Prof. dr O.M. Dekkers (Olaf)

Internist and clinical epidemiologist


Olaf Dekkers is professor of research methodology at the departments of Clinical Epidemiology and Endocrinology. He is adjunct professor at the department of Clinical Epidemiology at Aarhus University (Denmark). He studied medicine philosophy and graduated (MA) on the ‘truth definition according to Frege’. He was trained in epidemiology (MSc) at the London Scholl of Hygiene and Tropical Medicine.

Research topics are epidemiology of endocrine diseases, meta-analysis and methodology of research. He works in close collaboration with the Institute of Social and Preventive Medicine in Bern (Switzerland) on and with the department of Clinical Epidemiology in Aarhus (Denmark).  He is methodological chair of the guideline committee of the European Society of Endocrinology.    

Main Research Themes

1.            Epidemiology of endocrine diseases.

Epidemiology of endocrine diseases, mainly diabetes mellitus and thyroid disease. Member of the steering committee of the NEO study. From the start involved in the TRUST study, an FP-7 granted RCT on the effect of levothyroxine treatment in subclinical hypothyroidism. Collaboration with the Department of Clinical Epidemiology of Aarhus University (Denmark) since 2011, to use nationwide covering databases for the study of endocrine diseases.

2.            Guideline development for European Society of Endocrinology

Methodological chair of the Guideline Committee of the European Society of Endocrinology. Guidelines published on Hypoparathyroidism (2015), Adrenal Incidentaloma (2016), Pheochromocytomas (2016), Turner Syndrome (2017), Aggressive Pituitary Tumors and Adrenal Carcinoma (2018).

3.            Meta-analysis

Initiator and consultant for several meta-analytic projects, with a focus on meta-analysis of observational studies. Actual membership of the COSMOS consortium (with Prof. Douglas Altman, Prof. Matthias Egger and Prof. Jan Vandenbroucke) aiming to produce a guidance paper on how to perform meta-analyses of observational studies.

4.            Methodology

Study of the methodology of research. ZonMW granted project on instrumental variable analysis, with focus on the physician’s preference as instrumental variable. Instrumental variable analysis is a promising method to circumvent confounding by indication in observational studies. Publication on the distinction between case series and cohort studies in the Annals of Internal Medicine. In close collaboration with Prof Matthias Egger (Bern, Switzerland) several papers where published on use and misuse of noninferiority trials. Current PhD projects on measurement error and network meta-analysis. Recent contribution to a Routledge Companion book Philosophy in Medicine, chapter on Observational studies.



Key publicaties:

  • Feller M, Snel M, Mooijaart S, Quinn T, Stott D, Westendorp R, Rodondi N, Dekkers OM. Association of Thyroid Hormone Therapy With Quality of Life and Thyroid-Related Symptoms in Patients With Subclinical Hypothyroidism: A Systematic Review and Meta-analysis. JAMA. 2018 Oct 2;320(13):1349-1359. doi: 10.1001/jama.2018.13770.JAMA. 2018.PMID: 30285179

  • Fassnacht M , Arlt W, Bancos I, Dralle H, Newell-Price J, Sahdev A, Tabarin A, Terzolo M, Tsagarakis S, and Dekkers OM. Management of adrenal incidentalomas: European Society of Endocrinology Clinical Practice Guideline in collaboration with the European Network for the Study of Adrenal Tumors. Eur J Endocrinol. 2016 Aug;175(2):G1-G34.
  • COSMOS-E: Guidance on conducting systematic reviews and meta-analyses of observational studies of etiology. PLoS Med. 2019 Feb 21;16(2). Dekkers OM, Vandenbroucke JP, Cevallos M, Renehan AG, Altman DG, Egger M.
  • Stegeman BH, de Bastos M, Rosendaal FR, van Hylckama Vlieg A, Helmerhorst FM, Stijnen T, Dekkers OM. Network meta-analysis of different combined oral contraceptives and the risk of venous thrombosis. BMJ 2013, Sep 12;347.
  • Dekkers OM, Horváth-Puhó E, Jørgensen JO, Cannegieter SC, Ehrenstein V, Vandenbroucke JP, Pereira AM, Sørensen HT. Multisystem morbidity and mortality in Cushing's syndrome: a cohort study. J Clin Endocrinol Metab. 2013 Jun;98(6):2277-84.
  • von Bartheld MB, Dekkers OM, Szlubowski A, Eberhardt R, Herth FJ, in 't Veen JC, de Jong YP, van der Heijden EH, Tournoy KG, Claussen M, van den Blink B, Shah PL, Zoumot Z, Clementsen P, Porsbjerg C, Mauad T, Bernardi FD, van Zwet EW, Rabe  KF, Annema JT. Endosonography vs conventional bronchoscopy for the diagnosis of sarcoidosis: the GRANULOMA randomized clinical trial. JAMA. 2013 Jun 19;309(23):2457-64.
  • Johannesdottir SA, Horváth-Puhó E, Dekkers OM, Cannegieter SC, Jørgensen JO, Ehrenstein V, Vandenbroucke JP, Pedersen L, Sørensen HT. Use of glucocorticoids and risk of venous thromboembolism: a nationwide population-based case-control study. JAMA Intern Med. 2013 May 13;173(9):743-52.
  • Dekkers OM, Egger M, Altman DG, Vandenbroucke JP. Distinguishing case series from cohort studies. Ann Intern Med. 2012 Jan 3;156:37-40.
  • Gast KB, Tjeerdema N, StijnenT, SmitJWA, Dekkers OM, Insulin resistance and risk of incident cardiovascular events in non-diabetic adults: meta-analysis, Plos One 2012;7(12):e52036.
  • Burgers AM, Biermasz NR, Schoones JW, Pereira AM, Renehan AG, Zwahlen M, Egger M, Dekkers OM. Meta-analysis and dose-response metaregression: circulating insulin-like growth factor I (igf-I) and mortality. J Clin Endocrinol Metab. 2011 Sep;96(9):2912-20.
  • Soonawala D, Middelburg RA, Egger M, Vandenbroucke JP and Dekkers OM. Efficacy of experimental treatments compared with standard treatments in non-inferiority trials: A meta-analysis of randomized controlled trials. Int J Epidemiol. 2010 Dec;39(6):1567-81.
  • Dekkers OM, Biermasz NR, Pereira AM, Roelfsema F, van Aken MO, Voormolen JH and Romijn JA. Mortality in patients treated for Cushing's disease is increased, compared with patients treated for nonfunctioning pituitary macroadenoma. J Clin Endocrinol Metab. 2007 Mar;92(3):976-81.


Publicaties op PubMed van O.M. Dekkers


Leids Universitair Medisch Centrum
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