When treating an elderly arthritis sufferer, you should not expect him to measure his quality of life by how much it has improved on a scale of health and well being. He wants to climb stairs without pain, and your goal is to help him do that.
…He may also ask you about other risks to his health-his own risks, not those of his community, as seen through incidence studies. It is your job to give him a satisfactory answer. And, …by the way, you are paid for it!