Air Carrier First Officer reported the aft flight attendants were experiencing symptoms due to 'stuffy air' in the aft cabin. Captain initiated the QRH procedure to isolated the number 1 bleed system which improved the the air quality. The flight continued to a safe landing where crew conferred with Maintenance.

Narrative

In flight at FL370. Lead FA (Flight Attendant) called about 1/2 way into the flight and stated FA's in the back of [the aircraft] were experiencing headaches. We tried to gather information on the situation. They stated stuffy air in the back. Aircraft started out very warm from ZZZ but at that time it showed below 70 in the back. Forward FA was not experiencing any issues. MEL for HPV complicated the issue. It had opposing guidance to the fume event procedure and we weren't sure if that was what we were experiencing. I focused on flying the Aircraft and the radios while the CA (Captain) worked on the event. We doned our O2 masks when they didn't see an improvement in the cabin. CA isolated the number 1 bleed system and after some time they said they saw improvement in the back cabin. We discontinued the use of the masks after we had the report of improved air quality in the back. The lead FA never did experience any adverse effects. We continued the flight and landed in ZZZ1 with no other issues. We talked with the Cabin Crew and Maintenance about the event in detail.