Sven Ove Samuelsen

• Babigumira, Ronnie; Veierød, Marit Bragelien; Hosgood, H. Dean; Samuelsen, Sven Ove; Bråtveit, Magne & Kirkeleit, Jorunn [Show all 13 contributors for this article] (2023). Benzene exposure and risk of lung cancer in the Norwegian Offshore Petroleum Worker cohort: a prospective case-cohort study. Occupational and Environmental Medicine. ISSN 1351-0711. 81(1). doi: 10.1136/oemed-2023-109139. Full text in Research Archive Show summary

  Objective The objective of our study was to examine whether occupational exposure to benzene is associated with lung cancer among males in the Norwegian Offshore Petroleum Workers cohort. Methods Among 25 347 male offshore workers employed during 1965–1998, we conducted a case-cohort study with 399 lung cancer cases diagnosed between 1999 and 2021, and 2035 non-cases sampled randomly by 5-year birth cohorts. Individual work histories were coupled to study-specific job-exposure matrices for benzene and other known lung carcinogens. Weighted Cox regression was used to estimate HRs and 95% CIs for the associations between benzene exposure and lung cancer, by major histological subtypes, adjusted for age, smoking and occupational exposure to welding fumes, asbestos and crystalline silica. Missing data were imputed. Results For lung cancer (all subtypes combined), HRs (95% CIs) for the highest quartiles of benzene exposure versus unexposed were 1.15 (0.61 to 2.35) for cumulative exposure, 1.43 (0.76 to 2.69) for duration, and 1.22 (0.68 to 2.18) for average intensity (0.280≤P-trend≤0.741). For 152 adenocarcinoma cases, a positive trend was observed for exposure duration (P-trend=0.044). Conclusions In this cohort of offshore petroleum workers generally exposed to low average levels of benzene, we did not find an overall clear support for an association with lung cancer (all subtypes combined), although an association was suggested for duration of benzene exposure and adenocarcinoma. The limited evidence might be due to restricted statistical power.

• Shala, Nita Kaupang; Stenehjem, Jo; Babigumira, Ronnie; Liu, Fei-Chih; Berge, Leon Alexander Mclaren & Silverman, Debra T. [Show all 16 contributors for this article] (2023). Exposure to benzene and other hydrocarbons and risk of bladder cancer among male offshore petroleum workers. British Journal of Cancer. ISSN 0007-0920. 129(5), p. 838–851. doi: 10.1038/s41416-023-02357-0. Full text in Research Archive Show summary

  Background Occupational exposures constitute the second leading cause of urinary bladder cancer after tobacco smoking. Increased risks have been found in the petroleum industry, but high-quality exposure data are needed to explain these observations. Methods Using a prospective case-cohort design, we analysed 189 bladder cancer cases (1999–2017) and 2065 randomly drawn non-cases from the Norwegian Offshore Petroleum Workers cohort. Cases were identified in the Cancer Registry of Norway, while work histories (1965–1998) and lifestyle factors were recorded by questionnaire at baseline (1998). Occupational petroleum-related hydrocarbon exposures were assessed by expert-developed job-exposure matrices. Hazard ratios were estimated by weighted Cox-regressions, adjusted for age, tobacco smoking, education, and year of first employment, and with lagged exposures. Results Increased risks were found in benzene-exposed workers, either long-term exposure (≥18.8 years, HR = 1.89, 95% CI: 1.14–3.13; p-trend = 0.044) or high-level cumulative benzene exposure (HR = 1.60, 95% CI: 0.97–2.63; p-trend = 0.065), compared with the unexposed. Associations persisted with 20-year exposure lag. No associations were found with skin or inhalation exposure to crude oil, mineral oil (lubrication, hydraulics, turbines, drilling), or diesel exhaust. Conclusions The results suggest that exposures in the benzene fraction of the petroleum stream may be associated with increased bladder cancer risk.

• Berge, Leon Alexander Mclaren; Liu, Fei-Chih; Grimsrud, Tom Kristian; Babigumira, Ronnie; Støer, Nathalie Charlotte & Kjærheim, Kristina [Show all 15 contributors for this article] (2022). Night shift work and risk of aggressive prostate cancer in the Norwegian Offshore Petroleum Workers (NOPW) cohort. International Journal of Epidemiology. ISSN 0300-5771. 52(4), p. 1003–1014. doi: 10.1093/ije/dyac235. Full text in Research Archive Show summary

  Background: Night shift work may acutely disrupt the circadian rhythm, with possible carcinogenic effects. Prostate cancer has few established risk factors though night shift work, a probable human carcinogen, may increase the risk. We aimed to study the association between night shift work and chlorinated degreasing agents (CDAs) as possible endocrine disrupters in relation to aggressive prostate cancer as verified malignancies. Methods: We conducted a case-cohort study on 299 aggressive prostate cancer cases and 2056 randomly drawn non-cases in the Norwegian Offshore Petroleum Workers cohort (1965-98) with linkage to the Cancer Registry of Norway (1953-2019). Work history was recorded as years with day, night, and rollover (rotating) shift work, and CDA exposure was assessed with expert-made job-exposure matrices. Weighted Cox regression was used to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) for aggressive prostate cancer, adjusted for education and year of first employment, stratified by 10-year birth cohorts, and with 10, 15, and 20 years of exposure lag periods. Results: Compared with day work only, an increased hazard of aggressive prostate cancer (HR = 1.86, 95% CI 1.18-2.91; P-trend = 0.046) was found in workers exposed to ≥19.5 years of rollover shift work. This persisted with longer lag periods (HR = 1.90, 95% CI 0.92-3.95; P-trend = 0.007). The exposure-hazard curve for a non-linear model increased linearly (HRs ≥1.00) for 18-26 years of rollover shift work. No association was found with CDA exposure. Conclusions: Long-term exposure to rollover shift work may increase the hazard of aggressive prostate cancer in offshore petroleum workers.

• Samuelsen, Sven Ove (2022). Cox regression can be collapsible and Aalen regression can be non-collapsible. Lifetime Data Analysis. ISSN 1380-7870. doi: 10.1007/s10985-022-09578-0. Full text in Research Archive
• Fischer, Nantje; Træen, Bente & Samuelsen, Sven Ove (2022). Sexual Debut Ages in Heterosexual Norwegians Across Six Birth Cohorts. Sexuality & Culture. ISSN 1095-5143. doi: 10.1007/s12119-022-10045-z. Full text in Research Archive
• Bekkhus, Mona; Lee, Yunsung; Samuelsen, Sven Ove; Tsotsi, Stella & Magnus, Per Minor (2022). Maternal and paternal anxiety during pregnancy: Comparing the effects on behavioral problems in offspring. PLOS ONE. ISSN 1932-6203. 17(10). doi: 10.1371/journal.pone.0275085. Full text in Research Archive
• Lawrence, Graeme; Midtervoll, Ingvild K.; Samuelsen, Sven Ove; Kristoffersen, Anne Karin; Enersen, Morten & Lund Håheim, Lise (2022). The blood microbiome and its association to cardiovascular disease mortality: case-cohort study. BMC Cardiovascular Disorders. ISSN 1471-2261. 22(1). doi: 10.1186/s12872-022-02791-7. Full text in Research Archive
• Liu, Fei-Chih; Veierød, Marit Bragelien; Kjærheim, Kristina; Robsahm, Trude Eid; Ghiasvand, Reza & Hosgood, H Dean [Show all 17 contributors for this article] (2022). Night shift work, chemical coexposures and risk of female breast cancer in the Norwegian Offshore Petroleum Workers (NOPW) cohort: A prospectively recruited case-cohort study. BMJ Open. ISSN 2044-6055. 12(1). doi: 10.1136/bmjopen-2021-056396. Full text in Research Archive Show summary

