  We consider spatial correlation lengths \xi for various QCD light quark
bilinears at temperatures above a few hundred MeV. Some of the correlation
lengths (such as that related to baryon density) coincide with what has been
measured earlier on from glueball-like states; others do not couple to
glueballs, and have a well-known perturbative leading-order expression as well
as a computable next-to-leading-order correction. We determine the latter
following analogies with the NRQCD effective theory, used for the study of
heavy quarkonia at zero temperature: we find (for the quenched case) \xi^{-1} =
2 \pi T + 0.1408 g^2 T, and compare with lattice results. One manifestation of
U_A(1) symmetry non-restoration is also pointed out.
