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07-15-2021 | Epidemiology | News

Global variation in optimal BMI, age cutoffs for diabetes screening

Eleanor McDermid

medwireNews: Researchers find large geographic differences in the influence of BMI and age on the risk for type 2 diabetes in low- and middle-income countries (LMICs).

“Although lower BMI cutoffs for the detection of metabolic risk have been recommended for Asian populations compared with all other populations globally, which is consistent with our findings, we found similar results in other geographical regions, such as the Middle East and north Africa,” the team writes in The Lancet.

The optimal BMI threshold for predicting diabetes was a relatively low 23.9 kg/m2 for women and 23.8 kg/m2 for men in LMICs in east, south, and southeast Asia, and 24.2 kg/m2 for men in the Middle East and north Africa.

Also, the optimal BMI cutoff was virtually identical for women and men in east, south, and southeast Asia, whereas in most other regions it was higher in women than men.

At the other end of the scale, BMI cutoffs were 28.0 kg/m2 for women in Europe and central Asia, 28.1 kg/m2 for men in Oceania, and 28.3 kg/m2 for women in the Middle East and north Africa, and in Latin America and the Caribbean.

These cutoffs were derived from the results of 58 nationally representative surveys in LMICs, which provided data of 685,616 people aged an average of 42.6 years. A total of 9.3% of these people had diabetes, 27.2% were overweight, and 21.0% were obese.

Jennifer Manne-Goehler (Massachusetts General Hospital, Boston, USA) and study co-authors also found that the increase in risk across BMI categories was markedly steeper in some areas than others.

For example, the risk ratios for diabetes in men in sub-Saharan Africa rose from 1.43 for the upper-normal BMI category (23 to <25 kg/m2) to 3.46 for the obese category (>30 kg/m2), compared with the normal BMI category (18.5 to <23 kg/m2). The corresponding risk ratios for men in Oceania were 1.12 and 1.56.

And although age had the expected effect of increasing diabetes risk, the team found “steeply” increased risk in the 25–34 years’ age group among men in sub-Saharan Africa, and in the 35–44 years’ group in all regions.

Manne-Goehler and colleagues say their results imply that, in many LMICs, screening for diabetes should begin at a younger age and lower BMI than the 40 years and 25 kg/m2 currently advised by the World Health Organization.

They also caution that “BMI performed modestly overall” as an indicator of diabetes risk.

“Given this finding, other low-cost anthropometric measures, such as waist circumference, might be explored to further optimise assessment of metabolic risk in these settings,” they suggest.

In a linked commentary, Siméon Pierre Choukem (University of Dschang, Cameroon) and Christian Akem Dimala (Reading Hospital, Pennsylvania, USA) write: “These results have major public health implications, as the actual burden of diabetes in LMICs is probably underestimated because of current screening guidelines, and to what extent is unclear.

“In fact, the current trends in obesity and diabetes in LMICs closely mirror worsening global trends, and they appear even more perturbing in the younger age groups in LMICs than in [high-income countries].”

medwireNews is an independent medical news service provided by Springer Healthcare Ltd. © 2021 Springer Healthcare Ltd, part of the Springer Nature Group

Lancet 2021; 398: 238–248
Lancet 2021; 398: 190–192

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