Kjetil Røysland

• Berg, Erlend; Tegn, Nicolai Kloumann; Abdelnoor, Michael; Røysland, Kjetil; Ryalen, Pål Christie & Aaberge, Lars [Show all 14 contributors for this article] (2023). Long-Term Outcomes of Invasive vs Conservative Strategies for Older Patients With Non–ST-Segment Elevation Acute Coronary Syndromes. Journal of the American College of Cardiology. ISSN 0735-1097. 82(21), p. 2021–2030. doi: 10.1016/j.jacc.2023.09.809. Full text in Research Archive
• Tsarpali, Vasiliki; Midtvedt, Karsten; Lønning, Kjersti; Bernklev, Tomm; Åsberg, Anders & Fawad, Haris [Show all 10 contributors for this article] (2022). A Comorbidity Index and Pretransplant Physical Status Predict Survival in Older Kidney Transplant Recipients: A National Prospective Study. Transplantation direct. ISSN 2373-8731. 8(4). doi: 10.1097/TXD.0000000000001307. Full text in Research Archive Show summary

  Kidney transplantation (KT) is considered the best treatment for end-stage kidney disease (ESKD). In the increasing elderly ESKD population, KT should be reserved for carefully selected candidates who are expected to experience favorable outcomes. We aimed to prospectively evaluate pretransplant recipient factors that may predict patient survival and can eventually guide therapeutic decisions in elderly with ESKD. Methods: Recipient factors were evaluated in KT candidates aged ≥65 y. Comorbidity was assessed at waitlisting according to the Liu comorbidity index (LCI). Health-related quality of life outcomes were measured using the Kidney Disease Quality of Life Short Form, version 1.3. The Cox proportional hazard regression was used to evaluate predictors of patient survival. Results: We included 192 recipients, with a mean age of 72.1 (4.1) y, who were transplanted with kidneys from deceased brain-dead donors. During a median observation period of 4.6 (3.2-6.3) y, 66 recipients died. Elevated LCI consistently predicted poor patient survival. In recipients with LCI ≥4, dialysis >2 y comprised a 2.5-fold increase in mortality risk compared with recipients on dialysis ≤2 y. Self-reported pretransplant physical function was also proven to be a significant positive predictor of survival. Conclusion: The implementation of LCI and a physical function score during the evaluation of older kidney transplant candidates may improve the selection and thereby optimize posttransplant outcomes.

• Ryalen, Pål Christie; Møller, Bjørn; Laache, Christoffer Haug; Stensrud, Mats Julius & Røysland, Kjetil (2021). Prognosis of cancer survivors: estimation based on differential equations. Biostatistics. ISSN 1465-4644. 24(2), p. 345–357. doi: 10.1093/biostatistics/kxab009. Full text in Research Archive
• Andersson, Helene; Jablonski, Greg Eigner; Nordahl, Stein Helge Glad; Nordfalk, Karl; Helseth, Eirik & Martens, Camilla [Show all 8 contributors for this article] (2021). The Risk of Benign Paroxysmal Positional Vertigo After Head Trauma. The Laryngoscope. ISSN 0023-852X. 132(2), p. 443–448. doi: 10.1002/lary.29851. Full text in Research Archive
• Ryalen, Pål Christie; Stensrud, Mats Julius; Fosså, Sophie Dorothea & Røysland, Kjetil (2020). Causal inference in continuous time: an example on prostate cancer therapy. Biostatistics. ISSN 1465-4644. 21(1), p. 172–185. doi: 10.1093/biostatistics/kxy036. Full text in Research Archive
• Stensrud, Mats Julius; Røysland, Kjetil & Ryalen, Pål Christie (2019). On null hypotheses in survival analysis. Biometrics. ISSN 0006-341X. 75(4), p. 1276–1287. doi: 10.1111/biom.13102.
• Hausken, John; Fretland, Åsmund Avdem; Edwin, Bjørn; Andersen, Marit Helen; Dagenborg, Vegar Johansen & Bjørnelv, Gudrun Maria Waaler [Show all 10 contributors for this article] (2019). Intravenous patient-controlled analgesia versus thoracic epidural analgesia after open liver surgery: a prospective, randomized, controlled noninferiority trial. Annals of Surgery. ISSN 0003-4932. 270(2), p. 193–199. doi: 10.1097/SLA.0000000000003209.
• Ryalen, Pål Christie; Stensrud, Mats Julius & Røysland, Kjetil (2019). The additive hazard estimator is consistent for continuous-time marginal structural models. Lifetime Data Analysis. ISSN 1380-7870. 25(4), p. 611–638. doi: 10.1007/s10985-019-09468-y.
• Latysheva, Anna; Emblem, Kyrre Eeg; Brandal, Petter; Vik-Mo, Einar O.; Pahnke, Jens & Røysland, Kjetil [Show all 8 contributors for this article] (2019). Dynamic susceptibility contrast and diffusion MR imaging identify oligodendroglioma as defined by the 2016 WHO classification for brain tumors: histogram analysis approach. Neuroradiology. ISSN 0028-3940. 61(5), p. 545–555. doi: 10.1007/s00234-019-02173-5. Full text in Research Archive Show summary

