Dynamical Dark Energy simulations: high accuracy Power Spectra at high redshift

Accurate predictions on non--linear power spectra, at various redshift z, will be a basic tool to interpret cosmological data from next generation mass probes, so obtaining key information on Dark Energy nature. This calls for high precision simulations, covering the whole functional space of w(z) state equations and taking also into account the admitted ranges of other cosmological parameters; surely a difficult task. A procedure was however suggested, able to match the spectra at z=0, up to k~3, hMpc^{-1}, in cosmologies with an (almost) arbitrary w(z), by making recourse to the results of N-body simulations with w = const. In this paper we extend such procedure to high redshift and test our approach through a series of N-body gravitational simulations of various models, including a model closely fitting WMAP5 and complementary data. Our approach detects w= const. models, whose spectra meet the requirement within 1% at z=0 and perform even better at higher redshift, where they are close to a permil precision. Available Halofit expressions, extended to (constant) w \neq -1 are unfortunately unsuitable to fit the spectra of the physical models considered here. Their extension to cover the desired range should be however feasible, and this will enable us to match spectra from any DE state equation.Comment: method definitely improved in semplicity and efficacy,accepted for publication on JCA

Serum magnesium and calcium levels in relation to ischemic stroke : Mendelian randomization study

ObjectiveTo determine whether serum magnesium and calcium concentrations are causally associated with ischemic stroke or any of its subtypes using the mendelian randomization approach.MethodsAnalyses were conducted using summary statistics data for 13 single-nucleotide polymorphisms robustly associated with serum magnesium (n = 6) or serum calcium (n = 7) concentrations. The corresponding data for ischemic stroke were obtained from the MEGASTROKE consortium (34,217 cases and 404,630 noncases).ResultsIn standard mendelian randomization analysis, the odds ratios for each 0.1 mmol/L (about 1 SD) increase in genetically predicted serum magnesium concentrations were 0.78 (95% confidence interval [CI] 0.69-0.89; p = 1.3 7 10-4) for all ischemic stroke, 0.63 (95% CI 0.50-0.80; p = 1.6 7 10-4) for cardioembolic stroke, and 0.60 (95% CI 0.44-0.82; p = 0.001) for large artery stroke; there was no association with small vessel stroke (odds ratio 0.90, 95% CI 0.67-1.20; p = 0.46). Only the association with cardioembolic stroke was robust in sensitivity analyses. There was no association of genetically predicted serum calcium concentrations with all ischemic stroke (per 0.5 mg/dL [about 1 SD] increase in serum calcium: odds ratio 1.03, 95% CI 0.88-1.21) or with any subtype.ConclusionsThis study found that genetically higher serum magnesium concentrations are associated with a reduced risk of cardioembolic stroke but found no significant association of genetically higher serum calcium concentrations with any ischemic stroke subtype

Stroke services: a global perspective

No abstract available

Stroke services: a global perspective

No abstract available

Does admission to hospital improve the outcome for stroke patients?

Objectives: to identify the factors associated with hospital admission and the differences in management and outcome of stroke patients between hospital and home. Design: a prospective community stroke register (1995–8) with multiple notification sources. Setting: an inner city multi‐ethnic population of 234 533 in South London, UK. Participants: 975 subjects with first in a lifetime strokes, whether or not they were admitted to hospital. Patients dying suddenly and those already hospitalized at the time of stroke were excluded. Main outcome measures: factors associated with hospital admission; differences in management in the acute phase of stroke; mortality and dependency assessed by the Barthel index 3 months post‐stroke. Results: 812 patients were admitted to hospital for stroke; 163 were managed in the community. Factors independently associated with hospital admission included stroke severity, pre‐stroke independence, atrial fibrillation, having an intracranial haemorrhage and having a non‐lacunar infarction. Computed tomography scan rates were higher in admitted (78%) than non‐admitted patients (63%; P=0.001). By 3 months, 285 (35%) of the admitted patients had died compared with 13 (8%) of non‐admitted patients (P<0.001). Of the admitted patients, 241 (47%) had a Barthel index ≥18 compared with 106 (72%) of those who were not admitted (P<0.001). After adjusting for case‐mix variables, the odds ratios for death and dependency (Barthel index<18) in admitted and non‐admitted patients were 2.21 (0.96–5.12) and 2.39 (1.35–4.22) respectively. Conclusion: patients with clinical indicators for a more severe stroke were more likely to be admitted to hospital. Hospitalized stroke patients may have poorer survival and disability rates than those who remain at home, even after adjustment for case mix. There may be some aspects of acute hospital care that may be detrimental to outcome in certain groups of stroke patients. This requires further investigation

Behavioral risk factor prevalence and lifestyle change after stroke : a prospective study

