I was listening to a news program on the radio the other day, and it got me thinking.  The story (from a secular news program) was about an elderly married couple--the husband was in his early 90s and the wife was in her late 80s--and the care they chose to receive from their doctors.  Both people had several health conditions, but not that directly affected their day-to-day life.  They decided not to undergo "invasive" treatment, as it was described, like surgery or kidney dialysis, because while there was a chance it would increase their lifespan, they would spend a lot of time in hospitals and doctor's offices, they would be incapacitated for a period of time, and there was the ever present risk of something going wrong.  They decided instead to do less invasive things, such as medication, exercise, and some quick doctor's visits.  Most importantly to them, they were able to stay at home and stay together.  In the end, the husband had a heart attack, and was brought to a hospital to stabilize his condition.  Instead of getting surgery, once he was stabilized he was sent home, per his wishes, where he died a few days later.

This got me thinking, what is the Church's teaching on this?  I know, obviously, that euthanasia of old or sick people is gravely sinful, and is nothing less than murder.  I also know that common necessities of life, like food or water, cannot be withheld to hasten a person's death.  But what about what this couple did?  Is it ever OK to simply reject further "invasive" medical procedures, and let nature take its course?  Or, must one do whatever it possible to extend life?

There is a lot of good information in medical moral theology books.

I don't think there is one set answer because each situation is different, ordinary means change over time, and the means of the individual includes certain considerations.