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Why do thin people have elevated all-cause mortality? Evidence on confounding and reverse causality in the association of adiposity and COPD from the British Women's Heart and Health Study.

Dale C, Nüesch E, Prieto-Merino D, Choi M, Amuzu A, Ebrahim S, Casas JP, Davey-Smith G - PLoS ONE (2015)

Bottom Line: However, this could arise from confounding or reverse causality.Low BMI was found to be associated with increased COPD risk while low WHR was not (OR = 2.2; 95% CI 1.3-3.1 versus OR = 1.2; 95% CI 0.7-1.6).Potential confounding variables (e.g. smoking) and markers of ill-health (e.g. unintentional weight loss) were found to be higher in low BMI but not in low WHR.

View Article: PubMed Central - PubMed

Affiliation: Department of Non-communicable Disease Epidemiology, Faculty of Epidemiology and Population Health, London School of Hygiene & Tropical Medicine, London, United Kingdom.

ABSTRACT
Low adiposity has been linked to elevated mortality from several causes including respiratory disease. However, this could arise from confounding or reverse causality. We explore the association between two measures of adiposity (BMI and WHR) with COPD in the British Women's Heart and Health Study including a detailed assessment of the potential for confounding and reverse causality for each adiposity measure. Low BMI was found to be associated with increased COPD risk while low WHR was not (OR = 2.2; 95% CI 1.3-3.1 versus OR = 1.2; 95% CI 0.7-1.6). Potential confounding variables (e.g. smoking) and markers of ill-health (e.g. unintentional weight loss) were found to be higher in low BMI but not in low WHR. Women with low BMI have a detrimental profile across a broad range of health markers compared to women with low WHR, and women with low WHR do not appear to have an elevated COPD risk, lending support to the hypothesis that WHR is a less confounded measure of adiposity than BMI. Low adiposity does not in itself appear to increase the risk of respiratory disease, and the apparent adverse consequences of low BMI may be due to reverse causation and confounding.

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Gradual adjustment of associations between COPD and adiposity by age, lifestyle and ill-health.
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pone.0115446.g003: Gradual adjustment of associations between COPD and adiposity by age, lifestyle and ill-health.

Mentions: The effect of the incremental adjustment on COPD diagnosis by BMI category relative to baseline 22<BMI<24 is illustrated in Fig 3 (S8 Table). The odds of COPD in the lowest BMI category remained higher (OR = 2.2; 95% CI 1.3–3.1) compared to normal BMI even after full adjustment for age, lifestyle and ill-health, although the point estimates did move closer to one on adjustment. There was no evidence for elevated odds of COPD for any category of higher BMI. Unlike BMI, there is no evidence for increased odds of COPD in the lowest WHR category relative to the baseline 0.72<WHR<0.77 (OR = 1.2; 95% CI 0.7–1.6), but we found increasing odds of COPD in the higher WHR categories.


Why do thin people have elevated all-cause mortality? Evidence on confounding and reverse causality in the association of adiposity and COPD from the British Women's Heart and Health Study.

Dale C, Nüesch E, Prieto-Merino D, Choi M, Amuzu A, Ebrahim S, Casas JP, Davey-Smith G - PLoS ONE (2015)

Gradual adjustment of associations between COPD and adiposity by age, lifestyle and ill-health.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4401726&req=5

pone.0115446.g003: Gradual adjustment of associations between COPD and adiposity by age, lifestyle and ill-health.
Mentions: The effect of the incremental adjustment on COPD diagnosis by BMI category relative to baseline 22<BMI<24 is illustrated in Fig 3 (S8 Table). The odds of COPD in the lowest BMI category remained higher (OR = 2.2; 95% CI 1.3–3.1) compared to normal BMI even after full adjustment for age, lifestyle and ill-health, although the point estimates did move closer to one on adjustment. There was no evidence for elevated odds of COPD for any category of higher BMI. Unlike BMI, there is no evidence for increased odds of COPD in the lowest WHR category relative to the baseline 0.72<WHR<0.77 (OR = 1.2; 95% CI 0.7–1.6), but we found increasing odds of COPD in the higher WHR categories.

Bottom Line: However, this could arise from confounding or reverse causality.Low BMI was found to be associated with increased COPD risk while low WHR was not (OR = 2.2; 95% CI 1.3-3.1 versus OR = 1.2; 95% CI 0.7-1.6).Potential confounding variables (e.g. smoking) and markers of ill-health (e.g. unintentional weight loss) were found to be higher in low BMI but not in low WHR.

View Article: PubMed Central - PubMed

Affiliation: Department of Non-communicable Disease Epidemiology, Faculty of Epidemiology and Population Health, London School of Hygiene & Tropical Medicine, London, United Kingdom.

ABSTRACT
Low adiposity has been linked to elevated mortality from several causes including respiratory disease. However, this could arise from confounding or reverse causality. We explore the association between two measures of adiposity (BMI and WHR) with COPD in the British Women's Heart and Health Study including a detailed assessment of the potential for confounding and reverse causality for each adiposity measure. Low BMI was found to be associated with increased COPD risk while low WHR was not (OR = 2.2; 95% CI 1.3-3.1 versus OR = 1.2; 95% CI 0.7-1.6). Potential confounding variables (e.g. smoking) and markers of ill-health (e.g. unintentional weight loss) were found to be higher in low BMI but not in low WHR. Women with low BMI have a detrimental profile across a broad range of health markers compared to women with low WHR, and women with low WHR do not appear to have an elevated COPD risk, lending support to the hypothesis that WHR is a less confounded measure of adiposity than BMI. Low adiposity does not in itself appear to increase the risk of respiratory disease, and the apparent adverse consequences of low BMI may be due to reverse causation and confounding.

Show MeSH
Related in: MedlinePlus