Will Removing Threads 4 Years Post Thread Lift Cause Jowl to Sag?

After several months the threads which repositioned the jowls and deeper structures have done their job. Scar tissue has secured these structures in their new position and are not needed any more.

It is difficult to know for sure but usually thread lift longevity is not more than 2 years. The reason why is the tissue that the threads suspend weakens or the threads pull through. Removing these threads at this point will USUALLY not cause significant changes in the way you look.
You should have a clear discussion with your plastic surgeon and be prepared that, while unikely, there may be changes after the threads are removed.

Hello!
What type of threads do you have currently? Typically, threads dissolve on their own from 12-36 months post-procedure. It would be helpful to know what material of thread was used.
With Love & Gratitude,Jordan Jacobs, RN, CANSOwner/CEOAesthetic Injector

Dear Irsa,
I would go with what your doctor says.
I am sure if you require facelift, your doctor would have advised it. 
Post threadlift, it is the new collagen produced that helps to firm and tighten your skin. That is something that stays with you, with or without the threads.
I hope this helps!

I am not a plastic surgeon but as a cosmetic dermatologist knowledgable in facial anatomy and skin biology, I am not surprised that your physician wants to remove the threads that would interfere with your planned surgical procedure.  Remember that a surgical neck lift will reorient that skin -- your prior threads which were hidden, could easily become visible.  In addition, as foreign bodies in the new surgical site you could be a set up for a new inflammatory reaction or infection.Discuss your concerns with your physician.  Confirm the reasons for the planned removal. Ask if he is removing all of your threads or just the ones in the lower face and neck.  Either he or his staff should be able to answer your questions.I hope this answers your question. Best wishes.