Per Henrik Zahl

Responsibilities

Medical Biostatistics, Screening, RCT, QALY analyses;

Projects and publications

Per Henrik Zahl, Karsten Juhl Jørgensen, (2022). Estimation of Breast Cancer Overdiagnosis in a U.S. Breast Screening Cohort. Annals of Internal Medicine s. W114-W115. doi: 10.7326/L22-0275
Per Henrik Zahl, Mette Kalager, Pål Suhrke, Erik Nord, (2019). Quality-of-life effects of screening mammography in Norway. International Journal of Cancer doi: 10.1002/ijc.32539
Truls Erik Bjerklund Johansen, Per Henrik Zahl, Eduard Baco, Riccardo Bartoletti, Gernot Bonkat, Franck Bruyere, Tommaso Cai, Mete Cek, Ekaterina Kulchavenya, Béla Köves, Vladimir Mouraviev, Adrian Pilatz, Zafer Tandogdu, Peter Tenke, Florian M.E. Wagenlehner, (2019). Antibiotic resistance, hospitalizations, and mortality related to prostate biopsy: first report from the Norwegian Patient Registry. World Journal of Urology s. 1-10. doi: 10.1007/s00345-019-02837-0
Wenche Ryberg, Per Henrik Zahl, Lien My Diep, Nils Inge Landrø, Roar Fosse, (2019). Managing suicidality within specialized care: A randomized controlled trial. Journal of Affective Disorders s. 112-120. doi: 10.1016/j.jad.2019.02.022
Per Henrik Zahl, Anne Reneflot, (2018). Selvmord og selvmordsforsøk i Norge.
Minna Johansson, Per Henrik Zahl, Volkert Siersma, Karsten Juhl Jørgensen, Bertil Marklund, John Brodersen, (2018). Benefits and harms of screening men for abdominal aortic aneurysm in Sweden: a registry-based cohort study. The Lancet s. 2441-2447. doi: 10.1016/S0140-6736(18)31031-6
Ingvild Maria Tøllefsen, Erlend Hem, Øivind Ekeberg, Per Henrik Zahl, Karin Helweg-Larsen, (2017). Differing Procedures for Recording Mortality Statistics in Scandinavia. Crisis s. 123-130. doi: 10.1027/0227-5910/a000425
Karsten Juhl Jørgensen, Peter C Gøtzsche, Mette Kalager, Per Henrik Zahl, (2017). Breast cancer screening in Denmark: A cohort study of tumor size and overdiagnosis. Annals of Internal Medicine s. 313-323. doi: 10.7326/M16-0270
Karsten Juhl Jørgensen, Mette Kalager, Alexandra Barratt, Cornelia Baines, Per Henrik Zahl, John Brodersen, Russell P Harris, (2017). Overview of guidelines on breast screening: Why recommendations differ and what to do about it. Breast s. 261-269. doi: 10.1016/j.breast.2016.08.002
Christian Haga, Mimi Stokke Opdal, Silja Skogstad Tuv, Per Henrik Zahl, Hanne Stenberg-Nilsen, (2016). Legemiddelsikkerhet ved bytte av digitalispreparat i Norge. Tidsskrift for Den norske legeforening s. 1714-1718. doi: 10.4045/tidsskr.15.0161
Wenche Ryberg, Roar Fosse, Per Henrik Zahl, Inge Brorson, Paul Møller, Nils Inge Landrø, David Jobes, (2016). Collaborative Assessment and Management of Suicidality (CAMS) compared to treatment as usual (TAU) for suicidal patients: Study protocol for a randomized controlled trial. Trials doi: 10.1186/s13063-016-1602-z
Ingvild Maria Tøllefsen, Ingemar Thiblin, Karin Helweg-Larsen, Erlend Hem, Marianne Kastrup, Ullakarin Nyberg, Sidsel Rogde, Per Henrik Zahl, Gunvor Furu Østevold, Øivind Ekeberg, (2016). Accidents and undetermined deaths: Re-evaluation of nationwide samples from the Scandinavian countries. BMC Public Health doi: 10.1186/s12889-016-3135-5
