Blood pressure, blood pressure variability and the risk of poststroke dementia

Quantitative analysis of systemic perfusion and cerebral blood flow in the modeling of aging and orthostatic hypotension

Introduction: Orthostatic hypotension (OH) is common among the older population. The mechanism hypothesized by OH as a risk factor for cognitive decline and dementia is repeated transient cerebral blood flow deficiency. However, to our knowledge, quantitative evaluation of cardiac output and cerebral blood flow due to acute blood pressure changes resulting from postural changes is rare. Methods: We report a new fluid-structure interaction model to analyze the quantitative relationship of cerebral blood flow during OH episodes. A device was designed to simulate the aging of blood vessels. Results and Discussion: The results showed that OH was associated with decreased transient cerebral blood flow. With the arterial aging, lesions, the reduction in cerebral blood flow is accelerated. These findings suggest that systolic blood pressure regulation is more strongly associated with cerebral blood flow than diastolic blood pressure, and that more severe OH carries a greater risk of dementia. The model containing multiple risk factors could apply to analyze and predict for individual patients. This study could explain the hypothesis that transient cerebral blood flow deficiency in recurrent OH is associated with cognitive decline and dementia.

Association of Blood Pressure With Brain Ages: A Cohort Study of Gray and White Matter Aging Discrepancy in Mid-to-Older Adults From UK Biobank

BACKGROUND

Gray matter (GM) and white matter (WM) impairments are both associated with raised blood pressure (BP), although whether elevated BP is differentially associated with the GM and WM aging process remains inadequately examined.

METHODS

We included 37 327 participants with diffusion-weighted imaging (DWI) and 39 630 participants with T1-weighted scans from UK Biobank. BP was classified into 4 categories: normal BP, high-normal BP, grade 1, and grade 2 hypertension. Brain age gaps (BAGs) for GM (BAGGM) and WM (BAGWM) were derived from diffusion-weighted imaging and T1 scans separately using 3-dimensional-convolutional neural network deep learning techniques.

RESULTS

There was an increase in both BAGGM and BAGWM with raised BP (P<0.05). BAGWM was significantly larger than BAGGM at high-normal BP (0.195 years older; P=0.006), grade 1 hypertension (0.174 years older; P=0.004), and grade 2 hypertension (0.510 years older; P<0.001), but not for normal BP. Mediation analysis revealed that the association between hypertension and cognitive decline was primarily mediated by WM impairment. Mendelian randomization analysis suggested a causal relationship between hypertension and WM aging acceleration (unstandardized B, 1.780; P=0.016) but not for GM (P>0.05). Sliding-window analysis indicated the association between hypertension and brain aging acceleration was moderated by chronological age, showing stronger correlations in midlife but weaker associations in the older age.

CONCLUSIONS

Compared with GM, WM was more vulnerable to raised BP. Our study provided compelling evidence that concerted efforts should be directed towards WM damage in individuals with hypertension in clinical practice.

P25/CDK5-mediated Tau Hyperphosphorylation in Both Ipsilateral and Contralateral Cerebra Contributes to Cognitive Deficits in Post-stroke Mice

OBJECTIVE

Post-stroke cognitive impairment (PSCI) develops in approximately one-third of stroke survivors and is associated with ingravescence. Nonetheless, the biochemical mechanisms underlying PSCI remain unclear. The study aimed to establish an ischemic mouse model by means of transient unilateral middle cerebral artery occlusions (MCAOs) and to explore the biochemical mechanisms of p25/cyclin-dependent kinase 5 (CDK5)-mediated tau hyperphosphorylation on the PSCI behavior.

METHODS

Cognitive behavior was investigated, followed by the detection of tau hyperphosphorylation, mobilization, activation of kinases and/or inhibition of phosphatases in the lateral and contralateral cerebrum of mice following ischemia in MACO mice. Finally, we treated HEK293/tau cells with oxygen-glucose deprivation (OGD) and a CDK5 inhibitor (Roscovitine) or a GSK3β inhibitor (LiCl) to the roles of CDK5 and GSK3β in mediating ischemia-reperfusion-induced tau phosphorylation.

