OBJECTIVE To evaluate whether autonomic neuropathy predicts deterioration in glomerular filtration rate in IDDM patients.

RESEARCH DESIGN AND METHODS A prospective study in which 35 IDDM patients have been followed for 10–11 yr. Autonomic nerve function tests included heart-rate reactions to deep breathing (expiration-to-inspiration ratio) and to tilt (acceleration and brake indexes). GFR was evaluated by the ⁵¹Cr-EDTA plasma clearance method.

RESULTS At entry to the study, no significant differences were noted in age (39 ± 2 [mean ± SE] vs. 42 ± 4 yr), duration of diabetes (20 ± 3 vs. 23 ± 4 yr), supine blood pressures (120/79 ± 3/2 mmHg vs. 121/78 ± 6/3 mmHg), and GFR (113 ± 6 vs. 107 ± 3 ml·min⁻¹·1.73 m⁻²) between 20 patients with and 15 without autonomic neuropathy (age-corrected criteria). After 10–11 yr, GFR had decreased significantly (22 ± 4 ml·min⁻¹·1.73 m⁻² P < 0.001) in patients with autonomic neuropathy but not (8 ± 5 ml·min⁻¹·1.73 m⁻², NS) in patients without. In keeping with this, GFR decreased more than expected (difference in GFR/ expected decrease in GFR) in patients with autonomic neuropathy, compared with those without (4.46 ± 0.98 vs. 0.48 ± 0.73, P < 0.005).

CONCLUSIONS Autonomic neuropathy predicts future deterioration in GFR in IDDM patients.