Is body mass index a useful measure of excess body fatness in adolescents and young adults with Down syndrome?
Use the 95th BMI percentile—not the 85th—to spot obesity in youth with Down syndrome.
01Research in Context
What this study did
Doctors wanted to know if the same BMI cut-offs used for other teens work for teens with Down syndrome. They compared BMI scores to body-fat scans in a group of youth with Down syndrome.
The team used DXA scans as the true measure of extra fat. They checked how well the 85th and 95th BMI percentiles spotted that fat.
What they found
Only the 95th BMI percentile did a good job. It caught excess fat 91 percent of the time.
The 85th percentile flagged too many kids as obese when they were not. Using it would lead to false alarms.
How this fits with other research
Waldron et al. (2023) later showed the same 95th cut-off stays useful in adults. It links high BMI to low bone mass, so one simple number now screens for two risks.
Gastelum Guerrero et al. (2024) pooled lipid studies and found worse cholesterol in Down syndrome. Pairing the 95th BMI rule with lipid checks gives a fuller health picture.
Geurts et al. (2008) and Ellingsen et al. (2014) already proved these adults have fragile bones. The 2013 BMI rule fills the gap by giving frontline clinics an easy first alert before ordering costly DXA scans.
Why it matters
You can now use the 95th percentile BMI alone to screen for obesity in teens and young adults with Down syndrome. No extra charts or tools needed. Flag those at or above the cut-off for nutrition or exercise referrals, and remember they may also need bone and lipid checks later.
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02At a glance
03Original abstract
BACKGROUND: To determine the validity of body mass index (BMI) to identify excess fatness in youth with Down syndrome (DS). METHODS: Using the Centers for Disease Control and Prevention (CDC) growth reference, we defined overweight (≥ 85th percentile) and obesity (≥ 95th percentile) based on participants' age- and sex-specific BMI z-scores, calculated from measured height and weight. Percentage body fat was measured by dual-energy X-ray absorptiometry. We determined sensitivity, specificity, positive predictive value, negative predictive value and efficiency of BMI percentiles to identify excess adiposity relative to elevated percentage body fat cut-offs developed from the Pediatric Rosetta Body Composition project in 32 youth (20 boys/12 girls), ages 13-21 years with Down syndrome. RESULTS: For adolescents with Down syndrome using the cut-off points of 95th percentile for BMI (obesity), sensitivity and specificity were 71% and 96% respectively. Positive predictive value was 83% and negative predictive value was 92%. Overall efficiency was 91%. Sensitivity and specificity for BMI cut-offs above the 85th percentile (overweight) were 100% and 60% respectively. The positive predictive value was 41% and negative predictive value was 100%. Overall efficiency was 69%. CONCLUSION: On the whole, the obesity (≥ 95th percentile) cut-off performs better than the overweight cut-off (85th-94th percentile) in identifying elevated fatness in youth with DS.
Journal of intellectual disability research : JIDR, 2013 · doi:10.1111/j.1365-2788.2012.01605.x