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This study aimed to assess the impact of bariatric surgery on cancer risk in a multi-national setting.<\/jats:p>\n              <\/jats:sec><jats:sec>\n                <jats:title>Materials and Methods<\/jats:title>\n                <jats:p>This cohort study included all adults with an obesity diagnosis identified from national patient registries in all Nordic countries (Denmark, Finland, Iceland, Norway and Sweden) from 1980 to 2012. Cancer risk in bariatric surgery patients was compared with non-operated patients with obesity. Multivariable Cox regression provided adjusted hazard ratios (HRs) with 95% confidence intervals (CIs). Age, sex, calendar year, country, length of follow-up, diabetes, chronic obstructive pulmonary disease and alcohol-related diseases were evaluated as confounders.<\/jats:p>\n              <\/jats:sec><jats:sec>\n                <jats:title>Results<\/jats:title>\n                <jats:p>Among 482,572 participants with obesity, 49,096 underwent bariatric surgery. Bariatric surgery was followed by a decreased overall cancer risk in women (HR 0.86, 95% CI 0.80\u20130.92), but not in men (HR 0.98, 95% CI 0.95\u20131.01). The risk reduction was observed only within the first five post-operative years. Among specific tumours, HRs decreased for breast cancer (HR 0.81, 95% CI 0.69\u20130.95), endometrial cancer (HR 0.69, 95% CI 0.56\u20130.84) and non-Hodgkin lymphoma (HR 0.64, 95% CI 0.42\u20130.97) in female bariatric surgery patients, while the risk of kidney cancer increased in both sexes (HR 1.44, 95% CI 1.13\u20131.84).<\/jats:p>\n              <\/jats:sec><jats:sec>\n                <jats:title>Conclusion<\/jats:title>\n                <jats:p>Bariatric surgery may decrease overall cancer risk in women within the first five\u00a0years after surgery. This decrease may be explained by a decreased risk of breast and endometrial cancer and non-Hodgkin lymphoma in women.<\/jats:p>\n              <\/jats:sec>","DOI":"10.1007\/s11695-020-04751-6","type":"journal-article","created":{"date-parts":[[2020,6,13]],"date-time":"2020-06-13T20:02:32Z","timestamp":1592078552000},"page":"3761-3767","update-policy":"https:\/\/doi.org\/10.1007\/springer_crossmark_policy","source":"Crossref","is-referenced-by-count":46,"title":["Cancer Risk After Bariatric Surgery in a Cohort Study from the Five Nordic Countries"],"prefix":"10.1007","volume":"30","author":[{"given":"Wenjing","family":"Tao","sequence":"first","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Giola","family":"Santoni","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"My","family":"von Euler-Chelpin","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Rickard","family":"Ljung","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Elsebeth","family":"Lynge","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Eero","family":"Pukkala","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Eivind","family":"Ness-Jensen","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"P\u00e5l","family":"Romundstad","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Laufey","family":"Tryggvadottir","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-5143-5448","authenticated-orcid":false,"given":"Jesper","family":"Lagergren","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"297","published-online":{"date-parts":[[2020,6,13]]},"reference":[{"key":"4751_CR1","doi-asserted-by":"publisher","first-page":"794","DOI":"10.1056\/NEJMsr1606602","volume":"375","author":"B Lauby-Secretan","year":"2016","unstructured":"Lauby-Secretan B, Scoccianti C, Loomis D, et al. 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The study used individual level data from the registries in the Nordic countries. No endorsement by the authorities responsible for the registries is intended nor should be inferred.","order":3,"name":"Ethics","group":{"name":"EthicsHeading","label":"Disclaimer"}},{"value":"For this type of study, formal consent is not required. The study was approved by Ethical Review Boards and Data Inspectorates from all five Nordic countries.","order":4,"name":"Ethics","group":{"name":"EthicsHeading","label":"Ethical Approval Statement"}},{"value":"Informed consent does not apply. Waivers of informed consent are granted for register-based studies in all five Nordic countries.","order":5,"name":"Ethics","group":{"name":"EthicsHeading","label":"Informed Consent Statement"}}]}}