Following the Classical Period ending in 600 CE, demographic statistics reflected both migrations and invading peoples. This resulted in new trade routes. This changed the demographic factors of employment for elements of the population related to new trading opportunities.
What specifically do you mean by "general Asia"? This is a very broad and unspecific term. Let us remember the continent of Asia is absolutely massive and stretches across vast territories. You might find it helpful to narrow down your research question and pick a particular zone or area. This might be important as I doubt there is much written record of demographics at this time.