  Objectives This study examined the association between night shift work and risk of breast cancer, overall and by hormone receptor subtype, among females in the Norwegian Offshore Petroleum Workers (NOPW) cohort. We also examined the association of coexposure (chlorinated degreasers and benzene) and breast cancer risk, and possible interaction with work schedule. Design Prospectively recruited case- cohort study within the NOPW cohort. Setting Female offshore petroleum workers active on the Norwegian continental shelf. Participants 600 female workers (86 cases and 514 non- cases) were included in the study. We excluded workers that died or emigrated before start of follow-up, had missing work history, were diagnosed with breast cancer or other prior malignancy (except non-melanoma skin cancer) before start of follow-up. Results No overall association was found between breast cancer risk and work schedule (HR 0.87, 95% CI 0.52 to 1.46 for work schedule involving night shift vs day shift only). There was no significant association between work schedule and risk of any breast cancer subtype. No significant interactions were found between work schedule and chemical coexposures (breast cancer overall Pinteraction chlorinated degreasers =0.725 and Pinteraction benzene =0.175). Conclusions Our results did not provide supporting evidence that work schedule involving night shift affects breast cancer risk in female offshore petroleum workers, but should be considered cautiously due to few cases. Further studies with larger sample sizes are warranted

• Bekkhus, Mona; Lee, Yunsung; Brandlistuen, Ragnhild Eek; Samuelsen, Sven Ove & Magnus, Per Minor (2021). Maternal Anxiety and Infants Birthweight and Length of Gestation. A sibling design. BMC Psychiatry. ISSN 1471-244X. 21. doi: 10.1186/s12888-021-03620-5. Full text in Research Archive
• Rossow, Ingeborg Margrete; Amundsen, Ellen Johanna & Samuelsen, Sven Ove (2020). Socio‐economic differences in all‐cause mortality in people with alcohol use disorder: a prospective cohort study. Addiction. ISSN 0965-2140. 116(1), p. 53–59. doi: 10.1111/add.15070. Full text in Research Archive
• Stenehjem, Jo S.; Babigumira, Ronnie; Dean Hosgood, H; Veierød, Marit Bragelien; Samuelsen, Sven Ove & Bråtveit, Magne [Show all 18 contributors for this article] (2020). Cohort Profile: The Norwegian Offshore Petroleum Workers (NOPW) Cohort. International Journal of Epidemiology. ISSN 0300-5771. doi: 10.1093/ije/dyaa107. Full text in Research Archive
• Stoltenberg, Emil Aas; Nordeng, Hedvig Marie Egeland; Ystrøm, Eivind & Samuelsen, Sven Ove (2020). The cure model in perinatal epidemiology. Statistical Methods in Medical Research. ISSN 0962-2802. 29(10), p. 2783–2794. doi: 10.1177/0962280220904092. Full text in Research Archive
• Gunnes, Nina; Gjessing, Håkon K.; Bakken, Inger Johanne Landsjøåsen; Ghaderi, Sara; Gran, Jon Michael & Hungnes, Olav [Show all 13 contributors for this article] (2020). Seasonal and pandemic influenza during pregnancy and risk of fetal death: A Norwegian registry‑based cohort study. European Journal of Epidemiology (EJE). ISSN 0393-2990. 35, p. 371–379. doi: 10.1007/s10654-020-00600-z. Full text in Research Archive
• Hjellvik, Vidar; de Bruin, Marie L.; Samuelsen, Sven Ove; Karlstad, Øystein; Andersen, Morten & Haukka, Jari [Show all 9 contributors for this article] (2019). Adjusting for unmeasured confounding using validation data: Simplified two-stage calibration for survival and dichotomous outcomes. Statistics in Medicine. ISSN 0277-6715. doi: 10.1002/sim.8131. Full text in Research Archive
• Samuelsen, Sven Ove & Støer, Nathalie Charlotte (2018). Inverse Probability Weighting in Nested Case-Control Studies. In Borgan, Ørnulf; Breslow, Norman E.; Chatterjee, Nilanjan; Gail, Mitchell H.; Scott, Alastair & Wild, Christopher J. (Ed.), Handbook of Statistical Methods for Case-Control Studies. CRC Press. ISSN 978-1-4987-6858-0. p. 351–371. doi: 10.1002/sim.6019.
• Borgan, Ørnulf & Samuelsen, Sven Ove (2018). Cohort Sampling for Time-to-Event Data: An Overview. In Borgan, Ørnulf; Breslow, Norman E.; Chatterjee, Nilanjan; Gail, Mitchell H.; Scott, Alastair & Wild, Christopher J. (Ed.), Handbook of Statistical Methods for Case-Control Studies. CRC Press. ISSN 978-1-4987-6858-0. p. 285–301.
• Bekkhus, Mona; Lee, Yunsung; Nordhagen, Rannveig; Magnus, Per; Samuelsen, Sven Ove & Borge, Anne Inger Helmen (2018). Re-examining the link between prenatal maternal anxiety and child emotional difficulties, using a sibling design. International Journal of Epidemiology. ISSN 0300-5771. 47(1), p. 156–165. doi: 10.1093/ije/dyx186. Full text in Research Archive
• Stenehjem, Jo Steinson; Robsahm, Trude Eid; Bråtveit, Magne; Samuelsen, Sven Ove; Kirkeleit, Jorunn & Grimsrud, Tom Kristian (2017). Ultraviolet radiation and skin cancer risk in offshore workers. Occupational Medicine. ISSN 0962-7480. 67(7), p. 569–573. doi: 10.1093/occmed/kqx110. Full text in Research Archive
• Stenehjem, Jo Steinson; Robsahm, Trude Eid; Bråtveit, Magne; Samuelsen, Sven Ove; Kirkeleit, Jorunn & Grimsrud, Tom Kristian (2017). Aromatic hydrocarbons and risk of skin cancer by anatomical site in 25 000 male offshore petroleum workers. American Journal of Industrial Medicine. ISSN 0271-3586. 60(8), p. 679–688. doi: 10.1002/ajim.22741. Full text in Research Archive
• Støer, Nathalie & Samuelsen, Sven Ove (2016). MultipleNCC: Inverse probability weighting of nested case-control data. The R Journal. ISSN 2073-4859. 8(2), p. 5–18. doi: 10.32614/rj-2016-030.
• Meyer, Haakon E; Støer, Nathalie; Samuelsen, Sven Ove; Blomhoff, Rune; Robsahm, Trude Eid & Brustad, Magritt [Show all 8 contributors for this article] (2016). Long Term Association between Serum 25-Hydroxyvitamin D and Mortality in a Cohort of 4379 Men. PLOS ONE. ISSN 1932-6203. 11(3). doi: 10.1371/journal.pone.0151441. Full text in Research Archive
• Træen, Bente; Samuelsen, Sven Ove & Roen, Katrina (2016). Sexual Debut Ages in Heterosexual, Lesbian, Gay, and Bisexual Young Adults in Norway. Sexuality & Culture. ISSN 1095-5143. p. 1–18. doi: 10.1007/s12119-016-9353-2. Show summary