Ingvild Maria Tøllefsen, Karin Helweg-Larsen, Ingemar Thiblin, Erlend Hem, Marianne Kastrup, Ullakarin Nyberg, Sidsel Rogde, Per Henrik Zahl, Gunvor Furu Østevold, Øivind Ekeberg, (2015). Are suicide deaths under-reported? Nationwide re-evaluations of 1800 deaths in Scandinavia. BMJ Open doi: 10.1136/bmjopen-2015-009120
Pål Suhrke, Per Henrik Zahl, (2015). Breast cancer incidence and menopausal hormone therapy in Norway from 2004 to 2009: a register-based cohort study. Cancer Medicine s. 1303-1308. doi: 10.1002/cam4.474
Per Henrik Zahl, Jan Mæhlen, (2015). Bias in observational studies of the association between menopausal hormone therapy and breast cancer. PLOS ONE doi: 10.1371/journal.pone.0124076
Per Henrik Zahl, Karsten Juhl Jørgensen, Peter C Gøtzsche, (2014). Lead-time models should not be used to estimate overdiagnosis in cancer screening. Journal of General Internal Medicine (JGIM) s. 1283-1286. doi: 10.1007/s11606-014-2812-2
Per Henrik Zahl, Karsten Juhl Jørgensen, Peter C Gøtzsche, (2013). Overestimated lead times in cancer screening has led to substantial underestimation of overdiagnosis. British Journal of Cancer s. 2014-2019. doi: 10.1038/bjc.2013.427
Pål Suhrke, Jan Mæhlen, Per Henrik Zahl, (2012). Hormone Therapy Use and Breast Cancer Incidence by Histological Subtypes in Sweden and Norway. The Breast Journal s. 549-556. doi: 10.1111/tbj.12001
Peter C Gøtzsche, Karsten Juhl Jørgensen, Per Henrik Zahl, Jan Mæhlen, (2012). Why mammography screening has not lived up to expectations from the randomised trials. Cancer Causes and Control s. 15-21. doi: 10.1007/s10552-011-9867-8
Per Henrik Zahl, Jan Mæhlen, (2012). Overdiagnostikk av brystkreft etter 14 år med mammografiscreening. Tidsskrift for Den norske legeforening s. 414-417. doi: 10.4045/tidsskr.11.0195
Per Henrik Zahl, (2012). Voldsomme dødsfall. s. 55-56.
Per Henrik Zahl, Peter C Gøtzsche, Jan Mæhlen, (2011). Natural history of breast cancers detected in the Swedish mammography screening programme: a cohort study. The Lancet Oncology s. 1118-1124. doi: 10.1016/S1470-2045(11)70250-9
Pål Suhrke, Jan Mæhlen, Ellen Schlichting, Karsten Juhl Jørgensen, Peter C Gøtzsche, Per Henrik Zahl, (2011). Effect of mammography screening on surgical treatment for breast cancer in Norway: comparative analysis of cancer registry data. BMJ. British Medical Journal doi: 10.1136/bmj.d4692
Bernard Junod, Per Henrik Zahl, Robert M Kaplan, Jørn Olsen, Sander Greenland, (2011). An investigation of the apparent breast cancer epidemic in France: screening and incidence trends in birth cohorts. BMC Cancer doi: 10.1186/1471-2407-11-401
Håkon Andre Johannessen, Gudrun Klemetsdal Dieserud, Bjørgulf Claussen, Per Henrik Zahl, (2011). Changes in mental health services and suicide mortality in Norway: an ecological study. BMC Health Services Research doi: 10.1186/1472-6963-11-68
Håkon Andre Johannessen, Gudrun Klemetsdal Dieserud, Diego De Leo, Bjørgulf Claussen, Per Henrik Zahl, (2011). Chain of care for patients who have attempted suicide: a follow-up study from Bærum, Norway. BMC Public Health doi: 10.1186/1471-2458-11-81
