The effect of elevated body mass index on ischemic heart disease risk: causal estimates from a Mendelian randomisation approach.

<h4>Background</h4>Adiposity, assessed as elevated body mass index (BMI), is associated with increased risk of ischemic heart disease (IHD); however, whether this is causal is unknown. We tested the hypothesis that positive observational associations between BMI and IHD are causal.<h4...

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Autores principales: Børge G Nordestgaard, Tom M Palmer, Marianne Benn, Jeppe Zacho, Anne Tybjaerg-Hansen, George Davey Smith, Nicholas J Timpson
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Publicado: Public Library of Science (PLoS) 2012
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spelling oai:doaj.org-article:979c92f2ac1d4f96a089edcea3a8a9622021-11-18T05:42:17ZThe effect of elevated body mass index on ischemic heart disease risk: causal estimates from a Mendelian randomisation approach.1549-12771549-167610.1371/journal.pmed.1001212https://doaj.org/article/979c92f2ac1d4f96a089edcea3a8a9622012-01-01T00:00:00Zhttps://www.ncbi.nlm.nih.gov/pmc/articles/pmid/22563304/?tool=EBIhttps://doaj.org/toc/1549-1277https://doaj.org/toc/1549-1676<h4>Background</h4>Adiposity, assessed as elevated body mass index (BMI), is associated with increased risk of ischemic heart disease (IHD); however, whether this is causal is unknown. We tested the hypothesis that positive observational associations between BMI and IHD are causal.<h4>Methods and findings</h4>In 75,627 individuals taken from two population-based and one case-control study in Copenhagen, we measured BMI, ascertained 11,056 IHD events, and genotyped FTO(rs9939609), MC4R(rs17782313), and TMEM18(rs6548238). Using genotypes as a combined allele score in instrumental variable analyses, the causal odds ratio (OR) between BMI and IHD was estimated and compared with observational estimates. The allele score-BMI and the allele score-IHD associations used to estimate the causal OR were also calculated individually. In observational analyses the OR for IHD was 1.26 (95% CI 1.19-1.34) for every 4 kg/m(2) increase in BMI. A one-unit allele score increase associated with a 0.28 kg/m(2) (95 CI% 0.20-0.36) increase in BMI and an OR for IHD of 1.03 (95% CI 1.01-1.05) (corresponding to an average 1.68 kg/m(2) BMI increase and 18% increase in the odds of IHD for those carrying all six BMI increasing alleles). In instrumental variable analysis using the same allele score the causal IHD OR for a 4 kg/m(2) increase in BMI was 1.52 (95% CI 1.12-2.05).<h4>Conclusions</h4>For every 4 kg/m(2) increase in BMI, observational estimates suggested a 26% increase in odds for IHD while causal estimates suggested a 52% increase. These data add evidence to support a causal link between increased BMI and IHD risk, though the mechanism may ultimately be through intermediate factors like hypertension, dyslipidemia, and type 2 diabetes. This work has important policy implications for public health, given the continuous nature of the BMI-IHD association and the modifiable nature of BMI. This analysis demonstrates the value of observational studies and their ability to provide unbiased results through inclusion of genetic data avoiding confounding, reverse causation, and bias.Børge G NordestgaardTom M PalmerMarianne BennJeppe ZachoAnne Tybjaerg-HansenGeorge Davey SmithNicholas J TimpsonPublic Library of Science (PLoS)articleMedicineRENPLoS Medicine, Vol 9, Iss 5, p e1001212 (2012)
institution DOAJ
collection DOAJ
language EN
topic Medicine
R
spellingShingle Medicine
R
Børge G Nordestgaard
Tom M Palmer
Marianne Benn
Jeppe Zacho
Anne Tybjaerg-Hansen
George Davey Smith
Nicholas J Timpson
The effect of elevated body mass index on ischemic heart disease risk: causal estimates from a Mendelian randomisation approach.
description <h4>Background</h4>Adiposity, assessed as elevated body mass index (BMI), is associated with increased risk of ischemic heart disease (IHD); however, whether this is causal is unknown. We tested the hypothesis that positive observational associations between BMI and IHD are causal.<h4>Methods and findings</h4>In 75,627 individuals taken from two population-based and one case-control study in Copenhagen, we measured BMI, ascertained 11,056 IHD events, and genotyped FTO(rs9939609), MC4R(rs17782313), and TMEM18(rs6548238). Using genotypes as a combined allele score in instrumental variable analyses, the causal odds ratio (OR) between BMI and IHD was estimated and compared with observational estimates. The allele score-BMI and the allele score-IHD associations used to estimate the causal OR were also calculated individually. In observational analyses the OR for IHD was 1.26 (95% CI 1.19-1.34) for every 4 kg/m(2) increase in BMI. A one-unit allele score increase associated with a 0.28 kg/m(2) (95 CI% 0.20-0.36) increase in BMI and an OR for IHD of 1.03 (95% CI 1.01-1.05) (corresponding to an average 1.68 kg/m(2) BMI increase and 18% increase in the odds of IHD for those carrying all six BMI increasing alleles). In instrumental variable analysis using the same allele score the causal IHD OR for a 4 kg/m(2) increase in BMI was 1.52 (95% CI 1.12-2.05).<h4>Conclusions</h4>For every 4 kg/m(2) increase in BMI, observational estimates suggested a 26% increase in odds for IHD while causal estimates suggested a 52% increase. These data add evidence to support a causal link between increased BMI and IHD risk, though the mechanism may ultimately be through intermediate factors like hypertension, dyslipidemia, and type 2 diabetes. This work has important policy implications for public health, given the continuous nature of the BMI-IHD association and the modifiable nature of BMI. This analysis demonstrates the value of observational studies and their ability to provide unbiased results through inclusion of genetic data avoiding confounding, reverse causation, and bias.
format article
author Børge G Nordestgaard
Tom M Palmer
Marianne Benn
Jeppe Zacho
Anne Tybjaerg-Hansen
George Davey Smith
Nicholas J Timpson
author_facet Børge G Nordestgaard
Tom M Palmer
Marianne Benn
Jeppe Zacho
Anne Tybjaerg-Hansen
George Davey Smith
Nicholas J Timpson
author_sort Børge G Nordestgaard
title The effect of elevated body mass index on ischemic heart disease risk: causal estimates from a Mendelian randomisation approach.
title_short The effect of elevated body mass index on ischemic heart disease risk: causal estimates from a Mendelian randomisation approach.
title_full The effect of elevated body mass index on ischemic heart disease risk: causal estimates from a Mendelian randomisation approach.
title_fullStr The effect of elevated body mass index on ischemic heart disease risk: causal estimates from a Mendelian randomisation approach.
title_full_unstemmed The effect of elevated body mass index on ischemic heart disease risk: causal estimates from a Mendelian randomisation approach.
title_sort effect of elevated body mass index on ischemic heart disease risk: causal estimates from a mendelian randomisation approach.
publisher Public Library of Science (PLoS)
publishDate 2012
url https://doaj.org/article/979c92f2ac1d4f96a089edcea3a8a962
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