People with health problems such as sickle-cell anemia and chronic lung and heart disorders should be careful. Altitude tends to put a strain on such diseases. My best advice for your husband is to get checked out before making the move to an altitude of 9000 feet.
Altitude sickness has nothing to do with fitness level, age or gender. It depends on three factors: elevation, rate of ascent and individual susceptibility. Resource: Article Altitude Sickness