Age. Mention age if it is relevant, but be aware that age-related terms (matronly, well-preserved, and so on) can carry derogatory connotations. Describing Mr. Fry as elderly but still active may sound polite to you, but chances are Mr. Fry would prefer being called an active seventy-eight-year-old—or just a seventy-eight-year-old, which eliminates the unstated assumption of surprise that he is active at his age.