Kjetil Røysland

• Berg, Erlend; Tegn, Nicolai Kloumann; Abdelnoor, Michael; Røysland, Kjetil; Ryalen, Pål Christie & Aaberge, Lars [Vis alle 14 forfattere av denne artikkelen] (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), s. 2021–2030. doi: 10.1016/j.jacc.2023.09.809. Fulltekst i vitenarkiv
• Tsarpali, Vasiliki; Midtvedt, Karsten; Lønning, Kjersti; Bernklev, Tomm; Åsberg, Anders & Fawad, Haris [Vis alle 10 forfattere av denne artikkelen] (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. Fulltekst i vitenarkiv Vis sammendrag

  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), s. 345–357. doi: 10.1093/biostatistics/kxab009. Fulltekst i vitenarkiv
• Andersson, Helene; Jablonski, Greg Eigner; Nordahl, Stein Helge Glad; Nordfalk, Karl; Helseth, Eirik & Martens, Camilla [Vis alle 8 forfattere av denne artikkelen] (2021). The Risk of Benign Paroxysmal Positional Vertigo After Head Trauma. The Laryngoscope. ISSN 0023-852X. 132(2), s. 443–448. doi: 10.1002/lary.29851. Fulltekst i vitenarkiv
• 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), s. 172–185. doi: 10.1093/biostatistics/kxy036. Fulltekst i vitenarkiv
• Stensrud, Mats Julius; Røysland, Kjetil & Ryalen, Pål Christie (2019). On null hypotheses in survival analysis. Biometrics. ISSN 0006-341X. 75(4), s. 1276–1287. doi: 10.1111/biom.13102.
• Hausken, John; Fretland, Åsmund Avdem; Edwin, Bjørn; Andersen, Marit Helen; Dagenborg, Vegar Johansen & Bjørnelv, Gudrun Maria Waaler [Vis alle 10 forfattere av denne artikkelen] (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), s. 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), s. 611–638. doi: 10.1007/s10985-019-09468-y.
• Latysheva, Anna; Emblem, Kyrre Eeg; Brandal, Petter; Vik-Mo, Einar O.; Pahnke, Jens & Røysland, Kjetil [Vis alle 8 forfattere av denne artikkelen] (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), s. 545–555. doi: 10.1007/s00234-019-02173-5. Fulltekst i vitenarkiv Vis sammendrag

  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. s. 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), s. 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), s. 905–916. doi: 10.1093/biomet/asy035. Fulltekst i vitenarkiv
• 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), s. 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), s. 103–125. doi: 10.1111/rssc.12221. Fulltekst i vitenarkiv
• 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), s. 379–386. doi: 10.1097/EDE.0000000000000621.
• Lund-Johansen, Fridtjof; de la Rosa-Carrillo, Daniel; Mehta, Adi; Sikorski, Krzysztof; Inngjerdingen, Marit & Kalina, Tomáš [Vis alle 11 forfattere av denne artikkelen] (2016). MetaMass, a tool for meta-analysis of subcellular proteomics data. Nature Methods. ISSN 1548-7091. 13(10), s. 837–840. doi: 10.1038/nmeth.3967.
• Hovdenes, Jan; Røysland, Kjetil; Nielsen, Niklas; Kjærgaard, Jesper; Wanscher, Michael & Hassager, Christian [Vis alle 18 forfattere av denne artikkelen] (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, s. 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), s. 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), s. 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), s. 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. Vis sammendrag

  Overgang fra injisering til sniffing/røyking av heroin Røyking og sniffing av heroin er en mye mindre skadelig inntaksmåte enn injisering. Norge ligger dessverre på toppen i Europa i antall narkotikadødsfall per innbygger. Dette er knyttet til stort omfang av heroinbruk blant brukere av tunge illegale narkotiske stoffer og at heroinet inntas med sprøyte. For å redusere narkotikadødsfall og overdoser må det arbeides for at injisering av heroinbruk reduseres, både ved å redusere rekruttering til heroinbruk, hjelpe eksisterende brukere til å slutte helt eller gå over til substitusjonsbehandling og å arbeide for at røyking og sniffing blir mer populært i brukergruppa. I Spania, nærmere bestemt i Madrid og Barcelona, har en forskergruppe beregnet at rekrutteringen til heroinbruk steg jevnt fra 1970 til ca. 1990, for deretter å falle drastisk fram mot 2006. Et annet funn var at blant de som ble rekruttert til heroinbruk var det fra midten av 80-tallet mer vanlig å røyke stoffet (chase the dragon) enn å injisere det (Sânchez-Niubò et al 2013). Annen litteratur om bruk av heroin i Spania påpeker at det ikke har vært tiltak fra myndighetenes side som har bidratt til redusert rekruttering til heroinbruk og røyking av det istedenfor injisering. Hovedforklaringene knyttes til ulike subkulturer og heroinmarkeder i spanske regioner. I regioner hvor det hvite heroinet dominerte, ble stoffet injisert, mens i regioner hvor det brune heroinet dominerte ble det røykt i mye større grad. Når det hvite heroinet forsvant fra markedet, økte omfanget av røyking. Spania har hatt en stor HIV epidemi blant sprøytebrukere, men risikoen for å bli HIV smittet ser ikke ut til å ha påvirket overgangen til sniffing (de la Fuente et al. 1996, 1997a og 1997b). Det er altså ikke så mye lærdom om virksomme tiltak å hente fra Spania til Norge. Men er det mulig å påvirke markedet og injeksjonskulturen ved å se til teori og empiri om endring av risikoatferd??

• 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), s. 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 [Vis alle 7 forfattere av denne artikkelen] (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), s. 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), s. 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), s. 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), s. 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), s. 95–108. doi: 10.1090/s0002-9947-2010-05260-2.
• Gran, Jon Michael; Røysland, Kjetil; Wolbers, Marcel; Didelez, Vanessa; Sterne, Jonathan AC & Ledergerber, Bruno [Vis alle 9 forfattere av denne artikkelen] (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), s. 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), s. 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), s. 267–285.
• Røysland, Kjetil & Dutkay, Dorin (2008). Covariant Representations for Matrix-valued Transfer Operators. Integral equations and operator theory. ISSN 0378-620X. 62(3), s. 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), s. 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 [Vis alle 9 forfattere av denne artikkelen] (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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