Variabilitat de la pressió arterial com a factor associat a deteriorament cognitiu i atròfia cerebral

Abstract

Hypertension is a risk factor for cognitive impairment (CI). Traditionally, this risk has been attributed to mean blood pressure (BP). However, BP blood pressure levels exhibit a great variability over time. Blood pressure variability (BPV) can be assessed in the short term (within 24 hours) using ambulatory blood pressure monitoring (ABPM) or in the long term through BP measurements blood pressure measurements from different visits separated in time. Recently, BPV has been associated with a higher risk of CI and cerebral atrophy, regardless of the mean arterial pressure levels. Several indices have been proposed to measure BPV, such as the standard deviation (SD), the coefficient of variation (CV) and the Average Real Variability (ARV). The relationship between long-term BPV and CI is well established; however, studies assessing short-term BPV and cognition show conflicting results. Furthermore, the association between both types of VPA and mild cognitive impairment (MCI), a cognitive state that precedes dementia, has been assessed in few studies and has not been performed prospectively. The aim of this Thesis was to evaluate short-term and long-term BPV in a cohort of hypertensive patients and prospectively determine its association with cognitive decline and with cognitive changes between normal cognition states and MCI after four years of follow-up. The association of BPV with medial temporal cerebral atrophy (MTA) on cranial MRI was also investigated. 361 hypertensive patients were evaluated in two visits separated four years between them. A cognitive assessment, cranial MRI, and ABPM (used to calculate short-term VPA) were performed at each visit. BP determinations measured in Primary Care between both visits were also collected to calculate long-term BPV. In both visits, the Dementia Rating Scale-second edition (DRS-2) was performed and each subject was classified in cognitive normal state or MCI. Incident MCI patients between both visits were collected. The MTA was evaluated using the visual Scheltens scale. For long-term BPV, elevations of SD (OR 1.14,IC 95%:1.01-1.29), CV CV (OR 1.19,IC 95%:1.02-1.40) and ARV (OR 1.11,IC 95%:1.01-1.22) of systolic BP exhibited a higher risk of incident MCI, independent of the cumulative BP values. The DRS-2 scale Z score was negatively related to systolic CV (B -0.03,IC 95% -0.06 a -0.01) and ARV (B -0.03,IC 95% -0.06 a -0.01). The executive function subscale was also associated with systolic SD (B -0.02,IC 95% -0.04 a 0.00). MTA was associated with higher quartiles of the systolic SD (OR 2.13,IC 95%:1.01-4.48) and CV (OR 2.35,IC 95%:1.14-4.82). Short-term BPV was not related to a higher risk of MCI. A positive association between daytime systolic ARV and DRS-2 total Z scores was detected (B 0.05, IC 95%:0.03-0.09). There were no associations between short-term BPV and MTA. In conclusion, several indices of long-term BPV were associated with the risk of incident MCI, with decreased DRS-2 scores and with the presence of brain MTA, regardless of blood pressure levels. On the other hand, these associations were not found for short-term BPV. In this way, long-term BPV could be useful as a possible predictor of MCI and cognitive decline and could be associated with MTA.