BTBD9 and restless legs syndrome: The lead variants at these three loci are in strong to modest LD with the previously reported variants associated with restless legs syndrome (rs113851554, MEIS1, P = 2 × 10−35, LD r2 = 1.00; rs12991815, C1D, P = 2 × 10−9, LD r2 = 0.96; rs9369062, BTBD9, P = 9 × 10−14, LD r2 = 0.49).