Does a stroke affect life expectancy?

Strokes can kill. For your mother to have had such a severe stroke at a relatively young age suggests there may be a higher risk for her to have another. There is also a higher risk that she will certain other types of illness, such as pneumonia. You haven't mentioned what kind of stroke it was (clot or hemmoragic) but the former is more treatable. You should have a chat with her physician, is he/she is willing.