  This study estimates sexual debut ages in young heterosexual, lesbian, gay, and bisexual men and women in Norway. A questionnaire survey was completed online by 27.2 % of a representative national web sample of 2,090 persons aged 18–29 years. Three self-selected samples of 924 respondents completed an extended version of the survey online. Lesbian and bisexual women reported earlier experience of orgasm through masturbation than heterosexual women (median 13.1 versus 15.2 years), and heterosexual men (median 13.5) reported earlier debut than heterosexual women. There was a statistically significant difference between heterosexual and lesbian and bisexual women’s age at the first experience of receptive vaginal sex (median 16.8 versus 15.4 years). As regards experience of insertive vaginal sex, a significantly higher percentage of heterosexual men than women, and of heterosexual and lesbian and bisexual women, reported experience. It was more common among lesbian and bisexual women than heterosexual women to have had oral sex with another woman, but in neither group did the cumulative percent reach 50% by the age of 29 years and the median could not be estimated. Gay and bisexual men reported earlier receptive anal sex debut than heterosexual men. With regard to insertive anal sex, gay and bisexual men accumulated experience earlier than heterosexual men, and lesbian and bisexual women acquired this experience earlier than heterosexual women. Compared to heterosexuals, LGB persons of both genders engage in more varied sexual activities. Lesbian and gay persons have same-sex experiences at an earlier age than bisexuals.

• Finnes, Trine Elisabeth; Lofthus, Cathrine Marie; Meyer, Haakon E; Søgaard, Anne-Johanne; Tell, Grethe Seppola & Apalset, Ellen M [Show all 12 contributors for this article] (2016). A combination of low serum concentrations of vitamins K1 and D is associated with increased risk of hip fractures in elderly Norwegians: a NOREPOS study. Osteoporosis International. ISSN 0937-941X. 27(4), p. 1645–1652. doi: 10.1007/s00198-015-3435-0.
• Holvik, Kristin; Ahmed, Luai Awad; Forsmo, Siri; Gjesdal, Clara Gram; Grimnes, Guri & Samuelsen, Sven Ove [Show all 10 contributors for this article] (2015). No increase in risk of hip fracture at high serum retinol concentrations in community-dwelling older Norwegians: the Norwegian Epidemiologic Osteoporosis Studies. American Journal of Clinical Nutrition. ISSN 0002-9165. 102(5), p. 1289–1296. doi: 10.3945/ajcn.115.110528.
• Stenehjem, Jo Steinson; Kjærheim, Kristina; Bråtveit, Magne; Samuelsen, Sven Ove; Barone-Adesi, Francesco & Rothman, Nathaniel [Show all 8 contributors for this article] (2015). Benzene exposure and risk of lymphohaematopoietic cancers in 25 000 offshore oil industry workers. British Journal of Cancer. ISSN 0007-0920. 112(9), p. 1603–1612. doi: 10.1038/bjc.2015.108. Full text in Research Archive
• Holvik, Kristin; Gjesdal, Clara Gram; Tell, Grethe Seppola; Grimnes, Guri; Schei, Berit & Apalset, Ellen M [Show all 10 contributors for this article] (2014). Low serum concentrations of alpha-tocopherol are associated with increased risk of hip fracture. A NOREPOS study. Osteoporosis International. ISSN 0937-941X. 25(11), p. 2545–2554. doi: 10.1007/s00198-014-2802-6.
• Finnes, Trine Elisabeth; Lofthus, Cathrine Marie; Meyer, Haakon E.; Eriksen, Erik Fink; Apalset, Ellen M & Tell, Grethe S [Show all 9 contributors for this article] (2014). Procollagen type 1 amino-terminal propeptide (P1NP) and risk of hip fractures in elderly Norwegian men and women. A NOREPOS study. Bone. ISSN 8756-3282. 64, p. 1–7. doi: 10.1016/j.bone.2014.03.010. Show summary

  The current study aimed to assess a possible association between the bone turnover marker procollagen type 1 amino-terminal propeptide (P1NP) and future hip fractures in elderly Norwegian men and women and to elucidate the relation between P1NP, bone mineral density and 25-hydroxyvitamin D (25(OH)D). Men and women aged 71 to 77 from two population based health studies in Norway (1999-2001) were followed for a median period of 7.3years with respect to hip fractures. The study was designed as a case-cohort study. P1NP and 25(OH)D were analysed in frozen serum samples obtained at baseline in hip fracture patients (n=340) and in randomly selected sex stratified sub-cohorts. Bone mineral density was measured by dual-energy X-ray absorptiometry (DXA) in a subset of participants. Cox proportional hazards regression with inverse probability weighting and robust variance was performed. No significant correlation between 25(OH)D and P1NP was found. A negative correlation between P1NP and BMD was observed in women (Rho=-0.36, p=0.001). A similar trend was observed in men. No association between quartiles of P1NP and rate of subsequent hip fractures was found. Spline analyses suggested a higher rate of hip fracture at P1NP levels above 60μg/L in both men and women. A higher hip fracture rate, which was independent of BMD, was also indicated in women with very low levels of P1NP.

