Skip to main content

Thank you for visiting You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

Issues related to modeling the body mass index–mortality association: the shape of the association and the effects of smoking status


Research on the relationship between body mass index (BMI) and mortality has led to conflicting results; a lack of agreement about how to adjust for confounders, such as smoking status, has added to the problem. Complicating such analyses is the fact that the BMI–mortality association is not a symmetric quadratic relationship; the distribution tends to be skewed to the right, causing the optimal BMI—where mortality is at a minimum—to be overestimated. One way to overcome this problem is by transformation of the BMI distribution to normality. The authors suggest several approaches for doing so, including the use of 1/BMI, or lean body mass index, instead of BMI in modeling. Data sets on 50 cohorts from approximately 30 international studies were used to examine the association (direct, inverse, quadratic or none) between BMI and mortality and to investigate the possible interaction of smoking status. Of the 50 cohorts, 36 showed a quadratic association between BMI and mortality, 10 showed no association and 1 showed a direct association between lean BMI and mortality. Only three cohorts showed a significant interaction between BMI and smoking, which was approximately what one would expect from a 5% significance test, even if no interaction existed. The association between BMI and mortality is not changed when smoking status is ignored in a model or when data on smokers are excluded from analysis. The methodology used in this study could be extended to look for other interactions.

This is a preview of subscription content

Access options

Buy article

Get time limited or full article access on ReadCube.


All prices are NET prices.

Figure 1
Figure 2


  1. McGee DL, Diverse Populations Collaboration. Body mass index and mortality: a meta-analysis based on person-level data from twenty-six observational studies. Ann Epidemiol 2005; 15: 87–97.

    Article  Google Scholar 

  2. Durazo-Arvizu R, McGee D, Li Z, Cooper R . Establishing the nadir of the body mass index–mortality relationship: a case study. J Am Stat Assoc 1997; 92: 1312–1319.

    Article  Google Scholar 

  3. Waaler HT . Height, weight and mortality. The Norwegian experience. Acta Med Scand Suppl 1984; 679: 1–56.

    CAS  PubMed  Google Scholar 

  4. Goetghebeur E, Pocock SJ . Detection and estimation of J-shaped risk–response relationships. J R Stat Soc Ser A Stat Soc 1995; 158: 107–121.

    Article  Google Scholar 

  5. Allison DB, Faith MS . On estimating the minima of BMI–mortality curves. Int J Obes Relat Metab Disord 1996; 20: 496–498.

    CAS  PubMed  Google Scholar 

  6. Cornfield J, Gordon T, Smith WW . Quantal response curves for experimentally uncontrolled variables. Bull Int Stat Inst 1961; 38: 97–115.

    Google Scholar 

  7. Kay R, Little S . Transformations of the explanatory variables in the logistic regression model for binary data. Biometrika 1987; 74: 495–501.

    Article  Google Scholar 

  8. Nevill AM, Holder RL . Body mass index: a measure of fatness or leanness? Br J Nutr 1995; 73: 507–516.

    CAS  Article  Google Scholar 

  9. BMI in Diverse Populations Collaborative Group. Effect of smoking on the body mass index–mortality relation: empirical evidence from 15 studies. Am J Epidemiol 1999; 150: 1297–1308.

    Article  Google Scholar 

Download references

Author information

Authors and Affiliations


Corresponding author

Correspondence to R A Durazo-Arvizu.

Rights and permissions

Reprints and Permissions

About this article

Cite this article

Durazo-Arvizu, R., Cooper, R. Issues related to modeling the body mass index–mortality association: the shape of the association and the effects of smoking status. Int J Obes 32, S52–S55 (2008).

Download citation

  • Published:

  • Issue Date:

  • DOI:


  • BMI
  • all-cause mortality
  • model
  • smoking
  • confounders
  • data exclusion

Further reading


Quick links