Answer:
The answer is Alzheimer's disease.
Explanation:
This condition commonly occurs at old age, and its symtpoms might progress slowly over time. In the example, Boris is suffering from later stage symptoms, which include severe memory loss, difficulty on performing tasks such as eating or moving around, and gradual loss of speech.
In the early stages of the disease, the memory loss is usually short-term (inability to recall recent conversations or events).