Karsten Juhl Jørgensen, Per Henrik Zahl, Peter C Gøtzsche, (2010). Breast cancer mortality in organised mammography screening in Denmark : comparative study. BMJ. British Medical Journal doi: 10.1136/bmj.c1241
Per Henrik Zahl, Diego De Leo, Øivind Ekeberg, Heidi Marie Hjelmeland, Gudrun Klemetsdal Dieserud, (2010). The relationship between sales of SSRI, TCA and suicide rates in the Nordic countries. BMC Psychiatry doi: 10.1186/1471-244X-10-62
Håkon André Johannessen, Gudrun Klemetsdal Dieserud, Fredrik Jakhelln, Per Henrik Zahl, Diego De Leo, (2009). Changes in institutional psychiatric care and suicidal behaviour: a follow-up study of inpatient suicide attempters in Bærum, Norway. Social Psychiatry and Psychiatric Epidemiology s. 845-851. doi: 10.1007/s00127-009-0006-8
Karsten J Jørgensen, Per Henrik Zahl, Peter Gøtzsche, (2009). Overdiagnosis in organised mammography screening in Denmark. A comparative study. BMC Women's Health doi: 10.1186/1472-6874-9-36
Per Henrik Zahl, Jan Mæhlen, Gilbert Welch, (2008). The natural history of invasive breast cancers detected by screening mammography. Archives of Internal Medicine s. 2311-2316.
Odd Steffen Dalgard, Arnstein Mykletun, Marit Aase Rognerud, Rune Johansen, Per Henrik Zahl, (2007). Education, sense of mastery and mental health: results from a nation wide health monitoring study in Norway. BMC Psychiatry doi: 10.1186/1471-244X-7-20
Per Henrik Zahl, (2007). Mammografiscreening - mest til skade?. Samfunnsspeilet : Tidsskrift om levekår og livsstil
Per Henrik Zahl, Peter C Gøtzsche, Jannike Mørch Andersen, Jan Mæhlen, (2006). Results of the Two-County trial of mammography screening are not compatible with contemporaneous official Swedish breast cancer statistics. Danish Medical Bulletin s. 438-440.
Marit Aase Rognerud, Per Henrik Zahl, (2006). Social inequalities in mortality: changes in the relative importance of income, education and household size over a 27-year period. European Journal of Public Health s. 62-68. doi: 10.1093/eurpub/cki070
Bjørn Heine Strand, Aage Tverdal, Bjørgulf Claussen, Per-Henrik Zahl, (2005). Is birth history the key to highly educated women's higher breast cancer mortality? A follow-up study of 500,000 women aged 35-54. International Journal of Cancer s. 1002-1006.
Per Henrik Zahl, (2003). Vitenskapelige kriterier for innføring og evaluering av screening. Tidsskrift for Den norske legeforening s. 333-336.
Per Henrik Zahl, Marit Aase Rognerud, Bjørn Heine Strand, (2003). Sosial ulikhet og utvikling i dødelighet hos enslige i Norge. Tidsskrift for Den norske legeforening s. 1822-1825.
Per Henrik Zahl, (2003). Regression analysis with multiplicative and time-varying additive regression coefficients with examples from breast and colon cancer. Statistics in Medicine s. 1113-1127. doi: 10.1002/sim.971
Per-Henrik Zahl, Branko Kopjar, Jan Mæhlen, (2001). Norske tall for brystkreftdødlighet og validitet i svenske mammografistudier. Tidsskrift for Den norske legeforening s. 1928-1931.