  Purpose According to the revised World Health Organization (WHO) Classification of Tumors of the Central Nervous System (CNS) of 2016, oligodendrogliomas are now defined primarily by a specific molecular signature (presence of IDH mutation and 1p19q codeletion). The purpose of our study was to assess the value of dynamic susceptibility contrast MR imaging (DSC-MRI) and diffusion-weighted imaging (DWI) to characterize oligodendrogliomas and to distinguish them from astrocytomas. Methods Seventy-one adult patients with untreated WHO grade II and grade III diffuse infiltrating gliomas and known 1p/19q codeletion status were retrospectively identified and analyzed using relative cerebral blood volume (rCBV) and apparent diffusion coefficient (ADC) maps based on whole-tumor volume histograms. The Mann-Whitney U test and logistic regression were used to assess the ability of rCBV and ADC to differentiate between oligodendrogliomas and astrocytomas both independently, but also related to the WHO grade. Prediction performance was evaluated in leave-one-out cross-validation (LOOCV). Results Oligodendrogliomas showed significantly higher microvascularity (higher rCBVMean ≥ 0.80, p = 0.013) and higher vascular heterogeneity (lower rCBVPeak ≤ 0.044, p = 0.015) than astrocytomas. Diffuse gliomas with higher cellular density (lower ADCMean ≤ 1094 × 10−6 mm2/s, p = 0.009) were more likely to be oligodendrogliomas than astrocytomas. Histogram analysis of rCBV and ADC was able to differentiate between diffuse astrocytomas (WHO grade II) and anaplastic astrocytomas (WHO grade III). Conclusion Histogram-derived rCBV and ADC parameter may be used as biomarkers for identification of oligodendrogliomas and may help characterize diffuse gliomas based upon their genetic characteristics. Keywords Diffuse glioma Perfusion MRI Diffusion MRI

