Britain seems like such a weird and scary country, where everything is a thought crime.
Kieran stated a medical fact.
People sleep less as they age. Eileen has an extreme aversion to the aging process, as evidenced by the mutilation she's done to her face and her desperate attempts to present herself as youthful. Kieran played along with her delusion, which is what people have to do when confronted with the faith-based and anti-science religion of Progressivism.