Q. A 42 year-old man with Down syndrome presents to the neurology clinic with his parents. They are concerned about his forgetfulness. He has gained approximately 30 pounds in the past year and they notice that he snores excessively, now. But otherwise, nothing has really changed with him. They are familiar with the risks of Alzheimer's disease in Down syndrome but they do not think that is the cause. If it is not Alzheimer's disease what would be another important, common potential cause of his forgetfulness that is common in Down syndrome?