RESULTS

Ischemia induced cognitive impairments within 2 months, as well as causing tau hyperphosphorylation and its localization to neuronal somata in both ipsilateral and contralateral cerebra. Furthermore, p25 that promotes CDK5 hyperactivation had significantly higher expression in the mice with MCAO than in the shamoperation (control) group, while the expression levels of protein phosphatase 2 (PP2A) and the phosphorylation level at Tyr307 were comparable between the two groups. In addition, the CDK5 inhibitor rescued tau from hyperphosphorylation induced by OGD.

CONCLUSION

These findings demonstrate that upregulation of CDK5 mediates tau hyperphosphorylation and localization in both ipsilateral and contralateral cerebra, contributing to the pathogenesis of PSCI.

The impact of blood pressure variability on cognition: current limitations and new advances

Dementia is the most common neurodegenerative disease in the aging population. Emerging evidence indicates that blood pressure (BP) variability is correlated with cognitive impairment and dementia independent of mean BP levels. The state-of-the-art review summarizes the latest evidence regarding the impact of BP variability on cognition in cognitively intact populations, patients with mild cognitive impairment, and different dementia types, focusing on the important confounding factors and new advances. This review also summarizes the potential mechanisms underlying the relationship between BP variability and cognitive impairment, and dementia, briefly discussing sex differences in the relationship. At last, current limitations and future perspectives are discussed to optimize BP management in preventing cognitive impairment and dementia.

Remote Patient Monitoring of Blood Pressure Is Feasible Poststroke and Can Facilitate Triage of Care

BACKGROUND AND PURPOSE

Strict blood pressure (BP) control is a universally accepted therapeutic intervention in the prevention of secondary stroke, yet this remains difficult when patients return home postinjury. This study aimed to investigate the application of the remote patient monitoring (RPM) of BP in patients after stroke, or who were at immediate risk of stroke, and the subsequent outcomes relating to triage and escalation of care.

METHODS

This was a single-center proof-of-concept study. Participants were patients aged 18 years and older with a diagnosis of stroke or who were at immediate risk of stroke. Patients were enrolled into the precision recovery program (PRP) and asked to assess their BP and heart rate daily and enter values into a MyCap application for the RPM program. These data were reviewed daily by an assigned PRP clinician, and weekly Zoom meetings were held with the patient. Care was triaged and escalated to a physician as indicated.

RESULTS

Twelve patients (5 [42%] female, aged mean [range] 63 [43-84] years) met the inclusion criteria and continued in the program for median (range) 136 (8-227) days. The median (range) number of excursions of BP above limits per participant was 19 (0-79) for systolic and 36 (0-104) for diastolic. A total of 16 triage events (median [range] 1 [0-3]) were initiated for escalation of care.

CONCLUSIONS

This study demonstrated that RPM is feasible in patients poststroke or at immediate risk of stroke, and facilitates the triage of care when BP is elevated above recommended limits.

Systolic blood pressure variability following endovascular thrombectomy and clinical outcome in acute ischemic stroke: A meta-analysis

Blood pressure variability (BPV) has been linked with the outcome of acute ischemic stroke (AIS) after endovascular thrombectomy (EVT). However, the association of the stroke outcome with specific short-term BPV parameters is unclear. We did a systematic literature search for studies published from January 2010 to September 2020. Eligibility criteria included studies with (1) AIS patients treated with EVT with or without thrombolysis; and (2) analysis of the association between short-term systolic BPV parameter and clinical outcomes. Systolic BPV parameters included standard deviation (SD), coefficient of Variation (CoV), successive Variation (SV), and Variation independent of mean. A total of 11 studies were meta-analyzed, comprising 3520 patients who underwent EVT. Lower odds of achieving good functional outcome at 3 months; that is, modified Rankin Scale (mRS) score ≤2 was associated with SD (OR, 0.854; p = .02), CoV (OR, 0.572; p = .04), SV (OR 0.41; p = .00) of systolic blood pressure (SBP). Likewise, higher odds of one-point increase in mRS score was associated with SD (OR 1.42; p = .03), CoV (OR 1.464; p = .00) and SV (OR 2.605; p = .00) of SBP. However, high BPV was not associated with symptomatic intracranial hemorrhage and all-cause mortality at 90 days. The association of BPV and early neurological deterioration was inconclusive. Based on the available studies, short-term systolic BPV is indicative of the clinical outcome of patients following EVT in AIS. Further research should focus on personalized blood pressure management strategies, rather than a one-size-fits-all approach.