One major thing you have to worry about with octogenarians is falls. There are all sorts of injuries related to falls but the worst one is to break a hip. It can happen very easily.

When old folks break a hip, it sets off a chain of consequences that are really, really bad for their health and quality of life. To begin with, it immediately requires hospitalization and major surgery. Then, a period of immobilization starting with a "short term" stay in a nursing home followed by weeks of rehabilitation. During all that time, they're susceptible to many different complications. It's basically the beginning of the end for many.

This happened to my mother. In the course of 3 years: broken hip, stroke, and UTI followed by near-fatal sepsis (which precipitated dementia). After all that she lost the ability to walk and we had to put her in a skilled nursing facility for the rest of her life.

Best thing you can do is to make sure you get advice from an elder-care attorney about end-of-life problems and financial planning. There can be dire financial consequences for the family if any money is transferred from the elderly to family members within 5 years of going on medical assistance (thanks to George W Bush's "deficit reduction act" of 2005).