The effect of 8 years of strict glycaemic control on peripheral nerve function in IDDM patients: the Oslo study

We have investigated the effect of long-term strict glycaemic control on peripheral and autonomic nerve function in 45 IDDM patients (age 18–42 years, diabetes duration 7–23 years) without clinical signs of neuropathy or other neurological disease. They were randomly assigned to treatment either with continuous insulin infusion, multiple injections (4–6 times daily), or conventional treatment (twice daily) for 4 years and followed prospectively for 8 years. Motor and sensory nerve conduction velocities were measured at the start and after 8 years. Autonomic nerve function tests were performed only once, after 8 years. A significant reduction of nerve conduction velocity was observed during 8 years in patients with mean HbA1 more than 10% (n=12, group mean 10.9%, range 10.1–13.2%) compared to patients with HbA1 less than 10% (n=33, group mean 9.0%, range 7.5–9.9%). Change of motor nerve conduction velocity in the peroneal nerve was: −4.8±4.9 (SD) vs −2.2±5.3 m/s (p<0.01). Change of motor nerve conduction velocity in the posterior tibial nerve was: −6.8±5.7 vs −3.9±5.1 m/s (p<0.05). No significant changes were observed in the ulnar nerve. Change of sensoric nerve conduction velocity in the sural nerve was: −8.9±8.0 vs −4.6±5.3 m/s (p<0.05). Multiple regression analysis showed that a change in HbA1 of 1% resulted in a 1.3 m/s change in nerve conduction velocity during 8 years. A significantly lowered heart-rate variation during deep breathing (p<0.05) and heart-rate response to standing (p<0.01) was found in patients with HbA1 more than 10% compared to patients with HbA1 less than 10%. This study confirms that the long-term lowering of blood glucose retards the deterioration in nerve conduction velocity observed in the diabetic nerve.