IOS new Thread or run background in foreground ?

Hello

my question for IOS only

i need to start new thread ( background ) have nothing with UI or start background service while application is running is IOS how ?

I've tried Ti.worker but its not background thread its foreground thread .

the reason i need this request i dealing with Ti.Contacts.getAllPeople() , and some phones has over 5K contacts and when i loop over 5K contacts the UI got lagged and stop working until loop is complete .

is there anyway to loop Ti.Contacts.getAllPeople() as pagenation or in background or thread when app is running ?