• Vikanes, Åse Vigdis; Støer, Nathalie; Gunnes, Nina; Grjibovski, Andrej; Samuelsen, Sven Ove & Magnus, Per [Show all 7 contributors for this article] (2013). Helicobacter pylori infection and severe hyperemesis gravidarum among immigrant women in Norway: a case–control study. European Journal of Obstetrics, Gynecology, and Reproductive Biology. ISSN 0301-2115. 167(1), p. 41–46. doi: 10.1016/j.ejogrb.2012.11.007.
• Støer, Nathalie & Samuelsen, Sven Ove (2013). Inverse probability weighting in nested case-control studies with additional matching-a simulation study. Statistics in Medicine. ISSN 0277-6715. 32(30), p. 5328–5339. doi: 10.1002/sim.6019.
• Borgan, Ørnulf & Samuelsen, Sven Ove (2013). Nested Case-Control and Case-Cohort Studies. In Klein, John P; van Houwelingen, Hans C; Ibrahim, Joseph G & Scheike, Thomas H (Ed.), Handbook of Survival Analysis. CRC Press. ISSN 9781466555662. p. 343–367.
• Holvik, Kristin; Ahmed, Luai Awad; Forsmo, Siri; Gjesdal, Clara Gram; Grimnes, Guri & Samuelsen, Sven Ove [Show all 10 contributors for this article] (2013). Low Serum Levels of 25-Hydroxyvitamin D Predict Hip Fracture in the Elderly: A NOREPOS Study. Journal of Clinical Endocrinology and Metabolism (JCEM). ISSN 0021-972X. 98(8), p. 3341–3350. doi: 10.1210/jc.2013-1468. Full text in Research Archive
• Haavaldsen, Camilla; Samuelsen, Sven Ove & Eskild, Anne (2013). Fetal death and placental weight/birthweight ratio: a population study. Acta Obstetricia et Gynecologica Scandinavica. ISSN 0001-6349. 92(5), p. 583–590. doi: 10.1111/aogs.12105.
• Håberg, Siri Eldevik; Trogstad, Lill; Gunnes, Nina; Wilcox, AJ; Gjessing, Håkon K. & Samuelsen, Sven Ove [Show all 19 contributors for this article] (2013). Risk of Fetal Death after Pandemic Influenza Virus Infection or Vaccination. New England Journal of Medicine. ISSN 0028-4793. 368(4), p. 333–340. doi: 10.1056/NEJMoa1207210.
• Ahmad, Aahshi Ambareen Sarfraz & Samuelsen, Sven Ove (2012). Hypertensive disorders in pregnancy and fetal death at different gestational lengths: a population study of 2 121 371 pregnancies. BJOG: An International Journal of Obstetrics and Gynaecology. ISSN 1470-0328. 119(12), p. 1521–1528. doi: 10.1111/j.1471-0528.2012.03460.x.
• Samuelsen, Sven Ove & Veierød, Marit Bragelien (2012). Poisson regression. In Veierød, Marit Bragelien; Lydersen, Stian & Laake, Petter (Ed.), Medical statistics in clinical and epidemiological research. Gyldendal Akademisk. ISSN 9788205399594. p. 200–230.
• Støer, Nathalie & Samuelsen, Sven Ove (2012). Comparison of estimators in nested case-control studies with multiple outcomes. Lifetime Data Analysis. ISSN 1380-7870. 18(3), p. 261–283. doi: 10.1007/s10985-012-9214-8.
• Gjerde, Hallvard; Christophersen, Asbjørg S; Normann, Per Trygve; Pettersen, Bjørg Sjøgren; Sabaredzovic, Azemira & Samuelsen, Sven Ove [Show all 7 contributors for this article] (2012). Analysis of Alcohol and Drugs in Oral Fluid From Truck Drivers in Norway. Traffic Injury Prevention. ISSN 1538-9588. 13(1), p. 43–48. doi: 10.1080/15389588.2011.627957.
• Gulsvik, Anne Kristine; Thelle, Dag Steinar; Samuelsen, Sven Ove; Myrstad, Marius; Mowe, Morten & Wyller, Torgeir Bruun (2012). Ageing, physical activity and mortality - a 42-year follow-up study. International Journal of Epidemiology. ISSN 0300-5771. 41(2), p. 521–530. doi: 10.1093/ije/dyr205.
• Haavaldsen, Marit Camilla; Samuelsen, Sven Ove & Eskild, Anne (2011). The association of maternal age with placental weight: a population-based study of 536 954 pregnancies. BJOG: An International Journal of Obstetrics and Gynaecology. ISSN 1470-0328. 118(12), p. 1470–1476. doi: 10.1111/j.1471-0528.2011.03053.x.
• Gjerde, Hallvard; Normann, Per Trygve; Christophersen, Asbjørg S.; Samuelsen, Sven Ove & Mørland, Jørg (2011). Alcohol, psychoactive drugs and fatal road traffic accidents in Norway: A case-control study. Accident Analysis and Prevention. ISSN 0001-4575. 43(3), p. 1197–1203. doi: 10.1016/j.aap.2010.12.034.
• Sarfraz, Aahshi Ambareen; Samuelsen, Sven Ove & Eskild, Anne (2011). Changes in fetal death during 40 years-different trends for different gestational ages: a population-based study in Norway. BJOG: An International Journal of Obstetrics and Gynaecology. ISSN 1470-0328. 118(4), p. 488–494. doi: 10.1111/j.1471-0528.2010.02819.x.
• Stigum, Hein; Samuelsen, Sven Ove & Træen, Bente (2010). Analysis of first coitus. Archives of Sexual Behavior. ISSN 0004-0002. 39(4), p. 907–914. doi: 10.1007/s10508-009-9494-6.
• Vikanes, Åse Vigdis; Grjibovski, Andrej; Vangen, Siri; Gunnes, Nina; Samuelsen, Sven Ove & Magnus, Per (2010). Maternal body composition, smoking, and hyperemesis gravidarum. Annals of Epidemiology. ISSN 1047-2797. 20(8), p. 592–598. doi: 10.1016/j.annepidem.2010.05.009.
• Haavaldsen, Marit Camilla; Sarfraz, Aahshi Ambareen; Samuelsen, Sven Ove & Eskild, Anne (2010). The impact of maternal age on fetal death: does length of gestation matter? American Journal of Obstetrics and Gynecology. ISSN 0002-9378. 203(6), p. 554.e1–554.e8. doi: 10.1016/j.ajog.2010.07.014.
• Småstuen, Milada C; Samuelsen, Sven Ove; Magelssen, Henriette & Fosså, Sophie Dorothea (2009). Reproduction Rates After Cancer Treatment: Experience From the Norwegian Radium Hospital. Journal of Clinical Oncology. ISSN 0732-183X. 27(3), p. 334–343. doi: 10.1200/JCO.2007.15.3130.
• Brantsæter, Anne Lise; Haugen, Margaretha; Samuelsen, Sven Ove; Torjusen, Hanne; Trogstad, Lill-Iren Schou & Alexander, Jan [Show all 8 contributors for this article] (2009). A dietary pattern characterized by high intake of vegetables, fruits, and vegetable oils is associated with reduced risk of preeclampsia in nulliparous pregnant Norwegian Women. Journal of Nutrition. ISSN 0022-3166. 139(6), p. 1162–1168. doi: 10.3945/jn.109.104968.
• Samuelsen, Sven Ove; Bakketeig, Leiv Sigmund; Tretli, Steinar; Johannesen, Tom B & Magnus, Per (2009). Birth weight and childhood cancer. Epidemiology. ISSN 1044-3983. 20(4), p. 484–487. doi: 10.1097/EDE.0b013e3181a7786d.
• Rasmussen, Trond; Stene, Lars Christian; Samuelsen, Sven Ove; Cinek, Ondrej; Wetlesen, Turid Bjørnstad & Torjesen, Peter A [Show all 7 contributors for this article] (2009). Maternal BMI before pregnancy, maternal weight gain during pregnancy, and risk of persistent positivity for multiple diabetes-associated autoantibodies in children with the high-risk HLA genotype: the MIDIA study. Diabetes Care. ISSN 0149-5992. 32(10), p. 1904–1906. doi: 10.2337/dc09-0663.
• Sarfraz, AA; Samuelsen, Sven Ove; Bruu, AL; Jenum, PA & Eskild, Anne (2009). Maternal human parvovirus B19 infection and the risk of fetal death and low birthweight: a case-control study within 35 940 pregnant women. BJOG: An International Journal of Obstetrics and Gynaecology. ISSN 1470-0328. 116(11), p. 1492–1497. doi: 10.1111/j.1471-0528.2009.02211.x.
• Olsen, AL; Johannesen, TB; Ly, Bernt Erik; Samuelsen, Sven Ove; Tjønnfjord, Geir Erland & Jønsson, Viggo (2008). Pleiotropy in families with chronic lymphocytic leukemia. Salud (i) Ciencia. ISSN 1667-8982. 15, p. 1236–+.
• Jønsson, Viggo; Tjønnfjord, Geir Erland; Johannesen, T.B.; Samuelsen, Sven Ove & Ly, Bernt Erik (2008). Possible Imprinting and Microchimerism in Chronic Lymphocytic Leukemia and Related Lymphoproliferative Disorders. Translational Oncogenomics. ISSN 1177-2727. 3, p. 1–6.
• Samuelsen, Sven Ove & Eide, Geir Egil (2008). Attributable fractions with survival data. Statistics in Medicine. ISSN 0277-6715. 27(9), p. 1447–1467. doi: 10.1002/sim.3022.
• Eberhard-Gran, Malin M C; Eskild, Anne; Samuelsen, Sven Ove & Tambs, Kristian (2007). A short matrix-version of the Edinburgh Depression Scale. Acta Psychiatrica Scandinavica. ISSN 0001-690X. 116(3), p. 195–200. doi: 10.1111/j.1600-0447.2006.00934.x.
• Brantsæter, Anne Lise; Haugen, Alice Margaretha; Rasmusen, Salka E; Alexander, Jan; Samuelsen, Sven Ove & Meltzer, Helle Margrete (2007). Urine flavonoids and plasma carotenoids in the validation of fruit, vegetable and tea intake during pregnancy in the Norwegian Mother and Child Cohort Study (MoBa). Public Health Nutrition (PHN). ISSN 1368-9800. 10(8), p. 838–847. doi: 10.1017/S1368980007339037.
• Samuelsen, Sven Ove; Anestad, H & Skrondal, A (2007). Stratified case-cohort analysis of general cohort sampling designs. Scandinavian Journal of Statistics. ISSN 0303-6898. 34. doi: 10.1111/j.1467-9469.2006.00552.x.
• Jønsson, Viggo; Tjønnfjord, Geir Erland; Samuelsen, Sven Ove; Johannesen, Tom; Olsen, Jørgen & Sellick, Gabrielle [Show all 9 contributors for this article] (2007). Birth order pattern in the inheritance of chronic lymphocytic leukaemia and related lymphoproliferative disease. Leukemia and Lymphoma. ISSN 1042-8194. 48(12), p. 2387–2396. doi: 10.1080/10428190701686273.
• Aamodt, Geir; Samuelsen, Sven Ove & Skrondal, Anders (2006). A simulation study of three methods for detecting disease clusters. International Journal of Health Geographics. ISSN 1476-072X. 5(15). doi: 10.1186/1476-072X-5-15.
• Pedersen, Willy; Eskild, Anne & Samuelsen, Sven Ove (2006). Abort hos unge kvinner - betydningen av oppvekst og sosial klasse. Tidsskrift for Den norske legeforening. ISSN 0029-2001. 126(13-14), p. 1734–1737.
• Arntzen, Annett; Samuelsen, SO; Daltveit, Anne Kjersti Nesje & Stoltenberg, Camilla (2006). Post-neonatal mortality in Norway 1969-95: a cause-specific analysis. International Journal of Epidemiology. ISSN 0300-5771. 35(4), p. 1083–1089. doi: 10.1093/ije/dyl047.
• Samuelsen, Sven Ove; Bakketeig, Leiv Sigmund; Tretli, Steinar; Johannesen, Tom B & Magnus, Per (2006). Head circumference at birth and risk of brain cancer in childhood: a population-based study. The Lancet Oncology. ISSN 1470-2045. 7(1), p. 39–42. doi: 10.1016/S1470-2045(05)70470-8.
• Nystad, Wenche; Samuelsen, Sven Ove; Nafstad, Per & Langhammer, A (2006). Association between level of physical activity and lung function among Norwegian men and women: the HUNT study. The International Journal of Tuberculosis and Lung Disease. ISSN 1027-3719. 10(12), p. 1399–1405.
• Arntzen, Annett; Samuelsen, Sven Ove; Bakketeig, Leiv S & Stoltenberg, Camilla (2005). A. Arntzen og medarbeidere svarer:. Tidsskrift for Den norske legeforening. ISSN 0029-2001. 125(Årg. 125, nr 3).
• Eggesbø, Merete; Botten, Grete Synøve; Stigum, Hein; Samuelsen, Sven Ove; Brunenkreef, B & Magnus, Per (2005). Cesarean delivery and cow milk allergy/intolerance. Allergy. European Journal of Allergy and Clinical Immunology. ISSN 0105-4538. 60, p. 1172–1173.
• Nafstad, Per; Samuelsen, Sven Ove; Samuelsen, S; Irgens, Lorentz M. & Bjerkedal, Tor (2005). Svangerskapskomplikasjoner og risikoen for astma blant nordmenn født 1967-1993. Norsk Epidemiologi. ISSN 0803-2491. 15(1), p. 47–54.
• Samuelsen, Sven Ove; Wisløff, TF & Skrondal, Anders (2005). A simple correction for ties when censoring times depend on covariates. Statistics in Medicine. ISSN 0277-6715. 24(20), p. 3111–3121. Show summary

