1,721,251 research outputs found
Antihypertensive drug class effects on inter-individual blood pressure variability and the associated risk of stroke
Full text linkVisit-to-visit variability in systolic blood pressure (SBP) predicts the subsequent risk of stroke, independent of mean SBP. It was reduced by amlodipine and increased by atenolol in the ASCOT-BPLA and MRC randomized controlled trials (RCTs), explaining the difference in risk of stroke between treatment groups that was not explained by mean SBP. Therefore, I performed a series of systematic reviews to examine the effects of all antihypertensive drugs in RCTs and how these effects relate to the risk of stroke.Cochrane and Medline databases were searched for systematic reviews and RCTs of antihypertensive drugs. Baseline and follow-up data for mean (SD) SBP and DBP were extracted. Differences in inter-individual variance (SD2) in BP were expressed as a ratio (VR) and risk of stroke was compared by odds ratios (OR). Estimates were pooled by random-effects meta-analysis.Compared to all other drugs, variability in SBP was reduced by randomization to calcium channel blockers (CCB: VR=0.81 95%CI 0.76-0.86, p<0.0001) and non-loop diuretics (0.87, 0.79-0.96, p=0.007), and increased by ACE-inhibitors (1.08, 1.02-1.15, p=0.008), angiotensin-receptor blockers (1.16, 1.07-1.25, p=0.0002) and beta-blockers (1.17, 1.07-1.28, p=0.0007). Across all trials, effects of treatment on VR SBP (r²=0.372, p=0.0006) and on mean SBP (r²=0.328, p=0.0015) explained effects on stroke risk. Randomization to a CCB reduced the subsequent risk of stroke (OR=0.88, 0.83-0.94, p=0.0002). These effects on VR-SBP were dose-dependent and persisted when drugs were used in combination. Randomisation to a non-selective beta-blocker increased VR more than β1-selective agents (VR=1.23, 1.03-1.47, p=0.03), probably explaining the markedly increased risk of stroke in patients randomized to propranolol in the MRC-mild trial. Effects were not explained by changes in the incidence of new-onset atrial fibrillation.Effects of antihypertensive drug classes on visit-to-visit variability in SBP explain effects of these drugs on the risk of stroke. CCBs are indicated for patients at increased risk of stroke due to episodic or variable systolic hypertension, but higher doses are required either as monotherapy or in combinations. Non-loop diuretics have smaller benefits, but beta-blockers are associated with increased variability in SBP and risk of stroke, particularly due to non-selective beta-blockers. These should be avoided in patients at an increased risk of stroke
Prognostic Significance of Blood Pressure Variability on Beat-to-Beat Monitoring After Transient Ischemic Attack and Stroke
Full text link
Background and Purpose—
Visit-to-visit and day-to-day blood pressure (BP) variability (BPV) predict an increased risk of cardiovascular events but only reflect 1 form of BPV. Beat-to-beat BPV can be rapidly assessed and might also be predictive.
Methods—
In consecutive patients within 6 weeks of transient ischemic attack or nondisabling stroke (Oxford Vascular Study), BPV (coefficient of variation) was measured beat-to-beat for 5 minutes (Finometer), day-to-day for 1 week on home monitoring (3 readings, 3× daily), and on awake ambulatory BP monitoring. BPV after 1-month standard treatment was related (Cox proportional hazards) to recurrent stroke and cardiovascular events for 2 to 5 years, adjusted for mean systolic BP.
Results—
Among 520 patients, 26 had inadequate beat-to-beat recordings, and 22 patients were in atrial fibrillation. Four hundred five patients had all forms of monitoring. Beat-to-beat BPV predicted recurrent stroke and cardiovascular events independently of mean systolic BP (hazard ratio per group SD, stroke: 1.47 [1.12–1.91];
P
=0.005; cardiovascular events: 1.41 [1.08–1.83];
P
=0.01), including after adjustment for age and sex (stroke: 1.47 [1.12–1.92];
P
=0.005) and all risk factors (1.40 [1.00–1.94];
P
=0.047). Day-to-day BPV was less strongly associated with stroke (adjusted hazard ratio, 1.29 [0.97–1.71];
P
=0.08) but similarly with cardiovascular events (1.41 [1.09–1.83];
P
=0.009). BPV on awake ambulatory BP monitoring was nonpredictive (stroke: 0.89 [0.59–1.35];
P
=0.59; cardiovascular events: 1.08 [0.77–1.52];
P
=0.65). Despite a weak correlation (
r
=0.119;
P
=0.02), beat-to-beat BPV was associated with risk of recurrent stroke independently of day-to-day BPV (1.41 [1.05–1.90];
P
=0.02).