<p>Background and Purpose — Stroke patients have a 15-fold increased risk of recurrent stroke, and those with ≥1 risk factor have a further increased risk of recurrence. Previous work found management of physiological risk factors after stroke to be unsatisfactory, but there is little information on behavioral risks within the stroke population. This study estimates behavioral risk factor prevalence after stroke and explores lifestyle change.</p> <p>Methods — The study used data from the population-based South London Stroke Register, collected prospectively between 1995 and 1998. Main measures included smoking status, alcohol use, and obesity. Logistic regression was used to determine sociodemographic differences in these measures.</p> <p>Results — At 1 year after stroke, 22% of patients still smoked, 36% of patients were obese, and 4% drank excessively. Younger patients, whites, and men were more likely to smoke, and younger whites were more likely to drink excessively. Women and nonwhites were more likely to be obese. Those living in hospital, nursing home, or residential care and nonwhites were more likely to give up smoking, but there were no other associations between lifestyle change and the sociodemographic characteristics of patients.</p> <p>Conclusions — Different behavioral risk factors were associated with specific sociodemographic groups within the stroke population. After stroke, high-risk groups should continue to be targeted to prevent stroke recurrence. However, the relationship between sociodemographic characteristics and lifestyle change remains unclear; more research is needed into the process of change to find out how best to intervene to improve secondary prevention.</p&gt

A comparison of characteristics and resource use between in hospital stroke and admitted stroke patients

Background: Although in-hospital stroke is not a common occurrence, it is important to identify what components of stroke care these patients receive. The aims of this study were to estimate the clinical characteristics, process of stroke care, and mortality in patients admitted to hospital with stroke compared with patients with in-hospital strokes. Methods: Data from a community-based stroke register (1995-2004) in an inner city multiethnic population of 271,817 in South London, United Kingdom, were analyzed. Results: From a total of 2402 patients, 291 (12.1%) had in-hospital strokes. Patients with in-hospital strokes were more likely to be incontinent, be dysphagic, have a motor deficit, and have a low level of consciousness (P < .001) compared with admitted patients with stroke. Brain imaging was carried out more frequently in admitted patients with stroke (P < .001). Access to stroke unit care was higher in admitted patients with stroke (P < .001). In-hospital patients with stroke had a longer mean length of stay (55.9 days) compared with admitted patients with stroke (37.9 days, P < .001). There were no significant differences between the groups for receipt of physiotherapy or occupational therapy after discharge (P = .232) or receipt of speech and language therapy (P = .345). After adjustment of case mix variables, in-hospital patients with stroke were less likely to undergo imaging (odds ratio [OR] = 0.54, 95% confidence interval [CI] = 0.33-0.89, P = .015). In-hospital patients with stroke were less likely to be treated in a stroke unit (OR = 0.33, 95% CI = 0.22-0.50, P < .001) and prescribed antiplatelet therapy at 3 months (OR = 0.51, 95% CI = 0.30-0.88, P = .015). By 3 months, in-hospital patients with stroke were more likely to have died (P < .001), although this was not significant after case mix adjustment (OR = 1.39, 95% CI = 0.90-2.15, P = .135). Conclusion: This study demonstrated that in-hospital patients with stroke had worse stroke severity, and poorer access to a number of components of stroke care compared with admitted patients with stroke. All hospitals should include, in their stroke policies and guidelines, evidence-based pathways that prioritize the needs of patients who have a stroke while in hospital.Peer reviewe

Intraobserver and interobserver agreement in visual inspection for xanthochromia: implications for subarachnoid hemorrhage diagnosis, computed tomography validation studies, and the Walton rule

Background: Visual inspection for xanthochromia is used to diagnose subarachnoid hemorrhage (SAH), to validate computed tomography subarachnoid hemorrhage diagnosis and was used to determine the Walton rule. No study has assessed the reliability of xanthochromia.\ud \ud Objective: To determine intraobserver and interobserver xanthochromia agreement.\ud \ud Methods: Mock cerebrospinal fluid samples contained increasing concentrations of human oxyhemoglobin, bilirubin, and albumin. Non-color-blind observers randomly assessed samples against a white background twice under significantly differing illumination. Specimens were recorded as red, orange, yellow, or clear.\ud \ud Results: Results were obtained for 26 observers (11 male, 15 female observers). We found that 19.2% of samples were misclassified: red, 11.7%; orange, 28.5%; yellow, 29.6%; and clear, 22.1% (χ = 213.2; P < .001). Of the yellow misclassifications, 88% were misclassified as clear. Female observers correctly classified samples significantly more frequently than male observers (P = .03). Intraobserver agreement differed significantly from expected for both male (χ = 105.6; P < .001) and female (χ = 99.9; P < .001) observers regardless of illumination. Interobserver agreement was poor regardless of sex (χ for male observers = 176.96, P < .001; χ for female observers = 182.69, P < .001) or illumination (χ for bright = 125.64, P < .001; χ for dark = 148.48, P < .001). Overall, there was 75% agreement in 46% of the tests and 90% agreement in only 36% of the tests.\ud \ud Conclusion: This simple laboratory study would be expected to maximize agreement relative to clinical practice. Although non-color-blind female observers significantly outperformed non-color-blind male observers, both intraobserver agreement and interobserver agreement for xanthochromia were prohibitively poor regardless of sex or illumination. Yellow was most frequently misclassified, 88% as clear (ie, true positives were commuted to false negatives). Xanthochromia is therefore highly unreliable for subarachnoid hemorrhage diagnosis and computed tomography validation. The Walton rule requires urgent clinical revalidation

