Cumulative mean systolic blood pressure was associated with those faster declines in memory which were significantly more common in black individuals than white individuals.
Deborah A. Levine, MD, MPH
Individual participant data pooled from 5 study cohorts showed a significantly faster decline in cognition in black participants compared with white, suggesting that black individuals’ higher cumulative blood pressure (BP) levels may contribute to racial differences in later-life cognitive decline.
Results showed that black individuals had significantly faster declines in global cognition (−0.03 points per year faster [95% CI, −0.05 to −0.01]; P = .004) and memory (−0.08 points per year faster [95% CI, −0.11 to −0.06]; P <.001) but significantly slower declines in executive function (0.09 points per year slower [95% CI, 0.08—0.10]; P <.001), compared to white individuals.
Researchers, including Deborah A. Levine, MD, MPH, lead investigator, and associate professor of chronic disease care, University of Michigan, and colleagues, gathered data from studies between 1971 and 2017 that had repeated measures of BP and cognition, including the Atherosclerosis Risk in Communities Study (ARIC), Coronary Artery Risk Development in Young Adults Study (CARDIA), Cardiovascular Health Study (CHS), Framingham Offspring Study (FOS), and Northern Manhattan Study (NOMAS).
The study sample included 19,378 participants (10,724 [55.3%] female; 15,526 [80.1%] white) with a median (interquartile range [IQR]) follow-up of 12.4 (IQR, 5.9—21.0) years. The median (IQR) number of global cognition and memory assessments was 2 (IQR, 2–4) for black individuals and 4 (IQR, 2–7) for white individuals.
Each study had at least 2 measurements of cognition and 1 of BP at or before the first cognition measurement. Participants who self-reported a race other than black or white, including those who reported Hispanic ethnicity in NOMAS, were excluded from the analysis. Systolic BP (SBP) was measured at in-person visits and was summarized as the time-dependent cumulative mean of all BP’s before each cognitive measurement. SBP was used instead of diastolic BP because it has a higher tendency to predict BP-related outcomes.
Primary outcome of the study was change in global cognition while secondary outcomes included change in memory and executive function. Researchers used t scores (mean [standard deviation (SD)], 50 ), with a 1-point difference represented a 0.1—SD difference in cognition, as a way to standardize outcomes.
The study included 3 models to help determine statistical analysis. Model A measured black race multiplied by follow-up time interaction term to estimate differences between black and white individuals in cognitive decline. Model B then added SBP and an SBP multiplied by follow-up interaction term to model A to examine whether time-dependent cumulative mean SBP explained the racial differences. Lastly, researchers added hypertension treatment and a hypertension treatment at first cognitive assessment multiplied by follow-up time interaction term to model B to investigate whether hypertension treatment explained the racial differences in cognitive decline.
In addition to previously stated quicker declines in global cognition in black individuals, researchers found an association between cumulative SBP and faster declines in global cognition (—0.018 points per year points per year faster per each 10-mm Hg increase [95% CI, –0.023 to –0.014]; P <.001).
Faster declines in memory were significantly more present in black individuals than white individuals (adjusted difference in slope between black and white individuals: −0.08 points per year faster [95% CI, −0.11 to −0.06]; P <.001). Additionally, cumulative mean SBP was associated with those faster declines in memory (−0.028 points per year faster per each 10—mm Hg increase [95% CI, −0.035 to −0.021]; P <.001).
“Although prominent organizations recommend improved BP treatment and control in black individuals to reduce cardiovascular disease risk and disparities between black and white individuals in cardiovascular outcomes, our results suggest that improved BP control may also reduce black individuals’ risk of accelerated cognitive decline and racial disparities in cognitive outcomes,” Levine and colleagues concluded.
Levine DA, Gross AL, Briceno EM, et al. Association between blood pressure and later-life cognition among black and white individuals. JAMA Neurol. Published online April 13, 2020. doi: 10.1001/jamaneurol.2020.0568