  We point out that the conventional methods for ties correction may be seriously biased when censoring times depend on covariates. A simple modification to the Efron correction method is suggested which works remarkably well in simulation studies. The method Corresponds closely to breaking ties by random ordering. The modified correction method is easy to implement and computationally no more demanding than the Efron correction.

• Eggesbø, Merete Åse; Botten, G; Stigum, Hein; Samuelsen, Sven Ove; Breunekreef, B & Magnus, Per (2005). Cesarean delivery and cow milk allergy/intolerance. Allergy. European Journal of Allergy and Clinical Immunology. ISSN 0105-4538. 60(9), p. 1172–1173. doi: 10.1111/j.1398-9995.2005.00857.x.
• Nafstad, Per; Samuelsen, Sven Ove; Irgens, Lorentz M & Bjerkedal, Tor (2005). Svangerskapskomplikasjoner og risikoen for astma blant nordmenn født 1967-1993. Norsk Epidemiologi. ISSN 0803-2491. 15(1), p. 47–54.
• Samuelsen, Sven Ove; Wisløff, Torbjørn Fosen & Skrondal, Anders (2005). A simple correction for ties when censoring times depend on covariates. Statistics in Medicine. ISSN 0277-6715. 24(20), p. 3111–3121. doi: 10.1002/sim.2173.
• Arntzen, Annett; Samuelsen, Sven Ove; Bakketeig, Leiv S & Stoltenberg, Camilla (2004). Foreldres utdanning og spedbarnsdødelighet 1967-98. Tidsskrift for Den norske legeforening. ISSN 0029-2001. 124(Årg. 124, nr 22), p. 2904–2906.
• Arntzen, Annett; Samuelsen, Sven Ove; Bakketeig, Leiv S & Stoltenberg, Camilla (2004). Foreldres utdanning og spedbarnsdødelighet 1967?98. ?. 124(22), p. 2904–2906. Show summary

