Because onset of autonomic neural dysfunction in the diabetic syndrome has not 
been well established, sensitive and quantitative measures of autonomic nervous 
system (ANS) function were made in 19 non-insulin-dependent (NIDD) and 14 
insulin-dependent (IDD) recent-onset diabetic subjects. The known duration of 
diabetes mellitus in the NIDD subjects was less than or equal to 12 mo. The 
duration in the IDD subjects was less than or equal to 24 mo. RR-variation 
during beta adrenergic blockade (an index of an ANS reflex involving the cardiac 
parasympathetic nervous system [PNS] pathway) was smaller than that of control 
subjects in both NIDD (P less than 0.001) and IDD subjects (P less than 0.01). 
This PNS abnormality was not likely to be due to volume depletion since acute 
volume depletion induced by furosemide in six normal subjects (1608 +/- 105 ml, 
mean +/- SEM) did not change RR-variation. Dark-adapted pupil size after topical 
PNS blockade (an index of iris sympathetic nervous system [SNS] activity) was 
also smaller in both groups of diabetic subjects (NIDD, P less than 0.01; IDD, P 
less than 0.05). Pupillary latency time (an index of an ANS reflex involving 
iris PNS pathway) was prolonged in the NIDD subjects (P less than 0.005) but was 
not significantly altered in the IDD subjects. Thus, it would appear that the 
ANS is impaired soon after the diagnosis of diabetes mellitus. We hypothesize 
that early impairment of the ANS is common in IDD and NIDD subjects. This 
finding is consistent with the hypothesis that abnormal carbohydrate metabolism 
is an important factor in the etiology of diabetic autonomic neuropathy.