• Aalen, Odd O.; Stensrud, Mats Julius; Didelez, Vanessa; Daniel, Rhian; Røysland, Kjetil & Strohmaier, Susanne (2019). Time-dependent mediators in survival analysis: Modeling direct and indirect effects with the additive hazards model. Biometrical Journal. ISSN 0323-3847. p. 1–18. doi: 10.1002/bimj.201800263.
• Stensrud, Mats Julius; Ryalen, Pål Christie & Røysland, Kjetil (2019). Sufficient Cause Interaction for Time-to-event Outcomes. Epidemiology. ISSN 1044-3983. 30(2), p. 189–196. doi: 10.1097/EDE.0000000000000958.
• Ryalen, Pål Christie; Stensrud, Mats Julius & Røysland, Kjetil (2018). Transforming cumulative hazard estimates. Biometrika. ISSN 0006-3444. 105(4), p. 905–916. doi: 10.1093/biomet/asy035. Full text in Research Archive
• Aalen, Odd O.; Gran, Jon Michael; Røysland, Kjetil; Stensrud, Mats Julius & Strohmaier, Susanne (2018). Feedback and Mediation in Causal Inference Illustrated by Stochastic Process Models. Scandinavian Journal of Statistics. ISSN 0303-6898. 45(1), p. 62–86. doi: 10.1111/sjos.12286.
• Gran, Jon Michael; Hoff, Rune; Røysland, Kjetil; Ledergerber, Bruno; Young, James & Aalen, Odd O. (2017). Estimating the treatment effect on the treated under time-dependent confounding in an application to the Swiss HIV Cohort Study. The Journal of the Royal Statistical Society, Series C (Applied Statistics). ISSN 0035-9254. 67(1), p. 103–125. doi: 10.1111/rssc.12221. Full text in Research Archive
• Stensrud, Mats Julius; Aalen, Odd O.; Valberg, Morten & Røysland, Kjetil (2017). Exploring selection bias by causal frailty models: The magnitude matters. Epidemiology. ISSN 1044-3983. 28(3), p. 379–386. doi: 10.1097/EDE.0000000000000621.
• Lund-Johansen, Fridtjof; de la Rosa-Carrillo, Daniel; Mehta, Adi; Sikorski, Krzysztof; Inngjerdingen, Marit & Kalina, Tomáš [Show all 11 contributors for this article] (2016). MetaMass, a tool for meta-analysis of subcellular proteomics data. Nature Methods. ISSN 1548-7091. 13(10), p. 837–840. doi: 10.1038/nmeth.3967.
• Hovdenes, Jan; Røysland, Kjetil; Nielsen, Niklas; Kjærgaard, Jesper; Wanscher, Michael & Hassager, Christian [Show all 18 contributors for this article] (2016). A low body temperature on arrival at hospital following out-of-hospital-cardiac-arrest is associated with increased mortality in the TTM-study. Resuscitation. ISSN 0300-9572. 107, p. 102–106. doi: 10.1016/j.resuscitation.2016.08.011.
• Aalen, Odd O.; Røysland, Kjetil; Gran, Jon Michael; Kouyos, Roger & Lange, Theis (2016). Can we believe the DAGs? A comment on the relationship between causal DAGs and mechanisms. Statistical Methods in Medical Research. ISSN 0962-2802. 25(5), p. 2294–2314. doi: 10.1177/0962280213520436.
• Strohmaier, Susanne; Røysland, Kjetil; Hoff, Rune; Borgan, Ørnulf; Pedersen, Terje Rolf & Aalen, Odd O. (2015). Dynamic path analysis - a useful tool to investigate mediation processes in clinical survival trials. Statistics in Medicine. ISSN 0277-6715. 34(29), p. 3866–3887. doi: 10.1002/sim.6598.
• Aalen, Odd O.; Cook, Richard J. & Røysland, Kjetil (2015). Does Cox analysis of a randomized survival study yield a causal treatment effect? Lifetime Data Analysis. ISSN 1380-7870. 21(4), p. 579–593. doi: 10.1007/s10985-015-9335-y.
• Nygård, Mari; Røysland, Kjetil; Campbell, Suzanne & Dillner, Joakim (2014). Comparative effectiveness study on human papillomavirus detection methods used in the cervical cancer screening programme. BMJ Open. ISSN 2044-6055. doi: 10.1136/bmjopen-2013-003460.
• Sanchez-Niubo, Albert; Aalen, Odd O.; Domingo-Salvany, Antonia; Amundsen, Ellen Johanna; Fortiana, Josep & Røysland, Kjetil (2013). A multi-state model to estimate incidence of heroin use. BMC Medical Research Methodology. ISSN 1471-2288. 13. doi: 10.1186/1471-2288-13-4. Show summary

  Existing incidence estimates of heroin use are usually based on one information source. This study aims to incorporate more sources to estimate heroin use incidence trends in Spain between 1971 and 2005. A multi-state model was constructed, whereby the initial state “heroin consumer” is followed by transition to either “admitted to first treatment” or to “left heroin use” (i.e. permanent cessation or death). Heroin use incidence and probabilities of entering first treatment ever were estimated following a back-calculation approach. The highest heroin use incidence rates in Spain, around 1.5 per 1,000 inhabitants aged 10–44, occurred between 1985 and 1990; subdividing by route of administration reveals higher incidences of injection between 1980 and 1985 (a mean of 0.62 per 1.000) and a peak for non-injectors in 1990 (0.867 per 1,000). A simple conceptual model for heroin users’ trajectories related to treatment admission, provided a broader view of the historical trend of heroin use incidence in Spain.

