CHAT and obstructive sleep apnea syndrome: In contrast to those in the OSA group, PGP9.5-positive (26.04 ± 7.41 vs. 90.00 ± 19.78×1000 μm2/mm2, P = 0.0001) (Fig 4J and 4K), TH-positive (8.18 ± 2.57 vs. 48.21 ± 12.22×1000 μm2/mm2, P <0.0001) (Fig 4L and 4M), and CHAT-positive (51.90 ± 12.70vs. 105.6 ± 18.57 ×1000 μm2/mm2, P = 0.0007) (Fig 4N and 4O) nerve densities were significantly increased.