BMI shows linear correlation with biologic markers of health
MedWire News: Higher body mass index (BMI) is clearly and strongly associated with worsening health status, research shows.
The findings are relevant to the ongoing debate about the U-shaped relationship between BMI and mortality risk, which some argue is a result of confounding by pre-existing disease.
"Much recent evidence has found that overweight adults experienced lower overall mortality than those who are underweight, normal-weight, or obese," explain Anna Zajacova (University of Wyoming, Laramie, USA) and colleagues writing in the American Journal of Epidemiology.
"These highly publicized findings imply that overweight may be the optimal weight category for overall health via its association with longevity - a conclusion with important public health implications."
To investigate, the team obtained information on 9255 participants of the 2005-6 and 2007-8 National Health and Nutrition Examination Surveys, which are representative of the noninstitutionalized civilian US population.
They then analyzed associations between BMI and levels of high-sensitivity C-reactive protein (CRP), glycated hemoglobin (HbA1c), and high-density lipoprotein cholesterol, which are markers of inflammation, metabolic risk, and cardiovascular risk, respectively.
Each of the three markers showed a "clear, strong, monotonic relation" with body weight from the lowest BMIs to the highest BMIs, such that higher weight was associated with a worse risk profile across the full adult life span.
These associations were unchanged after adjustment for age and were consistent across subgroups divided by gender and smoking status.
Discussing their results, the researchers note that using BMI as a proxy for adiposity is an important limitation of the study, since BMI cannot distinguish between lean and fat tissue or among types of adipose tissue.
Additionally, while biomarkers are predictive of chronic diseases that may lead to death, the links among the three factors are confounded by genetic predisposition toward specific conditions, medical interventions, comorbid conditions, and other effects.
"The complex associations may lead to a differently shaped population-level association between BMI and biomarkers as compared with BMI and all-cause mortality," they write.
"More research is needed to reconcile the contradictory findings of BMI's U-shaped relation with mortality versus its monotonic relation with biomarkers."
MedWire (www.medwire-news.md) is an independent clinical news service provided by Current Medicine Group, a trading division of Springer Healthcare Limited. © Springer Healthcare Ltd; 2011
By Joanna Lyford