The ever excellent Ed West has this to say over at Telegraph blogs, while speaking about our current decline:

There are, of course, many other similarities between our age and the late Roman Empire: a declining birth rate, especially marked among upper-class women; a collapse in religious belief and the growth of a more vital and passionate monotheistic faith from the Middle East; a shrunken attachment to the ideal of the country – patriotism – and increased attachment to the state, a state which virtually all ambitious, educated people wished to work for.