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- Clarke, R., et al.
(författare)
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Effects of homocysteine lowering with B vitamins on cognitive aging: meta-analysis of 11 trials with cognitive data on 22,000 individuals
- 2014
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Ingår i: American Journal of Clinical Nutrition. - : Elsevier BV. - 0002-9165. ; 100:2, s. 657-666
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Tidskriftsartikel (refereegranskat)abstract
- Background: Elevated plasma homocysteine is a risk factor for Alzheimer disease, but the relevance of homocysteine lowering to slow the rate of cognitive aging is uncertain. Objective: The aim was to assess the effects of treatment with B vitamins compared with placebo, when administered for several years, on composite domains of cognitive function, global cognitive function, and cognitive aging. Design: A meta-analysis was conducted by using data combined from 11 large trials in 22,000 participants. Domain-based z scores (for memory, speed, and executive function and a domain-composite score for global cognitive function) were available before and after treatment (mean duration: 2.3 y) in the 4 cognitive-domain trials (1340 individuals); Mini-Mental State Examination (MMSE) type tests were available at the end of treatment (mean duration: 5 y) in the 7 global cognition trials (20,431 individuals). Results: The domain-composite and MMSE-type global cognitive function z scores both decreased with age (mean SE: 0.054 0.004 and 0.036 0.001/y, respectively). Allocation to B vitamins lowered homocysteine concentrations by 28% in the cognitive-domain trials but had no significant effects on the z score differences from baseline for individual domains or for global cognitive function (z score difference: 0.00; 95% CI: 0.05, 0.06). Likewise, allocation to B vitamins lowered homocysteine by 26% in the global cognition trials but also had no significant effect on end-treatment MMSE-type global cognitive function (z score difference: 0.01; 95% CI: 0.03, 0.02). Overall, the effect of a 25% reduction in homocysteine equated to 0.02 y (95% CI: 0.10, 0.13 y) of cognitive aging per year and excluded reductions of >1 mo per year of treatment. Conclusion: Homocysteine lowering by using B vitamins had no significant effect on individual cognitive domains or global cognitive function or on cognitive aging.
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- Postmus, Iris, et al.
(författare)
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Pharmacogenetic meta-analysis of genome-wide association studies of LDL cholesterol response to statins.
- 2014
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Ingår i: Nature communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 5
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Tidskriftsartikel (refereegranskat)abstract
- Statins effectively lower LDL cholesterol levels in large studies and the observed interindividual response variability may be partially explained by genetic variation. Here we perform a pharmacogenetic meta-analysis of genome-wide association studies (GWAS) in studies addressing the LDL cholesterol response to statins, including up to 18,596 statin-treated subjects. We validate the most promising signals in a further 22,318 statin recipients and identify two loci, SORT1/CELSR2/PSRC1 and SLCO1B1, not previously identified in GWAS. Moreover, we confirm the previously described associations with APOE and LPA. Our findings advance the understanding of the pharmacogenetic architecture of statin response.
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- Perez, A. C., et al.
