DEAR DR. ROACH: I am 79 and can move around without any problem. I walk five days a week, and my weight is normal. However, it seems to me that many people -- some younger than I am -- have mobility problems. I wonder what causes this problem. Is it lack of exercise, genes, weight, etc.? -- E.G. ANSWER: Be very grateful that you can move around without a problem, as most people in their late 70s do have mobility issues. The most common reason is osteoarthritis, but there are many causes, such as neurological diseases, cardiovascular issues and other...

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