Down syndrome (DS) is the most common genetic cause of mental retardation. However, the biological determinants of this are poorly understood. The serum sodium/myo-inositol cotransporter gene is located on chromosome 21, and myo-inositol affects neuronal survival and function. Nevertheless, few in vivo studies have examined the role of myo-inositol in DS.
To determine if people with DS have significant differences in brain myo-inositol concentration from controls and if, within people with DS, this is related to cognitive ability.
A case-control study.
The sample was composed of 38 adults with DS without dementia (age range, 18-66 years) and 42 healthy controls (age range, 19-66 years). The DS and control groups did not differ significantly in age, sex, ethnic origin, apolipoprotein E status, or handedness.
Main Outcome Measures
Hippocampal myo-inositol concentration and cognitive performance, as measured by the Cambridge Cognitive Examination.
Hippocampal myo-inositol concentration was significantly higher in people with DS than in controls (P = .006), and within people with DS, increased myo-inositol concentration was significantly negatively correlated with overall cognitive ability (P = .04).
Adults with DS have a significantly increased brain concentration of myo-inositol, and this is associated with reduced cognitive ability. Future studies are required to relate myo-inositol concentration in people with DS to brain development and increased risk for developing Alzheimer disease.