(författare)
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Thyroid-Stimulating Hormone and Clinical Outcomes: The CORONA Trial (Controlled Rosuvastatin Multinational Study in Heart Failure)
- 2014
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Ingår i: JACC: Heart Failure. - : Elsevier BV. - 2213-1779. ; 2:1, s. 35-40
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Tidskriftsartikel (refereegranskat)abstract
- Objectives: This study sought to examine the association between thyroid status and clinical outcomes in patients in the CORONA (Controlled Rosuvastatin Multinational Trial in Heart Failure) study. Background: Hypo- and hyperthyroidism were associated with worse clinical outcomes in the SCD-HeFT (Sudden Cardiac DeathinHeart Failure Trial). Methods: In CORONA, 4,987 patients underwent baseline thyroid-stimulating hormone (TSH) measurement, 237 of which(4.8%) were receiving thyroid replacement therapy (TRT). Patients were classified as euthyroid (TSH: 0.3 to 5.0μU/ml,and no TRT), hyperthyroid (<0.3 μU/ml and no TRT), or hypothyroid (>5.0 μU/ml and no TRT). The outcome composites of cardiovascular (CV) death or hospitalization for heart failure (HF), the components of this composite, and all-cause death were compared among hyperthyroid, hypothyroid, and euthyroid states, using multivariable models adjusting for previously reported prognostic variables. Results: A total of 91.3% of patients were euthyroid, 5.0% were hypothyroid, and 3.7% were hyperthyroid. Compared with euthyroid patients, hypothyroid patients were more likely to have a history of stroke, had worse renal function andhigher N-terminal pro-B-type natriuretic peptide (NT-proBNP) levels, were more likely to be treated with an antiarrhythmic drug (or have an implantable cardioverter defibrillator), and were less likely to smoke or be treated with a beta-blocker or angiotensin-converting enzyme inhibitor/angiotensin receptor blocker. In univariate analyses, hypothyroidism was associated with an increased risk of the composite outcome of CV death or HF hospitalization (hazard ratio: 1.29; 95% confidence interval: 1.07 to 1.57; p= 0.008), as well as all-cause death (HR: 1.36; 95% confidence interval: 1.03 to 1.76; p= 0.004). However, after adjustment for other known predictors of outcome, the associations were weakened, and when NT-proBNP was added to the models, the association between hypothyroidism and all outcomes was eliminated. Conclusions: Thyroid status is not an independent predictor of outcome in heart failure with reduced ejection fraction. (Controlled Rosuvastatin Multinational Study in Heart Failure [CORONA]; NCT00206310). © 2014 American College of Cardiology Foundation.
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- Harrison, Craig D., et al.
(författare)
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THE XMM CLUSTER SURVEY : THE STELLAR MASS ASSEMBLY OF FOSSIL GALAXIES
- 2012
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Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 752:1, s. 12-
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents both the result of a search for fossil systems (FSs) within the XMM Cluster Survey and the Sloan Digital Sky Survey and the results of a study of the stellar mass assembly and stellar populations of their fossil galaxies. In total, 17 groups and clusters are identified at z < 0.25 with large magnitude gaps between the first and fourth brightest galaxies. All the information necessary to classify these systems as fossils is provided. For both groups and clusters, the total and fractional luminosity of the brightest galaxy is positively correlated with the magnitude gap. The brightest galaxies in FSs (called fossil galaxies) have stellar populations and star formation histories which are similar to normal brightest cluster galaxies (BCGs). However, at fixed group/cluster mass, the stellar masses of the fossil galaxies are larger compared to normal BCGs, a fact that holds true over a wide range of group/cluster masses. Moreover, the fossil galaxies are found to contain a significant fraction of the total optical luminosity of the group/cluster within 0.5 R-200, as much as 85%, compared to the non-fossils, which can have as little as 10%. Our results suggest that FSs formed early and in the highest density regions of the universe and that fossil galaxies represent the end products of galaxy mergers in groups and clusters.
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| 10. |
- Hilton, Matt, et al.
(författare)
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The XMM Cluster Survey : evidence for energy injection at high redshift from evolution of the X-ray luminosity-temperature relation
- 2012
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Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 424:3, s. 2086-2096
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Tidskriftsartikel (refereegranskat)abstract
- We measure the evolution of the X-ray luminositytemperature (LX - T) relation since z similar to 1.5 using a sample of 211 serendipitously detected galaxy clusters with spectroscopic redshifts drawn from the XMM Cluster Survey first data release (XCS-DR1). This is the first study spanning this redshift range using a single, large, homogeneous cluster sample. Using an orthogonal regression technique, we find no evidence for evolution in the slope or intrinsic scatter of the relation since z similar to 1.5, finding both to be consistent with previous measurements at z similar to 0.1. However, the normalization is seen to evolve negatively with respect to the self-similar expectation: we find E-1(z)?LX = 1044.67 +/- 0.09(T/5)3.04 +/- 0.16(1 + z)-1.5 +/- 0.5, which is within 2 sigma of the zero evolution case. We see milder, but still negative, evolution with respect to self-similar when using a bisector regression technique. We compare our results to numerical simulations, where we fit simulated cluster samples using the same methods used on the XCS data. Our data favour models in which the majority of the excess entropy required to explain the slope of the LX - T relation is injected at high redshift. Simulations in which active galactic nucleus feedback is implemented using prescriptions from current semi-analytic galaxy formation models predict the positive evolution of the normalization, and differ from our data at more than 5 sigma. This suggests that more efficient feedback at high redshift may be needed in these models.
