Second childhood and Senile dementia

Second childhood noun - The state or period of mental decline that typically accompanies old age.

Senile dementia and second childhood are semantically related. In some cases you can use "Senile dementia" instead a noun phrase "Second childhood".

Senile dementia noun - Dementia of the aged; results from degeneration of the brain in the absence of cerebrovascular disease.

Second childhood and senile dementia are semantically related. You can use "Second childhood" instead a noun phrase "Senile dementia".