What is wrong about this sentence is that dementia is implied to be a physical problem ("dementia and other physical weaknesses").
While old age can come with many physical difficulties for individuals, the disorders gathered under the broad term "dementia" do not typically affect a person's appearance or motor functions. The areas affected have to do with cognitive abilities (thinking, problem-solving, etc.). These include memory (like Alzheimer's), feelings, language, and repetitive tasks like cooking.