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- Lloyd-Davies, E. J., et al.
(författare)
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The XMM Cluster Survey : X-ray analysis methodology
- 2011
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Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 418:1, s. 14-53
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Tidskriftsartikel (refereegranskat)abstract
- The XMM Cluster Survey (XCS) is a serendipitous search for galaxy clusters using all publicly available data in the XMMNewton Science Archive. Its main aims are to measure cosmological parameters and trace the evolution of X-ray scaling relations. In this paper we describe the data processing methodology applied to the 5776 XMM observations used to construct the current XCS source catalogue. A total of 3675 > 4s cluster candidates with > 50 background-subtracted X-ray counts are extracted from a total non-overlapping area suitable for cluster searching of 410 deg2. Of these, 993 candidates are detected with > 300 background-subtracted X-ray photon counts, and we demonstrate that robust temperature measurements can be obtained down to this count limit. We describe in detail the automated pipelines used to perform the spectral and surface brightness fitting for these candidates, as well as to estimate redshifts from the X-ray data alone. A total of 587 (122) X-ray temperatures to a typical accuracy of < 40 (< 10) per cent have been measured to date. We also present the methodology adopted for determining the selection function of the survey, and show that the extended source detection algorithm is robust to a range of cluster morphologies by inserting mock clusters derived from hydrodynamical simulations into real XMMimages. These tests show that the simple isothermal beta-profiles is sufficient to capture the essential details of the cluster population detected in the archival XMM observations. The redshift follow-up of the XCS cluster sample is presented in a companion paper, together with a first data release of 503 optically confirmed clusters.
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| 12. |
- Mehrtens, Nicola, et al.
(författare)
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The XMM Cluster Survey : optical analysis methodology and the first data release
- 2012
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Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 423:2, s. 1024-1052
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Tidskriftsartikel (refereegranskat)abstract
- The XMM Cluster Survey (XCS) is a serendipitous search for galaxy clusters using all publicly available data in the XMMNewton Science Archive. Its main aims are to measure cosmological parameters and trace the evolution of X-ray scaling relations. In this paper we present the first data release from the XMM Cluster Survey (XCS-DR1). This consists of 503 optically confirmed, serendipitously detected, X-ray clusters. Of these clusters, 256 are new to the literature and 357 are new X-ray discoveries. We present 463 clusters with a redshift estimate (0.06 < z < 1.46), including 261 clusters with spectroscopic redshifts. The remainder have photometric redshifts. In addition, we have measured X-ray temperatures (TX) for 401 clusters (0.4 < TX < 14.7 keV). We highlight seven interesting subsamples of XCS-DR1 clusters: (i) 10 clusters at high redshift (z > 1.0, including a new spectroscopically confirmed cluster at z= 1.01); (ii) 66 clusters with high TX (>5 keV); (iii) 130 clusters/groups with low TX (<2 keV); (iv) 27 clusters with measured TX values in the Sloan Digital Sky Survey (SDSS) Stripe 82 co-add region; (v) 77 clusters with measured TX values in the Dark Energy Survey region; (vi) 40 clusters detected with sufficient counts to permit mass measurements (under the assumption of hydrostatic equilibrium); (vii) 104 clusters that can be used for applications such as the derivation of cosmological parameters and the measurement of cluster scaling relations. The X-ray analysis methodology used to construct and analyse the XCS-DR1 cluster sample has been presented in a companion paper, Lloyd-Davies et al.
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| 13. |
- Stott, John P., et al.
