| 51. |
- Sundström, Johan, Professor, 1971-, et al.
(författare)
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Rationale for a Swedish cohort consortium
- 2019
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Ingår i: Upsala Journal of Medical Sciences. - : Taylor & Francis Group. - 0300-9734 .- 2000-1967. ; 124:1, s. 21-28
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Tidskriftsartikel (refereegranskat)abstract
- We herein outline the rationale for a Swedish cohort consortium, aiming to facilitate greater use of Swedish cohorts for world-class research. Coordination of all Swedish prospective population-based cohorts in a common infrastructure would enable more precise research findings and facilitate research on rare exposures and outcomes, leading to better utilization of study participants' data, better return of funders' investments, and higher benefit to patients and populations. We motivate the proposed infrastructure partly by lessons learned from a pilot study encompassing data from 21 cohorts. We envisage a standing Swedish cohort consortium that would drive development of epidemiological research methods and strengthen the Swedish as well as international epidemiological competence, community, and competitiveness.
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| 52. |
- Sundström, Johan, Professor, 1971-, et al.
(författare)
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Risk factors for subarachnoid haemorrhage : a nationwide cohort of 950 000 adults
- 2019
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Ingår i: International Journal of Epidemiology. - : Oxford University Press. - 0300-5771 .- 1464-3685. ; 48:6, s. 2018-2025
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Subarachnoid haemorrhage (SAH) is a devastating disease, with high mortality rate and substantial disability among survivors. Its causes are poorly understood. We aimed to investigate risk factors for SAH using a novel nationwide cohort consortium.METHODS: We obtained individual participant data of 949 683 persons (330 334 women) between 25 and 90 years old, with no history of SAH at baseline, from 21 population-based cohorts. Outcomes were obtained from the Swedish Patient and Causes of Death Registries.RESULTS: During 13 704 959 person-years of follow-up, 2659 cases of first-ever fatal or non-fatal SAH occurred, with an age-standardized incidence rate of 9.0 [95% confidence interval (CI) (7.4-10.6)/100 000 person-years] in men and 13.8 [(11.4-16.2)/100 000 person-years] in women. The incidence rate increased exponentially with higher age. In multivariable-adjusted Poisson models, marked sex interactions for current smoking and body mass index (BMI) were observed. Current smoking conferred a rate ratio (RR) of 2.24 (95% CI 1.95-2.57) in women and 1.62 (1.47-1.79) in men. One standard deviation higher BMI was associated with an RR of 0.86 (0.81-0.92) in women and 1.02 (0.96-1.08) in men. Higher blood pressure and lower education level were also associated with higher risk of SAH.CONCLUSIONS: The risk of SAH is 45% higher in women than in men, with substantial sex differences in risk factor strengths. In particular, a markedly stronger adverse effect of smoking in women may motivate targeted public health initiatives.
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| 53. |
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| 54. |
- Svennblad, Bodil, et al.
(författare)
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Fundamental differences between the Methods of Maximum Likelihood and Maximum Posterior Probabilities in Phylogenetics
- 2006
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Ingår i: Systematic Biology. - : Oxford University Press (OUP). - 1063-5157 .- 1076-836X. ; 55:1, s. 116-121
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Tidskriftsartikel (refereegranskat)abstract
- Using a four-taxon example under a simple model of evolution, we show that the methods of maximum likelihood and maximum posterior probability (which is a Bayesian method of inference) may not arrive at the same optimal tree topology. Some patterns that are separately uninformative under the maximum likelihood method are separately informative under the Bayesian method. We also show that this difference has impact on the bootstrap frequencies and the posterior probabilities of topologies, which therefore are not necessarily approximately equal. Efron et al. (Proc. Natl. Acad. Sci. USA 93:13429-13434, 1996) stated that bootstrap frequencies can, under certain circumstances, be interpreted as posterior probabilities. This is true only if one includes a noninformative prior distribution of the possible data patterns, and most often the prior distributions are instead specified in terms of topology and branch lengths.
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| 55. |
- Svennblad, Bodil, et al.
(författare)
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Improving divergence time estimation in phylogenetics : More taxa vs. longer sequences
- 2007
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Ingår i: Statistical Applications in Genetics and Molecular Biology. - : Walter de Gruyter GmbH. - 1544-6115 .- 1544-6115 .- 2194-6302. ; 6, s. 35-
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Tidskriftsartikel (refereegranskat)abstract
- Maximum Likelihood (ML) is used as a standard method for estimating divergence times in phylogenetic trees. The method is consistent and hence the precision can be improved by analyzing longer sequences. In this paper we show that the precision can be improved also by including more taxa to the existing tree. It is a theoretical study, complemented with simulations, showing that the gain in precision is faster with increasing sequence length than with increasing number of taxa. We further compare the results of estimating divergence times using Maximum Likelihood with the much faster and less complex estimation method of Mean Path Length (MPL), which works with the evolution model of Jukes-Cantor (1969). It is shown that MPL is as good as ML in estimating divergence times of nodes that are located near the root in the tree, but ML is better in estimating the divergence times of nodes lower down.