Per Henrik Zahl, (2014). Folkehelserapporten 2014: Helsetilstanden i Norge(Befolkning i Norge side 38-31 og Selvmord og selvmordsforsøk s 180-4)
Øyvind Erik Næss, Marit Aase Rognerud, Bjørn Heine Strand, Else-Karin Grøholt, Sidsel Graff-Iversen, Anett Arntzen, Odd Steffen Dalgard, Malin M C Eberhard-Gran, Merete Åse Eggesbø, Rune Johansen, Petter Kristensen, Eiliv Lund, Marit Låg, Kristin Schjelderup Mathiesen, Marita Melhus, Haakon E Meyer, Per Nafstad, Kari Slinning, Anne-Johanne Søgaard, Leila Torgersen, Margarete E. Vollrath, Per Henrik Zahl, (2007). Sosial ulikhet i helse : en faktarapport
Per Henrik Zahl, (2003). Bedre helse - større forskjeller. En analyse av hvordan inntekt, utdanning og husholdningsstørrelse har påvirket dødeligheten i befolkningen i periodene 1970-77, 1980-87 og 1990-97

Truls E. Bjerklund Johansen, Tommaso Cai, Kurt Naber, Lindsay E. Nicolle, Zafer Tandogdu, Tone Tonjum, Florian Wagenlehner, Per Henrik Zahl, Béla Köves, (2021). Gravide bør screenes for asymptomatisk bakteriuri. Tidsskrift for Den norske legeforening s. 1-5. doi: 10.4045/tidsskr.21.0379
Vinod Sharma, Philippe Autier, Paula B. Gordon, H. Gilbert Welch, Per Henrik Zahl, Marije F. Bakker, Stéphanie V. De Lange, Carla H. Van Gils, (2020). MRI Screening in Women with Dense Breasts. New England Journal of Medicine s. 1283-1284. doi: 10.1056/NEJMc1917231
Per Henrik Zahl, Mette Kalager, (2020). Reply to: Loss of QALY in mammography screening reported by Zahl et al.. International Journal of Cancer doi: 10.1002/ijc.32755
Per Henrik Zahl, Ivar Sønbø Kristiansen, (2020). Re: Stage-specific survival has improved for young breast cancer patients since 2000: but not equally?. Breast Cancer Research and Treatment s. 527-528. doi: 10.1007/s10549-020-05941-7
Per Henrik Zahl, (2020). RE: Breast Cancer Mortality After Implementation of Organized Population-Based Screening in Norway. Journal of the National Cancer Institute doi: 10.1093/jnci/djaa129
Minna Johansson, Per Henrik Zahl, Volkert Dirk Siersma, Karsten Juhl Jørgensen, Bertil Marklund, John Brodersen, (2019). Screening for abdominal aortic aneurysm – Authors' reply. The Lancet s. 28-28. doi: 10.1016/S0140-6736(18)32742-9
Per Henrik Zahl, (2018). Hva lærte politikere av innføringen av mammografiscreening?. Tidsskrift for Den norske legeforening s. 1105-1105. doi: 10.4045/tidsskr.18.0550
Per Henrik Zahl, (2018). Dags för oberoende granskning av det svenska screeningprogrammet. Läkartidningen
Per Henrik Zahl, (2018). Screening kan orsaka mer skada än nytta..
Per Henrik Zahl, (2018). En varslet katastrofe i norsk helsevesen. .
Per Henrik Zahl, (2018). Letter comments on EJC published paper: 'No overdiagnosis in the Norwegian Breast Cancer Screening Program estimated by combining record linkage and questionnaire information in the Norwegian Women and Cancer study'. European Journal of Cancer s. 49-50. doi: 10.1016/j.ejca.2018.03.025
Karsten Juhl Jørgensen, Peter C. Gøtzsche, Mette Kalager, Per Henrik Zahl, (2017). In response. Annals of Internal Medicine s. 524-524. doi: 10.7326/L17-0270
Per Henrik Zahl, (2016). Re: Norsk mammografiscreening – mange selvmotsigelser i evalueringen. Tidsskrift for Den norske legeforening s. 1875-1875. doi: 10.4045/tidsskr.16.0971
Per Henrik Zahl, (2015). Overdiagnostikk gjør oss sykere..
Per Henrik Zahl, (2015). Re: Forekomsten av føflekkreft øker igjen. Tidsskrift for Den norske legeforening doi: 10.4045/tidsskr.15.0384
Karsten Juhl Jørgensen, Per Henrik Zahl, Peter C. Gøtzsche, (2015). Influence of mammography screening on use of mastectomies in Denmark. Acta Oncologica s. 133-134. doi: 10.3109/0284186X.2014.920958
