Abnormal or unpleasant odors may be caused by diseased or necrotic tissue in the respiratory or upper gastrointestinal tracts, including mouth and nasal cavity. Diseased teeth are a common cause in dogs and cats. In addition, certain metabolic diseases may produce distinctive breath odor, e.g. ketoacidosis, uremia.
Practically elderly is a person who needs special consideration due to advanced age. Which can happen in late 50s or in late 80s. If he or she can punch your lights out for calling them elderly, and you cannot run from them either, they possibly aren't.
60 to 70 is on the young side of being elderly. 70 to 80 is the middle of being elderly. 80 to 90 is definitely elderly. That is if you judge by age. Look in the obituaries and you will see many never reach the age of 60. I know people in their 80's that are in better health than those in their 60's.