  Bakgrunn. Vi har analysert sammenhengen mellom spedbarnsdødelighet og foreldres utdanningsnivå i perioden 1967 - 98 for å finne ut om det har skjedd en sosial utjevning eller ikke. Materiale og metode. Studien omfatter alle 1 777 364 levendefødte barn i perioden 1967 - 98. Data fra Medisinsk fødselsregister er koblet til Dødsårsaksregisteret og Utdanningsregisteret. Fødslene er delt i tre perioder: 1967 - 79, 1980 - 89 og 1990 - 98. Utdanning er gruppert som lav (< 10 år), middels (10 - 12 år) og høy (> 12 år). Forskjeller i dødelighet mellom utdanningsgruppene er estimert som risikodifferanser, relativ risiko, tilskrivbar risiko og indeks for relativ ulikhet. Resultater. I perioden 1967 - 1998 falt spedbarnsdødeligheten i alle utdanningsgrupper, og utdanningsnivået økte betraktelig. I første levemåned var forskjellen i dødelighet forbarn av mødre med høy og lav utdanning 3,5/1 000 på 1970-tallet, og 0,9/1 000 på 1990-tallet, mens tilskrivbar risiko faltfra 22,3 % til 8,4 %. For resten av første leveår (28 - 364dager) økte forskjellen i dødelighet mellom høyeste og lavesteutdanningsgruppe fra 0,7/1 000 på 1970-tallet til 2,0/1 000 på 1990-tallet. I samme periode økte tilskrivbar risiko fra9,7 % til 39,5 %. Fortolkning. Den sosiale ulikheten er utjevnet for dødeligheten i første levemåned. For resten av første leveår har de sosiale forskjellene økt.

• Arntzen, Annett; Samuelsen, Sven Ove & Bakketeig, Leiv S (2004). Socioeconomic status and risk of infant death : a population-based study of trends in Norway, 1967?1998. International Journal of Epidemiology. ISSN 0300-5771. 33(2), p. 279–288. Show summary

  Background The aim of this study was to examine the association between socioeconomic status and risk of infant death in Norway from 1967 to 1998. Methods Information from the Medical Birth Registry of Norway on all live births and infant deaths was linked to information from Statistics Norway on parents' education. There were 1 777 364 eligible live births and 15 517 infant deaths. Differences between education groups were estimated as risk differences, relative risks, population attributable fractions, and index of inequality ratios. Results The risk of infant death decreased in all education groups, and the level of education increased over time. The trends differed for neonatal and postneonatal death. For neonatal death the risk difference between infants whose mothers had high and low education was reduced from 3.5/1000 in the 1970s to 0.9/1000 in the 1990s. The relative index of inequality (RII) for maternal education decreased from 1.72 to1.32. The proportion of neonatal deaths that could be attributed to <13 years of education decreased from 22.3 to 8.4. For postneonatal death the risk difference between infants whose mothers hadhigh and low education increased from 0.7/1000 in the 1970s to 2.0/1000 in the 1990s. The RII for maternal education increased from 1.31 to 4.00. The population attributable fractionincreased from 9.7 to 39.5. Conclusions An inverse association between socioeconomic status and risk of postneonatal death persists, albeit there was a considerable reduction in riskbetween 1967 and 1998.

• Arntzen, Annett; Samuelsen, Sven Ove; Bakketeig, Leiv S & Stoltenberg, Camilla (2004). Socioeconomic status and risk of infant death. A population-based study of trends in Norway, 1967-1998. International Journal of Epidemiology. ISSN 0300-5771. 33, p. 279–288. Show summary

  Conclusions An inverse association between socioeconomic status and risk of postneonatal death persists, albeit there was a considerable reduction in risk between 1967 and 1998.

• Samuelsen, Sven Ove; Stene, LC & Bakketeig, LS (2004). Association of head circumference at birth among sibling pairs. Paediatric and Perinatal Epidemiology. ISSN 0269-5022. 18, p. 26–32.
• Arntzen, Annett; Samuelsen, Sven Ove; Bakketeig, LC & Stoltenberg, Camilla (2004). Socioeconomic status and risk of infant death. A population-based study of trends in Norway, 1967-1998. International Journal of Epidemiology. ISSN 0300-5771. 33, p. 279–288.
• Arntzen, Annett; Samuelsen, Sven Ove; Bakketeig, LS & Stoltenberg, Camilla (2004). Sosial ulikhet og spedbarnsdødelighet. En befolkningsbasert studie om sammenhengen mellom foreldres utdanning og spedbarnsdødelighet i perioden 1967-1998. Tidsskrift for Den norske legeforening. ISSN 0029-2001. 124, p. 2904–2906.

View all works in Cristin

• Samuelsen, Sven Ove & Aalen, Odd O. (2023). Special issue dedicated to Ørnulf Borgan. Lifetime Data Analysis. ISSN 1380-7870. 29(2), p. 253–255. doi: 10.1007/s10985-023-09592-w.
• Finnes, Trine Elisabeth; Lofthus, Cathrine Marie; Søgaard, Anne-Johanne; Tell, Grethe Seppola; Apalset, Ellen M & Gjesdal, Clara Gram [Show all 12 contributors for this article] (2015). Low serum vitamin K1 increases the risk of hip fractures only at low vitamin D status. A NOREPOS study. European Geriatric Medicine. ISSN 1878-7649. 6, p. S17–S17.
• Midtervoll, Ingvild K.; Enersen, Morten; Kristoffersen, Anne Karin; Samuelsen, Sven Ove; Olsen, Ingar & Håheim, L.L. (2014). Detection of Periodontal Pathogens in Blood from Patients with Cardiovascular Disease. Poster presentation.
• Midtervoll, Ingvild K.; Enersen, Morten; Kristoffersen, Anne Karin; Samuelsen, Sven Ove & Lund Håheim, Lise (2014). Detection of Periodontal Pathogens in Blood from Patients With Cardiovascular Disease. Oral Presentation.
• Støer, Nathalie; Meyer, Haakon E & Samuelsen, Sven Ove (2014). Reuse of controls in nested case-control studies. Epidemiology. ISSN 1044-3983. 25(2), p. 315–317. doi: 10.1097/EDE.0000000000000057.
• Holvik, Kristin; Gjesdal, Clara Gram; Tell, Grethe S; Grimnes, Guri; Schei, Berit & Apalset, Ellen M [Show all 10 contributors for this article] (2013). Low serum concentrations of vitamin E are associated with increased risk of hip fracture in older Norwegians. A NOREPOS study. Norsk Epidemiologi, Supplement. ISSN 0803-4206. 23. Show summary

  Aim: We aimed to study the association between α-tocopherol concentrations in serum and risk of hip fractures in older men and women. Methods: In the Norwegian Epidemiologic Osteoporosis Studies (NOREPOS) we performed a case-cohort analysis in 21,774 men and women aged 65-79 years (mean 72 y) who underwent baseline examinations in four community-based health studies during 1994-2001. Data on incident hip fractures were retrieved from electronic patient administrative systems. Frozen serum samples from baseline were analyzed in participants who suffered a hip fracture during median 8.2 years of follow-up (n=1168) and in sex-stratified random samples from baseline (n=1434). α-tocopherol was determined by high pressure liquid chromatography (HPLC)-fluorescence detection. Cox proportional hazards regression adapted for the case-cohort design was performed with adjustment for age, sex, and study center. Results: We observed a linear inverse relation between serum α-tocopherol levels and hip fracture, with hazard ratio (HR) 1.11 (95% CI 1.04-1.20) per 10 µmol/l lower serum α-tocopherol. HR of hip fracture in the lowest (<22.6 µmol/l) compared with the highest (>=38.3 µmol/l) quartile of serum α-tocopherol was 1.51 (95% CI 1.17-1.95). Adjustment for serum concentrations of 25(OH)D and retinol, smoking, month of blood sample, body mass index, education, physical inactivity and self-rated health yielded similar results. Conclusion: Low serum concentrations of α-tocopherol were associated with increased risk of hip fracture in older Norwegian men and women.

