Is the problem of the 21st century an aging population without workers to support it?

We hear a lot about population increases and how much stress that puts on our environment and resources, but what about the potential for population decline? It’s a problem I’ve wondered about for years given the fact that so much of the world’s current population increase, especially in the industrialized world, is as a result of aging rather than children being born. What happens as the population grows by aging even as the working age population shrinks dramatically?