Peter C. Gøtzsche, Karsten Juhl Jørgensen, Per Henrik Zahl, (2014). Lead-time models produce far too low estimates of overdiagnosis with mammographic screening. Journal of the American College of Radiology doi: 10.1016/j.jacr.2014.08.008
Per Henrik Zahl, (2014). Re: Mammografiscreening bør avvikles. Tidsskrift for Den norske legeforening s. 1546-1547. doi: 10.4045/tidsskr.14.0981
Per Henrik Zahl, (2014). Re: Hvorfor er resultater fra organisert mamografiscreening så vanskelig å tolke?. Tidsskrift for Den norske legeforening s. 1544-1545. doi: 10.4045/tidsskr.14.0916
Per Henrik Zahl, (2014). Adjusting the incidence increase when screening for statistical lead time will always give estimates of overdiagnosis close to zero. Breast Cancer Research doi: 10.1186/bcr3671
Per Henrik Zahl, (2013). Informasjon om mammografiscreening er ikke nøytral. Tidsskrift for Den norske legeforening s. 1557-1558.
Per Henrik Zahl, Pål Suhrke, Karsten Juhl Jørgensen, (2013). Overdiagnosis of breast cancer in Norway: What have the authors adjusted for?. International Journal of Cancer s. 2754-2755. doi: 10.1002/ijc.28248
Per Henrik Zahl, (2013). The benefits and harms of breast cancer screening. The Lancet s. 801-802. doi: 10.1016/S0140-6736(13)60623-6
Per Henrik Zahl, (2012). Overdiagnosis of Invasive Breast Cancer due to Mammography Screening. Annals of Internal Medicine s. 220-221.
K Jørgensen, Mette Kalager, Per Henrik Zahl, Vinjar Fønnebø, (2012). Comparing attendees with non-attendees in breast screening does not provide useful information about an effect on prognostic features or mortality. Breast Cancer Research and Treatment s. 617-618. doi: 10.1007/s10549-012-2250-y
Karsten Juhl Jørgensen, John D. Keen, Per Henrik Zahl, Peter C. Gøtzsche, (2012). The two-county breast screening trial cannot provide a reliable estimate of the effect of breast cancer screening. Radiology s. 729-730. doi: 10.1148/radiol.11111756
Per Henrik Zahl, Gudrun Klemetsdal Dieserud, Øivind Ekeberg, Heidi Marie Hjelmeland, Diego De Leo, (2011). The relationship between sales of SSRI, TCA and suicide rates in the Nordic countries.
Karsten Jørgensen, Per Henrik Zahl, Peter Gøtzsche, (2011). More on Screening Mammography. New England Journal of Medicine s. 284-284.
Peter C Gøtzsche, Karsten Jørgensen, Per Henrik Zahl, (2010). Breast screening: why estimates differ by a factor of 20-25. Journal of Medical Screening s. 158-159. doi: 10.1258/jms.2010.010066
Per Henrik Zahl, (2010). Breast Cancer Awareness Month. Still Awaiting Screening Facts. The BMJ
PC Gøtzsche, KJ Jørgensen, Jan Mæhlen, Per Henrik Zahl, (2009). Estimation of lead time and overdiagnosis in breast cancer screening. British Journal of Cancer s. 219-219. doi: 10.1038/sj.bjc.6604762
P Suhrke, Per Henrik Zahl, Jan Mæhlen, (2009). Declining breast cancer incidence and decreased HRT use. The Lancet s. 460-461.
Donald A Berry, Cornelia J Baines, Michael Baum, Kay Dickersin, Suzanne W Fletcher, Peter C Gøtzsche, Karsten Juhl Jørgensen, Bernard Junod, Jan Mæhlen, Lisa M Schwartz, H Gilbert Welch, Steven Woloshin, Hazel Thornton, Per Henrik Zahl, (2009). Flawed inferences about screening mammography's benefit based on observational data. Journal of Clinical Oncology s. 639-640. doi: 10.1200/JCO.2008.17.9341
Per Henrik Zahl, Jan Mæhlen, HG Welch, (2009). Breast cancer overdiagnosis with screening mammography. Archives of Internal Medicine s. 1000-1001.
Per Henrik Zahl, (2008). Ingen effekt av organisert screening for livmorhalskreft. Tidsskrift for Den norske legeforening