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| 56. |
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| 57. |
- Svennblad, Bodil, 1966-
(författare)
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On Estimating Topology and Divergence Times in Phylogenetics
- 2008
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This PhD thesis consists of an introduction and five papers, dealing with statistical methods in phylogenetics.A phylogenetic tree describes the evolutionary relationships among species assuming that they share a common ancestor and that evolution takes place in a tree like manner. Our aim is to reconstruct the evolutionary relationships from aligned DNA sequences.In the first two papers we investigate two measures of confidence for likelihood based methods, bootstrap frequencies with Maximum Likelihood (ML) and Bayesian posterior probabilities. We show that an earlier claimed approximate equivalence between them holds under certain conditions, but not in the current implementations of the two methods.In the following two papers the divergence times of the internal nodes are considered. The ML estimate of the divergence time of the root is improved if longer sequences are analyzed or if more taxa are added. We show that the gain in precision is faster with longer sequences than with more taxa. We also show that the algorithm of the software package PATHd8 may give biased estimates if the global molecular clock is violated. A change of the algorithm to obtain unbiased estimates is therefore suggested.The last paper deals with non-informative priors when using the Bayesian approach in phylogenetics. The term is not uniquely defined in the literature. We adopt the idea of data translated likelihoods and derive the so called Jeffreys' prior for branch lengths using Jukes Cantor model of evolution.
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| 58. |
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| 59. |
- Tängdén, Thomas, et al.
(författare)
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Radical reduction of cephalosporin use at a tertiary hospital after educational antibiotic intervention during an outbreak of extended-spectrum beta-lactamase-producing Klebsiella pneumoniae
- 2011
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Ingår i: Journal of Antimicrobial Chemotherapy. - : Oxford University Press (OUP). - 0305-7453 .- 1460-2091. ; 66:5, s. 1161-1167
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Tidskriftsartikel (refereegranskat)abstract
- Objectives: During an outbreak of extended-spectrum beta-lactamase (ESBL)-producing Klebsiella pneumoniae at our hospital, we performed an educational antibiotic intervention aimed at reducing prescriptions of second- and third-generation cephalosporins and preventing increased use of fluoroquinolones and carbapenems. In this report, we describe the implementation strategy used and evaluate the intervention effect according to Cochrane recommendations. Methods: New recommendations for empirical intravenous antibiotic treatment were communicated to prescribers throughout the hospital by infectious diseases physicians working with Strama (the Swedish strategic programme against antibiotic resistance). No restrictive measures were used. The intervention effect was analysed with interrupted time series (ITS) regression analysis of local and national monthly antibiotic sales data. Results: A radical immediate and sustained reduction was demonstrated for the cephalosporins targeted in the intervention, whereas consumption of piperacillin/tazobactam and penicillin G increased substantially. Fluoroquinolone and carbapenem use was essentially unchanged. The ESBL outbreak subsided and no increased resistance to piperacillin/tazobactam was detected in K. pneumoniae, Escherichia coli or Pseudomonas aeruginosa blood isolates during the 2.5 year follow-up. Conclusions: Our study clearly demonstrates that an educational intervention can have an immediate and profound effect on antibiotic prescription patterns at a large tertiary hospital. ITS regression analysis of local and national antibiotic sales data was valuable to readily assess the immediate and sustained effects of the intervention.
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| 60. |
- Ueda, Peter, et al.
(författare)
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External Validation of the DAPT Score in a Nationwide Population
- 2018
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Ingår i: Journal of the American College of Cardiology. - : ELSEVIER SCIENCE INC. - 0735-1097 .- 1558-3597. ; 72:10, s. 1069-1078
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND The dual antiplatelet therapy (DAPT) score guides decisions on DAPT duration after coronary stenting by simultaneously predicting ischemic and bleeding risk. OBJECTIVES This study sought to assess the performance of the DAPT score in a nationwide real-world population. METHODS The study used register data in Sweden (2006 to 2014) and followed 41,101 patients who had undergone 12 months of event-free DAPT, from months 12 to 30 after stenting. Risk of myocardial infarction (MI) or stent thrombosis, major adverse cardiovascular and cerebrovascular events (MACCE) (MI, stroke, and all-cause death), and fatal or major bleeding were compared according to DAPT score. RESULTS The score had a discrimination of 0.58 (95% confidence interval [CI]: 0.56 to 0.60) for MI or stent thrombosis, 0.54 (95% CI: 0.53 to 0.55) for MACCE, and 0.49 (95% CI: 0.45 to 0.53) for fatal or major bleeding. Risk of MI or stent thrombosis was significantly increased at scores of >= 3 while MACCE risk followed a J-shaped pattern and increased at scores of >= 4. Absolute differences in fatal or major bleeding risk were small between scores. Event rates of ischemic and bleeding outcomes in patients with high (>= 2) and low (< 2) scores differed compared to the DAPT Study from which the score was derived; fatal or major bleeding rates were approximately one-half of those in the placebo arm of the DAPT Study. CONCLUSIONS In a nationwide population, the DAPT score did not adequately discriminate ischemic and bleeding risk, the relationship between score and ischemic risk did not correspond to the suggested decision rule for extended DAPT, and risk of bleeding was lower compared with the DAPT Study. The score and its decision rule may not be generalizable to real-world populations.
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