One reason for the rise in health care costs in the united states is the nation's rapidly expanding elderly population.

That statement is true

According to national institute of Aging, population aging is likely to influence the pattern of health care spending. The older a person is, the more concern and problems they have regarding their health, which cause an increase in their healthcare spending

This is a true statement but it is only one part of the puzzle. The fact is that the american population has been increasingly getting sick with different diseases or are just being prescribed different drugs which increase the burden on the taxpayers.