(författare)
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The XMM Cluster Survey : the interplay between the brightest cluster galaxy and the intracluster medium via AGN feedback
- 2012
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Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 422:3, s. 2213-2229
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Forskningsöversikt (refereegranskat)abstract
- Using a sample of 123 X-ray clusters and groups drawn from the XMM Cluster Survey first data release, we investigate the interplay between the brightest cluster galaxy (BCG), its black hole and the intracluster/group medium (ICM). It appears that for groups and clusters with a BCG likely to host significant active galactic nuclei (AGN) feedback, gas cooling dominates in those with TX > 2 keV while AGN feedback dominates below. This may be understood through the subunity exponent found in the scaling relation we derive between the BCG mass and cluster mass over the halo mass range 1013 < M500 < 1015 M? and the lack of correlation between radio luminosity and cluster mass, such that BCG AGN in groups can have relatively more energetic influence on the ICM. The LXTX relation for systems with the most massive BCGs, or those with BCGs co-located with the peak of the ICM emission, is steeper than that for those with the least massive and most offset, which instead follows self-similarity. This is evidence that a combination of central gas cooling and powerful, well fuelled AGN causes the departure of the ICM from pure gravitational heating, with the steepened relation crossing self-similarity at TX= 2 keV. Importantly, regardless of their black hole mass, BCGs are more likely to host radio-loud AGN if they are in a massive cluster (TX? 2 keV) and again co-located with an effective fuel supply of dense, cooling gas. This demonstrates that the most massive black holes appear to know more about their host cluster than they do about their host galaxy. The results lead us to propose a physically motivated, empirical definition of cluster and group, delineated at 2 keV.
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| 14. |
- Stott, J. P., et al.
(författare)
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THE XMM CLUSTER SURVEY : THE BUILD-UP OF STELLAR MASS IN BRIGHTEST CLUSTER GALAXIES AT HIGH REDSHIFT
- 2010
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Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 718:1, s. 23-30
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Tidskriftsartikel (refereegranskat)abstract
- We present deep J-and K-s-band photometry of 20 high redshift galaxy clusters between z = 0.8 and 1.5, 19 of which are observed with the MOIRCS instrument on the Subaru telescope. By using near-infrared light as a proxy for stellar mass we find the surprising result that the average stellar mass of Brightest Cluster Galaxies (BCGs) has remained constant at similar to 9 x 10(11) M-circle dot since z similar to 1.5. We investigate the effect on this result of differing star formation histories generated by three well-known and independent stellar population codes and find it to be robust for reasonable, physically motivated choices of age and metallicity. By performing Monte Carlo simulations we find that the result is unaffected by any correlation between BCG mass and cluster mass in either the observed or model clusters. The large stellar masses imply that the assemblage of these galaxies took place at the same time as the initial burst of star formation. This result leads us to conclude that dry merging has had little effect on the average stellar mass of BCGs over the last 9-10 Gyr in stark contrast to the predictions of semi-analytic models, based on the hierarchical merging of dark matter halos, which predict a more protracted mass build-up over a Hubble time. However, we discuss that there is potential for reconciliation between observation and theory if there is a significant growth of material in the intracluster light over the same period.
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| 15. |
- Viana, P. T. P., et al.
(författare)
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The XMM Cluster Survey : Present status and latest results
- 2013
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Ingår i: Astronomical Notes - Astronomische Nachrichten. - : Wiley. - 0004-6337 .- 1521-3994. ; 334:4-5, s. 462-465
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Tidskriftsartikel (refereegranskat)abstract
- The XMM Cluster Survey (XCS) is a serendipitous search for galaxy clusters using all publicly available data in the XMM-Newton Science Archive. Our recent first data release (XCS-DR1) contains 503 optically confirmed groups and clusters, among which 256 new to the literature and 357 whose X-ray emission was detected for the first time. We discuss their properties and provide an update on the work being done. As examples of the applications of XCS-DR1, we mention the 17 fossil groups/clusters identified with the help of the Sloan Digital Sky Survey. Their brightest galaxies have stellar populations and star-formation histories which are similar to normal brightest cluster galaxies, but their stellar masses are significantly larger and correspond to a much bigger fraction of the total group/cluster optical luminosity. We also highlight the 15 clusters expected to be also detected by the Planck satellite, and characterize the expected overlap between the final XCS and Planck cluster catalogues.
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