Conclusions—
Beat-to-beat BPV predicted recurrent stroke and cardiovascular events, independently of mean systolic BP and risk factors but short-term BPV on ambulatory BP monitoring did not. Beat-to-beat BPV may be a useful additional marker of cardiovascular risk.
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White Matter Imaging Correlates of Early Cognitive Impairment Detected by the Montreal Cognitive Assessment after Transient Ischemic Attack and Minor Stroke
Full text linkBACKGROUND AND PURPOSE: Among screening tools for cognitive impairment in large cohorts, the Montreal Cognitive assessment (MoCA) appears to be more sensitive to early cognitive impairment than the Mini-Mental State Examination (MMSE), particularly after transient ischemic attack (TIA) or minor stroke. We reasoned that if MoCA-detected early cognitive impairment is pathologically significant, then it should be specifically associated with the presence of white matter hyperintensities (WMH) and reduced fractional anisotropy (FA) on MRI.
METHODS: Consecutive eligible patients with TIA or minor stroke (Oxford Vascular Study) underwent MRI and cognitive assessment. We correlated MoCA and MMSE scores with WMH and FA, then specifically studied patients with low MoCA and normal MMSE.
RESULTS: Among 400 patients, MoCA and MMSE scores were significantly correlated (all p<0.001) with WMH volumes (rMoCA=-0.336, rMMSE=-0.297) and FA (rMoCA=0.409, rMMSE=0.369), and -on voxel-wise analyses- with WMH in frontal white matter and reduced FA in almost all white matter tracts. However, only the MoCA was independently correlated with WMH volumes (r=-0.183, p<0.001), average FA values (r=0.218, p<0.001), and voxel-wise reduced FA in anterior tracts after controlling for the MMSE. In addition, patients with low MoCA but normal MMSE (N=57) had higher WMH volumes (t=3.1,p=0.002), lower average FA (t=-4.0,p<0.001), and lower voxel-wise FA in almost all white matter tracts than those with normal MoCA and MMSE (N=238).
CONCLUSIONS: In patients with TIA or minor stroke, early cognitive impairment detected with the MoCA but not with the MMSE was independently associated with white matter damage on MRI, particularly reduced FA
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Age and sex-specific associations of carotid pulsatility with small vessel disease burden in transient ischemic attack and ischemic stroke
Full text linkBackground Although large artery stiffness has been implicated in the pathogenesis of cerebral small vessel disease, whether carotid pulsatility, a convenient surrogate marker of arterial stiffness, is similarly associated with global burden of small vessel disease is unknown.Aims To determine the age and sex-specific associations of carotid pulsatility with global burden of small vessel disease.Methods We studied consecutive patients with transient ischemic attack or non-disabling ischemic stroke from the Oxford Vascular Study who had a brain MRI and carotid duplex ultrasound during 2002-2014. We determined clinical correlates of common carotid artery (CCA) and internal carotid artery (ICA) pulsatility index (PI) and their associations with the total small vessel disease score on MRI, stratified by age (median=72).Results In 587 patients, correlates of CCA and ICA-PI were both independently associated with age, diabetes, and premorbid mean pulse pressure after adjustment for age, sex, and cardiovascular risk factors (all p0.05). No associations between CCA-PI with small vessel disease score were noted at any age. In 94 consecutive patients who also received transcranial Doppler ultrasound, strong associations between middle cerebral artery (MCA)-PI and an increasing small vessel disease score were noted (unadjusted OR-MCA: 4.26, 1.45-12.55, p=0.009; ICA: 2.37, 0.81-6.87, p=0.11; CCA: 1.33, 0.45-3.96, p=0.61).Conclusions ICA and MCA-PI are associated with global small vessel disease burden, especially in individuals aged<70 and may be causally related
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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