Decreased resting metabolic rate among persons with Down Syndrome.

Objective: To compare the resting metabolic rates (RMRs) of adults with and without DS while controlling for potential confounds.
Design: Observational, cross-sectional study.
Setting: Outpatient core of the New York Obesity Research Center.
Subjects: Thirteen adults (nine males and four females) with DS were compared to 77 adults without DS.
Measurements: RMR was measured by indirect calorimetry. Fat mass (FM) and fat free mass (FFM) were determined using dual energy X-ray absorptiometry (DXA). Thyroid function (thyroxin, T3 uptake, and free T4) were determined from fasting blood samples for all DS subjects and a subset of the controls.
Results: An analysis of covariance was conducted in which DS status was the independent variable. Covariates were sex, FFM, FM, age, and T4. After controlling for sex, FFM, FM, age, and height, persons with DS had lower RMRs than persons without DS (F(1,83) = 7.697, P = 0.007; eta = 0.29). In terms of kcalories, the adjusted means were 1333.5 for DS subjects and 1670.1 for non-DS subjects, a difference of 20.8% relative to the grand mean. When thyroxine was added to the regression the effect of DS on RMR was of questionable significance.
Conclusion: This research demonstrates that persons with DS have lower RMRs than do persons without DS. This difference persists after controlling for obvious confounds and was of a moderate magnitude.