• Håberg, Siri Eldevik; Trogstad, Lill; Gunnes, Nina; Wilcox, Allen J; Gjessing, Håkon K. & Samuelsen, Sven Ove [Show all 19 contributors for this article] (2013). Risk of Fetal Death After Pandemic Influenza Virus Infection or Vaccination EDITORIAL COMMENT. Obstetrical and Gynecological Survey. ISSN 0029-7828. 68(5), p. 348–349. doi: 10.1097/01.ogx.0000430377.29993.2b.
• Midtervoll, Ingvild K.; Kristoffersen, Anne Karin; Enersen, Morten; Samuelsen, Sven Ove & Lund Håheim, Lise (2013). PERIODONTAL PATHOGENS – A POSSIBLE ROLE IN CARDIOVASCULAR DISEASE? Show summary

  Objective: The aim of this ongoing study is to investigate a possible role for periodontal pathogens in relation to cardiovascular disease (CVD) through detection of bacterial DNA in bloodsamples from participants of the Oslo II study. Materials and methods: The study design is a blinded case-cohort design where the cohort is men from Oslo, born between 1926 and 1932. The test group consists of 225 individuals who have died from CVD (myocardial infarction, aortic aneurysms or stroke), and the control group are 225 healthy men randomly picked from the cohort. After DNA extraction from blood samples in both groups, PCR amplification of the 16S rRNA bacterial gene will be performed, and PCR products of 650bp fragment will be verified on a 1,5% agarose gel. Bacterial species will be detected by high throughput sequencing of the PCR products, and results from test and control group will be correlated. Furthermore, results from three diagnoses in the test group will also be correlated separately to the controls. Correction for known risk factors such as smoking, physical inactivity, high blood pressure, total serum cholesterol and diabetes will be performed. Results: Preliminary results from PCR amplification of 260 blinded bloodsamples indicate bacterial DNA detection with the expected fragment size in 124 (48%) of the samples investigated so far.

• Håberg, Siri Eldevik; Trogstad, Lill; Gunnes, Nina; Gjessing, Håkon K.; Samuelsen, Sven Ove & Cappelen, Inger [Show all 17 contributors for this article] (2012). The 2009 Influenza Pandemic, Vaccination during Pregnancy and Fetal Death: A National Registry-Based Study in Norway. Pharmacoepidemiology and Drug Safety. ISSN 1053-8569. 21, p. 382–382.
• Vikanes, Åse Vigdis; Grjibovski, Andrej; Gunnes, Nina; Magnus, Per; Haugen, Margaretha & Støer, Nathalie [Show all 12 contributors for this article] (2012). Hyperemesis gravidarum - what is new? Highlights from seven Norwegian epidemiological studies. Acta Obstetricia et Gynecologica Scandinavica. ISSN 0001-6349. 91, p. 141–141.
• Arntzen, Annett; Samuelsen, Sven Ove; Vangen, Siri & Stoltenberg, Camilla (2012). Have immigrants in Norway higher risk of stillbirth and infant mortality? European Journal of Public Health. ISSN 1101-1262. 22(supp. 2), p. 10–11.
• Holvik, Kristin; Ahmed, Luai A.; Blomhoff, Rune; Forsmo, Siri; Gjesdal, Clara Gram & Grimnes, Guri [Show all 10 contributors for this article] (2012). Vitamin D status in home-dwelling elderly across Norway and prospective risk of hip fracture. A case-cohort study within the Norwegian Epidemiologic Osteoporosis Studies (NOREPOS).
• Holvik, Kristin; Ahmed, Luai A.; Blomhoff, Rune; Forsmo, Siri; Gjesdal, Clara Gram & Grimnes, Guri [Show all 10 contributors for this article] (2012). Vitamin D status and the risk of hip fracture in elderly in Norway. A four-center case-cohort study within the Norwegian Epidemiologic Osteoporosis Studies (NOREPOS). Show summary

  Objective: The relationship between vitamin D status and risk of hip fracture has not been established. Our aim was to study this relationship in a population-based case-cohort study of elderly men and women in Norway. Methods: N=21,774 men and women aged 65-79 years attended baseline examinations in four population-based health studies in Norway during 1994-2001. Subsequent hip fractures were retrieved from patient administrative systems and verified by X-ray or medical records, with maximum follow-up 10.7 years. All hip fracture cases and randomly sampled gender-specific subcohorts of men (4.5% yielding n=444) and women (9.0% yielding n=1058) were selected for analysis of 25-hydroxyvitamin D (25(OH)D) in serum samples from baseline stored at −80°C. 25(OH)D2 and 25(OH)D3 was determined by HPLC-APCI-MS. We performed Cox proportional hazards regression of hip fracture vs. quartiles of total 25(OH)D, with left-truncation for age at baseline and right-censoring for age at exit, inverse probability weighting and robust variance, adjusted for study site. Additional analyses were adjusted for season of blood sample, body mass index, daily cigarette smoking, and self-rated health. Results: During a median follow-up of 8.2 years, 1232 individuals (340 men (3.4%) and 892 women (7.5%)) sustained a hip fracture. The subcohorts included 1502 individuals of whom 93 were also cases. Intact frozen serum was available and successfully analysed in n=2526 (95.6%). In men, there was a trend of increasing risk of hip fracture with decreasing 25(OH)D, statistically significant for Q1 (<43.3 nmol/l) vs. Q4 (>=69.2 nmol/l): HR 1.68 (95% CI 1.05-2.68) in the main analysis, and HR 1.65 (95% CI 1.01-2.67) in the fully adjusted analysis. In women, there was no significant relation between 25(OH)D and hip fracture. However, there was a tendency of increased HR in decreasing quartiles of 25(OH)D in adjusted analysis, with HR 1.19 (95% CI 0.90-1.59) in Q1 (<41.5 nmol/l) vs. Q4 (>=67.0 nmol/l). Conclusion: According to these preliminary analyses, lower vitamin D status was significantly associated with increased HR of hip fracture in men, but not women.

