There are different kinds of ghosts, though I personally don't know their effect on whether they die or not. For one ghosts can be dead sims, or they could be born as a ghost. The Supernatural expansion pack also allows ghosts to be created. Then there are the different types of dead Sim ghosts, such as from old age, electrocution, fire, drowning, etc. I take it your ghost is a sim that died of old age, which would be the answer to Pam's question.