A preliminary examination of brain morphometry in youth with Down syndrome with and without parent-reported sleep difficulties.

The study included only 17 participants with Down syndrome and sleep difficulties and 9 with Down syndrome without sleep difficulties, so it is preliminary and small. Sleep difficulty was defined by one parent question about awakening, restlessness, or snoring, not by objective sleep testing, and the severity of sleep problems was not measured. The design was cross-sectional and retrospective, so it cannot show that sleep difficulties caused smaller brain volumes. The sleep-difficulty group included participants with and without parent-reported sleep apnea, so the findings do not show that sleep apnea alone was involved. Many brain regions were compared, and after total brain volume was controlled, several smaller-volume findings did not remain significant. The sleep-difficulty group had more congenital heart defects, and although the authors ran checks, this comorbidity cannot be fully ruled out as a contributor. Participants ranged from 5 to 25 years old, and the study assumed a similar age-brain volume relationship across groups. The study did not include a typically developing comparison group with sleep difficulties, did not measure brainstem substructures such as the pons, and did not examine effects of sleep treatment.

Do not conclude that poor sleep causes smaller brain volume in Down syndrome. The study compared groups at one time point, used a single parent report question to define sleep difficulty, and cannot separate sleep effects from total brain size or other medical conditions.