Relationships between residual blood pressure variability and cognitive function in the general population of the PAMELA study

Abstract

The present study was aimed at assessing the relationships between absolute and individual residual blood pressure (BP) variability and cognitive function in a general population. This cross‐sectional study evaluated cognitive function using minimental state evaluation (MMSE) in 471 subjects enrolled in the PAMELA study. MMSE was calculated 10 years after initial enrollment of the subjects in the PAMELA study. Measurements included office, home, and 24‐hour ambulatory BP monitoring. BP variability was obtained by calculating: (a) 24‐hour standard deviation (SD) for systolic and diastolic BP and (b) individual residual BP variability. Mean age (±SD) of the subjects enrolled was 63 ± 5.7 years at the initial evaluation, with a 10‐year increase when MMSE was performed. There was no significant difference in BP or heart rate values measured at office, home, or during 24‐h BP monitoring between subjects with MMSE < 24 and those with ≥24. BP variability measured by SBP and DBP SD was also similar between these two groups. However, individual residual BP variability was significantly greater in subjects with lower MMSE and this difference became more pronounced when the study population was divided in three groups according to MMSE score (10‐20, 21‐23, 24‐30). Individual residual SBP and DBP variability gradually decreased with the increase in MMSE score. Our data show that a sensitive parameter for the development of cognitive impairment is not BP or absolute BP variability but rather its short‐term erratic component, which has been previously shown to be an important prognostic marker for organ damage, cardiovascular, and all‐cause mortality.

The circadian blood pressure variability: There is a signal in the noise

“…Ambulatory blood pressure monitoring (ABPM) has been used since the late 60s for estimating BPV and advances in biomedical instrumentation and digital signal processing allied to the continued clinical interest in this subject helped increasing its use . The recent study by Tadic et al highlights this by analyzing ABPM data of the Pressioni Arteriose Monitorate E Loro Associazioni (PAMELA) study to investigate the relationship of cognitive function with blood pressure and BPV in the general population. The cognitive function was assessed using the Mini‐Mental State Examination, with a cut‐off value of <24 points to classify the population as showing worse cognitive function.…”

“…Motivated by the aforementioned study, we herein promote an in‐depth discussion of the methodological aspects for estimating the individual residual variability. First, the population‐average of ABPM—aka the coherent average—increases the signal‐to‐noise ratio of time‐series that are synchronized, time‐invariant, and corrupted with uncorrelated white noise.…”

“…Third, the linear curve‐fitting of the Fast Fourier Transform frequency components leads to a perfect oscillatory pattern that just simplifies the actual ABPM. Finally, the individual residual variability is estimated after removal of only two frequency components ascribed to day‐night and preprandial‐postprandial oscillations, accounting for ~50% of the variance of the systolic and diastolic blood pressures SD in Tadic et al’s study …”

“…BPV can be estimated by a variety of parameters, apparently, not all parameters hold clinical relevance for predicting morbidity and mortality from CVD . Tadic et al discussed that “fast” blood pressure changes might explain the individual residual variability that is neither too low (day‐night and preprandial‐postprandial oscillations) or too fast (if manual edition and device's precision are considered the true uncorrelated white noise). In this sense, their study provides very interesting supporting evidence on the use of the individual residual variability as a marker of cognitive function in the general population.…”

“…Tadic et al discussed that “fast” blood pressure changes might explain the individual residual variability that is neither too low (day‐night and preprandial‐postprandial oscillations) or too fast (if manual edition and device's precision are considered the true uncorrelated white noise). In this sense, their study provides very interesting supporting evidence on the use of the individual residual variability as a marker of cognitive function in the general population. Herein we stress that further research is warranted to unveil other physiologic, behavioral, and/or environmental events that play an important role in explaining the relationship between cognitive function and BPV.…”