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Body mass index and risk of infections: a Mendelian randomization study of 101,447 individuals.

Authors
  • Winter-Jensen, Matilde1
  • Afzal, Shoaib2, 3
  • Jess, Tine1, 4
  • Nordestgaard, Børge G3, 5
  • Allin, Kristine H6, 7
  • 1 Center for Clinical Research and Prevention, Bispebjerg and Frederiksberg Hospital, The Capital Region, Nordre Fasanvej 57, 2000, Frederiksberg, Denmark. , (Denmark)
  • 2 Department of Clinical Biochemistry, Herlev and Gentofte Hospital, Copenhagen University Hospital, Copenhagen, Denmark. , (Denmark)
  • 3 The Copenhagen General Population Study, Herlev and Gentofte Hospital, Copenhagen University Hospital, Copenhagen, Denmark. , (Denmark)
  • 4 Department of Epidemiology Research, Statens Serum Institut, Copenhagen, Denmark. , (Denmark)
  • 5 Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark. , (Denmark)
  • 6 Center for Clinical Research and Prevention, Bispebjerg and Frederiksberg Hospital, The Capital Region, Nordre Fasanvej 57, 2000, Frederiksberg, Denmark. [email protected] , (Denmark)
  • 7 Novo Nordisk Foundation Center for Basic Metabolic Research, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark. [email protected] , (Denmark)
Type
Published Article
Journal
European Journal of Epidemiology
Publisher
Springer-Verlag
Publication Date
Apr 19, 2020
Identifiers
DOI: 10.1007/s10654-020-00630-7
PMID: 32307655
Source
Medline
Keywords
Language
English
License
Unknown

Abstract

Body mass index (BMI) has been related to risk of infections. The aim of this study was to assess the shape of the association between BMI and risk of infections and to evaluate whether such associations represent causality. We included 101,447 individuals from The Copenhagen General Population Study who had BMI measured. Outcome was hospital contacts related to infections. The shape of the association between BMI and risk of infections was examined using restricted cubic spline Cox regression. To evaluate causality, we used Mendelian randomization, an epidemiological method that counteracts confounding and reverse causality by using genetic variation as instrumental variables. We created a genetic risk score based on five genetic variants causing lifelong higher BMI and used this score in instrumental variable analysis. During median follow-up of 8.8 years, 10,263 hospital contacts related to infections were recorded. We found a U-shaped association between BMI and risk of any infection and pneumonia, and a linear association between BMI and risk of skin infection, urinary tract infection, and sepsis. In instrumental variable analyses, higher BMI was associated with increased risk of skin infection: odds ratio 1.12 (95% CI 1.03-1.22) for a genetically induced 1 unit increase in BMI. Observationally, low as well as high BMI was associated with increased risk of any infection and pneumonia, whereas only high BMI was associated with increased risk of skin infection, urinary tract infection, and sepsis. High BMI was causally associated with increased risk of skin infection.

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