Final answer:
Genetic factors, including the presence of an extra chromosome in Down syndrome and shared susceptibility genes, may explain the increased risk of Alzheimer's disease in women who give birth to a child with Down syndrome before the age of 35. The genetic connection is strengthened by similarities in brain pathology, like the formation of plaques, and cognitive symptoms between the two conditions.
Step-by-step explanation:
The observation that women who give birth to a child with Down syndrome before age 35 are at increased risk of developing Alzheimer's disease suggests a genetic connection between the two conditions. Down syndrome is caused by the addition of an extra chromosome 21 (47,XY +21), which can increase the production of amyloid precursor protein (APP), a protein associated with the plaques found in Alzheimer's disease. Moreover, the increased risk of having a child with Down syndrome with maternal age is due to the higher likelihood of chromosomal abnormalities in the eggs of older women.
Genetic factors like the presence of the Apolipoprotein E (APOE) gene variant E4 can contribute to a person's likelihood of developing Alzheimer's disease. It's also noteworthy that Alzheimer's and Down syndrome share characteristics such as the formation of characteristic brain plaques and cognitive decline. Therefore, the genetic overlap, such as shared pathways or susceptibility genes, could potentially explain why giving birth to a child with Down syndrome may be associated with a higher Alzheimer's risk in younger mothers. However, studies are ongoing to fully understand the connection between Down syndrome and Alzheimer's disease.