Relationship between body mass index and fracture risk is mediated by bone mineral density

Chan, MY; Frost, SA; Center, JR; Eisman, JA; Nguyen, TV

Relationship between body mass index and fracture risk is mediated by bone mineral density

Chan, MY Frost, SA Center, JR Eisman, JA Nguyen, TV

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Publication Type:: Journal Article
Citation:: Journal of Bone and Mineral Research, 2014, 29 (11), pp. 2327 - 2335
Issue Date:: 2014-11-01

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Field	Value	Language
dc.contributor.author	Chan, MY	en_US
dc.contributor.author	Frost, SA	en_US
dc.contributor.author	Center, JR	en_US
dc.contributor.author	Eisman, JA	en_US
dc.contributor.author	Nguyen, TV https://orcid.org/0000-0002-3246-6281	en_US
dc.date.available	2014-05-20	en_US
dc.date.issued	2014-11-01	en_US
dc.identifier.citation	Journal of Bone and Mineral Research, 2014, 29 (11), pp. 2327 - 2335	en_US
dc.identifier.issn	0884-0431	en_US
dc.identifier.uri	http://hdl.handle.net/10453/107362
dc.description.abstract	© 2014 American Society for Bone and Mineral Research. The relationship between body mass index (BMI) and fracture risk is controversial. We sought to investigate the effect of collinearity between BMI and bone mineral density (BMD) on fracture risk, and to estimate the direct and indirect effect of BMI on fracture with BMD being the mediator. The study involved 2199 women and 1351 men aged 60 years or older. BMI was derived from baseline weight and height. Femoral neck BMD was measured by dual-energy X-ray absorptiometry (DXA; GE-LUNAR, Madison, WI, USA). The incidence of fragility fracture was ascertained by X-ray reports from 1991 through 2012. Causal mediation analysis was used to assess the mediated effect of BMD on the BMI-fracture relationship. Overall, 774 women (35% of total women) and 258 men (19%) had sustained a fracture. Approximately 21% of women and 20% of men were considered obese (BMI ≥ 30). In univariate analysis, greater BMI was associated with reduced fracture risk in women (hazard ratio [HR] 0.92; 95% confidence interval [CI], 0.85 to 0.99) and in men (HR 0.77; 95% CI, 0.67 to 0.88). After adjusting for femoral neck BMD, higher BMI was associated with greater risk of fracture in women (HR 1.21; 95% CI, 1.11 to 1.31) but not in men (HR 0.96; 95% CI, 0.83 to 1.11). Collinearity had minimal impact on the BMD-adjusted results (variance inflation factor [VIF]=1.2 for men and women). However, in mediation analysis, it was found that the majority of BMI effect on fracture risk was mediated by femoral neck BMD. The overall mediated effect estimates were -0.048 (95% CI, -0.059 to -0.036; p<0.001) in women and -0.030 (95% CI, -0.042 to -0.018; p<0.001) in men. These analyses suggest that there is no significant direct effect of BMI on fracture, and that the observed association between BMI and fracture risk is mediated by femoral neck BMD in both men and women.	en_US
dc.relation.ispartof	Journal of Bone and Mineral Research	en_US
dc.relation.isbasedon	10.1002/jbmr.2288	en_US
dc.subject.classification	Anatomy & Morphology	en_US
dc.subject.mesh	Humans	en_US
dc.subject.mesh	Femoral Neck Fractures	en_US
dc.subject.mesh	Body Mass Index	en_US
dc.subject.mesh	Risk Factors	en_US
dc.subject.mesh	Prospective Studies	en_US
dc.subject.mesh	Sex Factors	en_US
dc.subject.mesh	Bone Density	en_US
dc.subject.mesh	Aged	en_US
dc.subject.mesh	Aged, 80 and over	en_US
dc.subject.mesh	Middle Aged	en_US
dc.subject.mesh	Female	en_US
dc.subject.mesh	Male	en_US
dc.subject.mesh	Radiography	en_US
dc.title	Relationship between body mass index and fracture risk is mediated by bone mineral density	en_US
dc.type	Journal Article
utslib.citation.volume	11	en_US
utslib.citation.volume	29	en_US
utslib.for	0903 Biomedical Engineering	en_US
utslib.for	06 Biological Sciences	en_US
utslib.for	09 Engineering	en_US
utslib.for	11 Medical and Health Sciences	en_US
pubs.embargo.period	Not known	en_US
pubs.organisational-group	/University of Technology Sydney
pubs.organisational-group	/University of Technology Sydney/Faculty of Engineering and Information Technology
pubs.organisational-group	/University of Technology Sydney/Faculty of Engineering and Information Technology/School of Biomedical Engineering
pubs.organisational-group	/University of Technology Sydney/Strength - CHT - Health Technologies
utslib.copyright.status	closed_access
pubs.issue	11	en_US
pubs.publication-status	Published	en_US
pubs.volume	29	en_US

Abstract:

© 2014 American Society for Bone and Mineral Research. The relationship between body mass index (BMI) and fracture risk is controversial. We sought to investigate the effect of collinearity between BMI and bone mineral density (BMD) on fracture risk, and to estimate the direct and indirect effect of BMI on fracture with BMD being the mediator. The study involved 2199 women and 1351 men aged 60 years or older. BMI was derived from baseline weight and height. Femoral neck BMD was measured by dual-energy X-ray absorptiometry (DXA; GE-LUNAR, Madison, WI, USA). The incidence of fragility fracture was ascertained by X-ray reports from 1991 through 2012. Causal mediation analysis was used to assess the mediated effect of BMD on the BMI-fracture relationship. Overall, 774 women (35% of total women) and 258 men (19%) had sustained a fracture. Approximately 21% of women and 20% of men were considered obese (BMI ≥ 30). In univariate analysis, greater BMI was associated with reduced fracture risk in women (hazard ratio [HR] 0.92; 95% confidence interval [CI], 0.85 to 0.99) and in men (HR 0.77; 95% CI, 0.67 to 0.88). After adjusting for femoral neck BMD, higher BMI was associated with greater risk of fracture in women (HR 1.21; 95% CI, 1.11 to 1.31) but not in men (HR 0.96; 95% CI, 0.83 to 1.11). Collinearity had minimal impact on the BMD-adjusted results (variance inflation factor [VIF]=1.2 for men and women). However, in mediation analysis, it was found that the majority of BMI effect on fracture risk was mediated by femoral neck BMD. The overall mediated effect estimates were -0.048 (95% CI, -0.059 to -0.036; p<0.001) in women and -0.030 (95% CI, -0.042 to -0.018; p<0.001) in men. These analyses suggest that there is no significant direct effect of BMI on fracture, and that the observed association between BMI and fracture risk is mediated by femoral neck BMD in both men and women.

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http://hdl.handle.net/10453/107362