• Aalen, Odd O.; Røysland, Kjetil; Gran, Jon Michael & Ledergerber, Bruno (2012). Causality, mediation and time: a dynamic viewpoint. Journal of the Royal Statistical Society: Series A (Statistics in Society). ISSN 0964-1998. 175(4), p. 831–861. doi: 10.1111/j.1467-985X.2011.01030.x.
• Tropé, Ameli Ellen Claesdotter; Sjøborg, Katrine Dønvold; Nygård, Mari; Røysland, Kjetil; Campbell, Suzanne & Alfsen, Glenny Cecilie [Show all 7 contributors for this article] (2012). Cytology and Human Papillomavirus Testing 6 to 12 Months after ASCUS or LSIL Cytology in Organized Screening To Predict High-Grade Cervical Neoplasia between Screening Rounds. Journal of Clinical Microbiology. ISSN 0095-1137. 50(6), p. 1927–1935. doi: 10.1128/JCM.00265-12.
• Røysland, Kjetil (2012). COUNTERFACTUAL ANALYSES WITH GRAPHICAL MODELS BASED ON LOCAL INDEPENDENCE. Annals of Statistics. ISSN 0090-5364. 40(4), p. 2162–2194. doi: 10.1214/12-AOS1031.
• Røysland, Kjetil; Gran, Jon Michael; Ledergerber, Bruno; von Wyl, Viktor; Young, James A. & Aalen, Odd O. (2011). Analyzing direct and indirect effects of treatment using dynamic path analysis applied to data from the Swiss HIV Cohort Study. Statistics in Medicine. ISSN 0277-6715. 30(24), p. 2947–2958. doi: 10.1002/sim.4324.
• Røysland, Kjetil (2011). A martingale approach to continuous time marginal structural models. Bernoulli. ISSN 1350-7265. 17(3), p. 895–915. doi: 10.3150/10-BEJ303.
• Røysland, Kjetil (2011). Frames generated by actions of countable discrete groups. Transactions of the American Mathematical Society. ISSN 0002-9947. 363(1), p. 95–108. doi: 10.1090/s0002-9947-2010-05260-2.
• Gran, Jon Michael; Røysland, Kjetil; Wolbers, Marcel; Didelez, Vanessa; Sterne, Jonathan AC & Ledergerber, Bruno [Show all 9 contributors for this article] (2010). A sequential Cox approach for estimating the causal effect of treatment in the presence of time-dependent confounding applied to data from the Swiss HIV Cohort Study. Statistics in Medicine. ISSN 0277-6715. 29(26), p. 2757–2768. doi: 10.1002/sim.4048.
• Gjessing, Håkon K.; Røysland, Kjetil; Aalen, Odd O. & Pena, Edsel A (2010). Recurrent events and the exploding Cox model. Lifetime Data Analysis. ISSN 1380-7870. 16(4), p. 525–546. doi: 10.1007/s10985-010-9180-y.
• Røysland, Kjetil (2008). Symmetries in projective multiresolution analyses. Journal of Fourier Analysis and Applications. ISSN 1069-5869. 14(2), p. 267–285.
• Røysland, Kjetil & Dutkay, Dorin (2008). Covariant Representations for Matrix-valued Transfer Operators. Integral equations and operator theory. ISSN 0378-620X. 62(3), p. 383–410. doi: 10.1007/s00020-008-1623-4.
• Dutkay, Dorin & Røysland, Kjetil (2007). The algebra of harmonic functions for a matrix-valued transfer operator. Journal of Functional Analysis. ISSN 0022-1236. 252(2), p. 734–762. doi: 10.1016/j.jfa.2007.04.014.

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• Fretland, Åsmund Avdem; Hausken, Jon; Edwin, B; Andersen, Marit Helen; Dagenborg, Vegar Johansen & Kristiansen, Ronny [Show all 9 contributors for this article] (2018). Does ketorolac have an opioid sparing effect after open liver resection? Data from the Oslo-COMET trial.
• Frank, Anna-Simone Josefine; Lupattelli, Angela; Røysland, Kjetil & Nordeng, Hedvig Marie Egeland (2017). Patterns and Predictors of Hypothyroid Medication Use in Relation to Pregnancy: A Drug Utilization Study.
• Frank, Anna-Simone Josefine; Lupattelli, Angela; Røysland, Kjetil & Nordeng, Hedvig Marie Egeland (2017). Risk factors for discontinuation of hypothyroid medication in early pregnancy -- a study from the Norwegian Mother and Child Cohort Study and the Medical Birth Registry of Norway.
• Frank, Anna-Simone Josefine; Lupattelli, Angela; Røysland, Kjetil & Nordeng, Hedvig Marie Egeland (2017). PATTERNS AND PREDICTORS OF HYPOTHYROID MEDICATION USE IN RELATION TO PREGNANCY: A DRUG UTILIZATION STUDY.
• Røysland, Kjetil (2010). Interventions with identifiable consequences.
• Røysland, Kjetil (2010). A Marginal Structural Model in Continuous Time.
• Røysland, Kjetil (2010). A marginal structural model in continuous time.
• Røysland, Kjetil (2010). A marginal structural model in continuous time.
• Røysland, Kjetil (2009). Transfer operators and harmonic bundle maps.
• Røysland, Kjetil (2009). A marginal structural model in continuous time.
• Røysland, Kjetil (2006). Transfer operators on bundle maps.

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