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07-09-2011 | General practice | Article

Excess BMI–years predict incident diabetes


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MedWire News: The extent to which an individual's body mass index (BMI) exceeds reference levels, and the length of time for which it has done so, are linked to the risk for incident diabetes, research shows.

Higher levels of the composite measure, termed "excess BMI-years," were associated with an increased risk for diabetes that was higher for younger adults than for older individuals.

As reported in the Archives of Pediatrics and Adolescent Medicine, Joyce Lee (University of Michigan, Ann Arbor, USA) and colleagues analyzed data from the National Longitudinal Survey of Youth 1979, in which 8157 young adults, aged 14-21 years, provided measures of height, weight, and diabetes status from 1981 through to 2006.

The authors evaluated the relationship between the degree and duration of excess BMI and incident diabetes through analysis of a term analogous to smoking pack-years, which they called "excess BMI-years." This is a composite measure of the degree to which an individual's BMI exceeds his or her reference BMI and the duration for which he or she carries excess BMI.

"No studies have attempted to characterize such a term and its relation with incident diabetes, to our knowledge," say the authors.

"Understanding this relation is important for increasing the reliability of US diabetes projections and to better understand the consequences of increasing weight among younger US generations," they add.

The team found that, for the overall population, mean excess BMI-years increased with age, at -10.2, -7.7, 1.1, and 11.9 at ages 25, 30, 35, and 40 years, respectively.

They also found that higher excess BMI-years were associated with a greater risk for self-reported incident diabetes.

For example, a White man aged 40 years with 200 cumulative excess BMI-years was 2.94 times more likely to develop diabetes compared with a man of the same age and race with 100 excess BMI-years.

They used logistic regression modeling to show the predicted incidence of diabetes at a specific age as a function of excess BMI-years, given that diabetes had not occurred at an earlier age.

This showed that at an excess BMI-years value of 200, the predicted incidence of developing diabetes was higher for younger-onset (age 30 years) compared with older-onset (ages 35 and 40 years) diabetes.

"This information is critical for increasing the reliability of predictions of diabetes rates and diabetes burden and for achieving a better understanding of the consequences of increasing weight among younger generations in the United States," say Lee and team.

They suggest that weight interventions for diabetes prevention may be more effective at younger compared with older ages and that public health programs may need to prioritize accordingly.

By Sally Robertson

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