Per Henrik Zahl, Karsten Juhl Jørgensen, Jan Mæhlen, Peter C Gøtzsche, (2008). Biases in estimates of overdetection due to mammography screening. The Lancet Oncology s. 199-201. doi: 10.1016/S1470-2045(08)70049-4
Per Henrik Zahl, Jan Mæhlen, (2007). Constant relative survival rates in Sweden and Norway when adjusting for screening-related overdiagnosis. International Journal of Cancer s. 2279-2279. doi: 10.1002/ijc.22497
Per Henrik Zahl, (2007). Bias when calculating breast cancer mortality after screening mammography in British Columbia. International Journal of Cancer doi: 10.1002/ijc.22623
Peter C Gøtzsche, Jan Mæhlen, Per Henrik Zahl, (2007). Undeclared motives in withdrawing a publication. The Lancet
Per Henrik Zahl, Jan Mæhlen, (2007). A decline in breast-cancer incidence. New England Journal of Medicine s. 509-511.
Per Henrik Zahl, Jan Mæhlen, (2007). Reply to Tabar's critique.
Per Henrik Zahl, Jan Mæhlen, (2006). Ramifications of screening for breast cancer - Definition of overdiagnosis is confusing in follow-up of Malmo trial. BMJ. British Medical Journal
Peter C Gøtzsche, Jan Mæhlen, Per Henrik Zahl, (2006). What is publication?. The Lancet s. 1854-1856.
Per Henrik Zahl, Jan Mæhlen, (2006). Do model results suggest spontaneous regression of breast cancer?. International Journal of Cancer s. 2647-2647. doi: 10.1002/ijc.21634
Per Henrik Zahl, Jan Mæhlen, HG Welch, (2005). On the fate of DCIS in the absence of mammography screening. Cancer Epidemiology, Biomarkers and Prevention
Per Henrik Zahl, Jan Mæhlen, (2005). Model of outcomes of screening mammography – spontaneous regression of breast cancer may not be uncommon. BMJ. British Medical Journal doi: 10.1136/bmj.331.7512.350-a
Per Henrik Zahl, (2005). An inverse association between tumour size and overdiagnosis may explain the results by Bucchi et al. British Journal of Cancer doi: 10.1038/sj.bjc.6602581
Per Henrik Zahl, Jan Mæhlen, (2005). Reduction in mortality from breast cancer: decrease with screening was marked in younger age group. BMJ. British Medical Journal doi: 10.1136/bmj.330.7498.1024
Per-Henrik Zahl, Jan Mæhlen, (2004). Overdiagnostikk og mammografiscreening. Tidsskrift for Den norske legeforening
Per-Henrik Zahl, Jan Mæhlen, (2004). P.-H. Zahl & J. Mæhlen svarer. Tidsskrift for Den norske legeforening s. 2800-2801.
Per-Henrik Zahl, Jan Mæhlen, (2004). Svar til Kjersti Bakken. Har østrogenbehandling betydning for insidens av brystkreft?. Tidsskrift for Den norske legeforening s. 2801-2801.
Jan Mæhlen, Per-Henrik Zahl, (2004). Unjustified conclusion on overdiagnosis. BMJ. British Medical Journal
Per-Henrik Zahl, Jan Mæhlen, (2004). Overdiagnosis in mammography screening. Journal of the American Medical Association (JAMA) s. 1064-1073.
Per-Henrik Zahl, Bjørn Heine Strand, Jan Mæhlen, (2004). Incidence of breast cancer in Norway and Sweden during introduction of nationwide screening:prospective cohort study. BMJ. British Medical Journal
Jan Mæhlen, Per-Henrik Zahl, (2004). Evidence for Spontaneous Regression of Sub-Clinical Invasive Breast Cancers.
Per-Henrik Zahl, Jan Mæhlen, (2004). Overdiagnosis of Breast Cancer in the Norwegian Mammography Screening Program.
Per Henrik Zahl, (2004). Overdiagnosis of breast cancer in Denmark. British Journal of Cancer doi: 10.1038/sj.bjc.6601738

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Mobile: +47 975 48 451

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Myrens verksted 2, 0473 Oslo

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Per Henrik Zahl

Senior Scentist

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Projects and publications

Projects

Scientific articles and book chapters

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