I recently moved from the Denver area, after living there for 6 years.
At 5,200 feet, the thin air is no big deal, the Broncos like to make visiting teams think it is.
My mother in law is 82 years old, two artificial knees, a bad hip, 50 pounds over weight and high blood pressure. She gets off the plane from Florida and goes about her visit with zero problems.
Back in October she helped make the food for a wedding for 100 people attending.