The influence of autonomic neuropathy on cough reflex sensitivity in children with diabetes mellitus type 1.

Diabetic autonomic neuropathy (DAN) is manifested by dysfunction of one or more organ systems. Its subclinical form (sDAN) can be recognized with the use of noninvasive cardiovascular reflex tests. As the cough reflex is mediated via autonomic nervous system, there is a reason to suppose that it can also be changed due to presence of sDAN. The aim of the present study was to assess cough reflex sensitivity (CRS) in diabetic children with and without sDAN. A CRS test was performed in 35 children suffering from diabetes mellitus type 1 and the results were compared with those from age-matched 27 healthy children. Cough was induced by inhalation of capsaicin aerosol in doubling concentrations (0.61-1250 micromol/l) for 400 ms each. CRS was defined as the lowest capsaicin concentration that evoked 2 or more coughs (C2 parameter) and 5 or more coughs (C5 parameter). We found that CRS in the whole group of diabetic children was not significantly different from that in healthy children [diabetic children--C2: 75.1 micromol/l (95% CI: 42.0-134.2 micromol/l)] vs. healthy children--C2: 72.4 micromol/l (95% CI: 75.7-644.8 micromol/l)]. However, a significant decrease (P=0.005) in CRS was found in diabetic children with sDAN [n=12; C2: 221.0 micromol/l (95% CI: 75.7-644.8 micromol/l)] compared with diabetic children without sDAN [(n=23; C2: 42.7 micromol/l (95% CI: 23.1-79.0 micromol/l)]. We conclude that testing cough reflex sensitivity might be a way to establish the presence of diabetic neuropathy.