How could "additions to the address book" affect the amount of spam you
receive?
You could not have added data to the address book. It contains no data. You
must have added it to your Contacts Folder which you can sort by any field
you want. Use View > Current View > Customize current view to get to the
Sort dialog. You can also add any field you want to a list view of your
Contacts and sort by that. Modified date would be what you want.