• Holvik, Kristin; Samuelsen, Sven Ove; Ahmed, Luai Awad; Forsmo, Siri; Gjesdal, Clara Gram & Grimnes, Guri [Show all 10 contributors for this article] (2012). Low serum levels of vitamins D and A predict hip fracture in the elderly. A multicenter case-cohort study within the Norwegian Epidemiologic Osteoporosis Studies (NOREPOS). Show summary

  Background: Norwegians have among the highest hip fracture rates worldwide. Vitamin D status is generally good and vitamin A intake is relatively high in Norway. Increased fracture risk at high intakes and serum levels of retinol have been observed in earlier epidemiologic studies. Objective: To study whether serum concentration of vitamins D and A in elderly Norwegians are related to risk of hip fracture, and whether high serum vitamin A (retinol) may counteract a possible protective effect of vitamin D. Methods: N=21,774 men and women aged 65-79 attended four community-based health studies during 1994- 2001. Subsequent hip fractures were retrieved from hospitals’ patient administrative systems, with maximum follow-up 10.7 years. 25(OH)D was determined by HPLC-APCI-MS and retinol by HPLC-UV in baseline serum samples in cases and weighted random samples of men and women. Adjusted Cox proportional hazards regression modified for the case-cohort design was performed using R. Results: During median follow-up 8.2 years, 340 men (3.4%) and 892 women (7.5%) suffered a hip fracture. We found an inverse association between 25(OH)D and hip fracture; HR 1.35 (95% CI 1.07-1.70) for <50 nmol/l compared with >75 nmol/l. Compared with middle retinol levels (2-3 μmol/l), low levels (<2 μmol/l) was associated with increased hip fracture risk: HR 1.27 (95% CI 1.00-1.62). In stratified analyses, the inverse association between 25(OH)D and risk of hip fracture was apparent at low retinol levels in men, but only at high retinol levels in women. Conclusion: Both 25(OH)D and retinol were inversely associated with risk of hip fracture.

• Vikanes, Åse Vigdis; Stoer, NC; Gunnes, Nina; Grjibovski, Andrei M.; Samuelsen, Sven Ove & Magnus, Per [Show all 7 contributors for this article] (2012). Helicobacter pylori and severe hyperemesis gravidarum by IgG, virulence factors and feces antigens; an institution-based case-control study among immigrant women in Norway. European Journal of Public Health. ISSN 1101-1262. 22, p. 240–240.
• Haavaldsen, Camilla; Sarfraz, Aahshi Ambareen; Samuelsen, Sven Ove & Eskild, Anne (2011). The Impact of Maternal Age on Fetal Death: Does Length of Gestation Matter? Obstetrical and Gynecological Survey. ISSN 0029-7828. 66(4), p. 185–186. doi: 10.1097/OGX.0b013e3182114936.
• Aamodt, Geir; Søgaard, Anne-Johanne; Næss, Øyvind Erik; Beckstrøm, Anne Cathrine & Samuelsen, Sven Ove (2010). CONOR-databasen - et lite stykke Norge. Tidsskrift for Den norske legeforening. ISSN 0029-2001. 130(3), p. 264–265.
• Cvancarova, Milada; Samuelsen, Sven Ove & Fosså, Sophie Dorothea (2009). Reproduction Rates After Cytotoxic Therapy Reply. Journal of Clinical Oncology. ISSN 0732-183X. 27(27), p. E120–E120. doi: 10.1200/JCO.2009.23.5895.
• Johannesen, Tom Børge; Ly, Bernt Erik; Samuelsen, Sven Ove; Tjønnfjord, Geir Erland & Jønsson, Viggo (2008). Ny studie om kronisk lymfatisk leukemi i Norge. Tidsskrift for Den norske legeforening. ISSN 0029-2001. 128(6).
• Jønsson, Viggo; Samuelsen, Sven Ove; Tjønnfjord, Geir Erland & johannesen, tom (2008). Looking for CLL genes. Leukemia and Lymphoma. ISSN 1042-8194. 49, p. 10–11. doi: 10.1080/10428190701713705.
• Jønsson, Viggo; Tjønnfjord, Geir Erland; Samuelsen, Sven Ove; Johannesen, Tom & Ly, Bernt (2007). Pleiotrophy in familial CLL. Leukemia and Lymphoma. ISSN 1042-8194. 48.
• Eberhard-Gran, Malin ; Eskild, Anne; Samuelsen, SO & Tambs, K (2007). A short matrix-version of the Edinburgh Postnatal Depression Scale.
• Arntzen, Annett; Samuelsen, Sven Ove; Bakketeig, Leiv S & Stoltenberg, Camilla (2004). Long term trends in social inequalities in infant death in Norway : going in the right direction, but still s way to go.
• Nordby, Katrine & Samuelsen, Sven Ove (2020). Dødelighet ved hoftebrudd: Analyser av kohort og matchet kohort data. Universitetet i Oslo. Show summary

  Hoftebrudd innebærer brudd i lårhalsen eller i området ved den lille og store lårbensknuten. Vi vet at 70% av individer med hoftebrudd er kvinner og også at 70% av disse individene er over 70 år. I denne oppgaven er vi interessert i dødeligheten ved hoftebrudd. Vi skal utføre en kohortstudie der vi analyserer et datasett bestående av individer som var 50 år eller eldre i folke- og boligtellingen i Norge i 2001. Vi vil gjøre diverse undersøkelser for å beskrive dødeligheten for ulike kovariater. I hovedsak er vi interessert i å undersøke hvordan diverse kovariater påvirker dødeligheten ved hoftebrudd. Store kohortanalyser kan være både tidkrevende og kostbare. Matchede kohortanalyser der vi ser på en submengde av kohorten er et alternativ for å få ned kostnadene og tiden det tar å utføre analysene. Vi skal i denne oppgaven også utføre matchede kohortanalyser der vi matcher eksponerte individer med ikke-eksponerte individer ved hjelp av gitte matchingsvariable. Vi er interessert i hvor stor submengde, eller mer presist hvor mange ikke-eksponerte individer vi trenger å matche hvert eksponert individ med for å oppnå omtrent like god presisjon i resultatene som ved den fulle kohorten.

• Johansen, Lena Rogstad & Samuelsen, Sven Ove (2018). Metoder og metodiske utfordringer for matchede kohortstudier. Universitetet i Oslo. Show summary

  Når man estimerer effekten av en bestemt behandling eller eksponering på utfall i kohortstudier, og observasjonsstudier generelt, gir ikke standard metoder korrekte resultater i nærvær av ukontrollert konfundering. Matching er en teknikk som korrigerer for dette. I denne oppgaven studerer vi først og fremst i hvilken grad det er mulig å analysere matchede (også kalt tilordnede) kohortstudier når man ignorerer matchingsvariablene (konfunderingsvariablene) under forskjellige modellforutsetninger. Vi ser også på hvor mange ikke-eksponerte individer man bør velge per eksponert individ. Det viser seg at den estimerte sammenhengen mellom eksponering og utfall i nærvær versus fravær av matchingsvariablene avhenger av modellen for levetidene. Ettersom denne er både ukjent og ukontrollerbar i virkeligheten bør man beholde matchingsvariablene i analysen, såfremt det er mulig. Dessuten synes det å være lite å vinne på å velge flere enn ti ikke-eksponerte individer per eksponert individ.

View all works in Cristin