Who is considered elderly or old age?

No strict definition. Clinically. Some studies used to have an age limit, but it was considered discriminatory. Some people are old at 40 others remain young at 80...As the song goes, young at heart. The consideration should be more "hale" or "frail" when medical decisions are involved. A lot depends on how many illnesses, medications, and organs no longer function well. Elderly sounds polite; old seems inconsiderate.