Antithrombotic and antihypertensive management 3 months after ischemic stroke : a prospective study in an inner city population

&lt;p&gt;Background and Purpose — We sought to examine the frequency, predictors, and effects of nontreatment with antithrombotic and antihypertensive therapies 3 months after ischemic stroke.&lt;/p&gt; &lt;p&gt;Methods — The population-based South London Community Stroke Register prospectively collected data on first-in-a-lifetime strokes between 1995 and 1997. Among patients registered with ischemic stroke, treatment status with antithrombotic and antihypertensive therapies was examined 3 months after the event.&lt;/p&gt; &lt;p&gt;Results — In a cohort of 457 patients with ischemic stroke, 393 (86.0%) were considered appropriate for antiplatelet medication, 32 (7.0%) for anticoagulant medication, and 254 (55.9%) for antihypertensive medication. The rates of nontreatment observed 3 months after the event were 24.4% for antiplatelet, 59.4% for anticoagulant, and 29.5% for antihypertensive medication. Independent risk factors for nontreatment with antithrombotic therapies (antiplatelets and anticoagulants) were the subtype of stroke (nonlacunar infarct: OR=1.60, 95% CI 1.07 to 2.54), stroke severity measured by the Glasgow Coma Scale (GCS) score (GCS &#8804;13: OR 2.08, 95% CI 1.18 to 3.66) and the Barthel Index (BI) score 5 days after the event (BI &#8804;10: OR 1.85, 95% CI 1.17 to 2.93). For antihypertensive therapies the stroke subtype (OR 2.46, 95% CI 1.33 to 4.54), GCS score (OR 2.97, 95% CI 1.35 to 6.53), BI score (OR 2.33, 95% CI 1.27 to 4.29), and ethnicity (Caucasian: OR 2.43, 95% CI 1.15 to 5.14) were independently associated with nontreatment. Cox regression modeling showed no significant association between the treatment status and recurrence-free 3-year survival rates after controlling for severity and subtype of stroke.&lt;/p&gt; &lt;p&gt;Conclusions — Secondary prevention for a common disease such as stroke appears to be inadequate in the study area. Healthcare professionals need to consider antithrombotic and antihypertensive therapies for all stroke patients.&lt;/p&gt

Influence of raised plasma osmolality on clinical outcome after acute stroke

&lt;p&gt;Background and Purpose — Abnormal physiological parameters after acute stroke may induce early neurological deterioration. Studies of the effect of dehydration on stroke outcome are limited. We examined the association of raised plasma osmolality on stroke outcome at 3 months and the change of plasma osmolality with hydration during the first week after stroke.&lt;/p&gt; &lt;p&gt;Methods — Acute stroke patients had their plasma osmolality measured at admission and at days 1, 3, and 7. Maximum plasma osmolality and the area under curve (AUC) were also calculated during the first week. Patients were stratified according to how they were hydrated: orally, intravenously, or both. Outcome included survival at 3 months after stroke. Logistic regression was performed to examine the association between raised plasma osmolality (&#62;296 mOsm/kg) and survival, adjusting for stroke severity. Linear regression was performed to examine the pattern of plasma osmolality across hydration groups.&lt;/p&gt; &lt;p&gt;Results — One hundred sixty-seven patients were included. Mean admission (300 mOsm/kg, SD 11.4), maximum (308.1 mOsm/kg, SD 17.1), and AUC (298.3 mOsm/kg, SD 11.7) plasma osmolality were significantly higher in those who died compared with survivors (293.1 mOsm/kg [SD 8.2], 297.7 mOsm/kg [SD 8.7], and 291.7 mOsm/kg [SD 8.1], respectively; P&#60;0.0001). Admission plasma osmolality &#62;296 mOsm/kg was significantly associated with mortality (OR 2.4, 95% CI 1.0 to 5.9). In patients hydrated intravenously, there was no significant fall in plasma osmolality compared with patients hydrated orally (P=0.68).&lt;/p&gt; &lt;p&gt;Conclusions — Raised plasma osmolality on admission is associated with stroke mortality, after correcting for case mix. Correction of dehydration after stroke requires a more systematic approach. Trials are required to determine whether correcting dehydration after stroke improves outcome.&lt;/p&gt