the increased risk for falls with the more aggressive 120–mm Hg target in individuals under, as well as over, age 75 years.

However, findings on cognitive outcomes from that study have not yet been reported.

To examine this issue, investigators evaluated data from 1657 cognitively intact older adults receiving treatment for hypertension who participated in the Health Aging and Body Composition (Health ABC) study and were studied from 1997 to 2007. Data were analyzed from October 2016 to January 2017.

Of this cohort, 908 patients were women and 784 were black. The mean age was 74 years, and all patients were cognitively intact at baseline.

Cognition was assessed by using the Modified Mini-Mental State Examination (3MSE) four times and the Digit Symbol Substitution Test (DSST) five times during the study.  Results showed a differential decrease in 3MSE and DSST scores by SBP. The greatest decrease was in the group that had SBP of 150 mm Hg or higher.

The adjusted decrease was 3.7 points for 3MSE and 6.2 points for DSST. The lowest decrease was in the group with SBP of 120 mm Hg or lower, with an adjusted decrease of 3.0 for 3MSE and 5.0 for DSST (P < .001 for both), the investigators report.

Patients with SBP of 150 mm Hg or higher were more likely to be black (54%). The investigators found that compared with white patients, black patients showed significantly greater differences in cognition based on SBP.

Adjusted differences between the group with SBP of 150 mm Hg or higher and the group with SBP of 120 mm Hg or lower were –0.05 in white patients and –0.08 in black patients on the 3MSE assessment (P = .03) and –0.07 in white patients and –0.13 in black patients for DSST (P = .05).

The authors note that the findings are consistent with those of a recent study of patients in the National Institutes of Health–National Institute on Aging Alzheimer Disease Centers, which also showed greater declines in cognition in people with SBP of 150 mm Hg or higher over a 3-year follow-up period compared with those with lower SBP targets.

"The present study extends that to a longer follow-up and demonstrates the importance of lower treatment targets in an even older segment of the population. …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 health care," they write.

The findings regarding the greater poorer cognitive function in blacks with SBP of 150 mm Hg and higher are also important, considering that  no hypertension guidelines and blood pressure targets take patient race into account. It is well known that blacks have a higher prevalence of hypertension, resulting in greater vascular damage and morbidity.

In the key source of evidence for the JNC-8 guidelines, the Hypertension in the Very Elderly Trial (HYVET), blacks were underrepresented, the authors note, and evidence from a recent study supports the current findings. Those results show higher reports of cognitive symptoms associated with hypertension in blacks and a link between those symptoms and increased mortality.

Dr Hajjar noted that a host of other morbidities associated with hypertension could also be addressed by improved hypertension control in blacks.

"The negative health effects of higher blood pressure are more prevalent in blacks, especially related to kidney disease, stroke, and cardiovascular health," he told Medscape Medical News.

"Therefore, it is conceivable that lowering blood pressure in this population would have a far greater impact than other groups for the cognitive effects as well."

Unanswered Questions

In an accompanying editorial, Rebecca Gottesman, MD, PhD, Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, Maryland, notes that although the study's findings add to evidence regarding lower SBP targets for older patients, there are several unanswered questions.

"These 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, these 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," she writes.  

Various other factors not included in the adjustments could have had a beneficial effect on patients' cognition. Factors such as adherence or access to medical care may be more common in the lower SBP groups. For instance, the group with SBP under 120 mm Hg had the highest rates of postsecondary education and the lowest rates of low household income.

In addition, she noted that during the 10-year study, approximately 25% of the population was lost to follow-up, and this group could include many with poor cognitive trajectories.

"Because cognitive decline is a major risk factor for attrition (owing to death or loss to follow-up), as is hypertension, it is likely that the individuals at highest risk for poor cognitive outcomes may have not completed the 10-year follow- up, thus leading to a dilution of the true association between hypertension and cognitive decline," Dr Gottesman writes.

She added that the finding that lower SBP was particularly protective for cognition in black patients is important given the known higher rates of dementia in this population and may have important implications for their care.

"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," Dr Gottesman writes.

The Health Aging and Body Composition study was funded by the National Institute on Aging, and the National Institute of Nursing Research. The research was also funded in part by the Intramural Research Program of the National Institutes of Health, National Institute on Aging. The authors have disclosed no relevant financial relationships. Dr Gottesman is an associate editor for Neurology.

JAMA Neurology. Published online August 21, 2017. Abstract, Editorial

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