Impaired vibration perception threshold and long-term mean HbA1c in patients with type 1 diabetes mellitus.

The impact of long-term glycaemic control, assessed as HbA1c for 5 years or more, on vibration perception threshold (VPT) in Type 1 (insulin-dependent) diabetes was investigated. Patients with diabetes onset before 31 years of age and with a diabetes duration of < 26 years were included. HbA1c was on average monitored over 9.2 years with 32 measurements. VPT was measured with biothesiometry on the big toes, and compared to non-diabetic reference values standardized for age and height. The biothesiometry readings in the group of 207 patients were elevated. The median z score (z-transformation of In (VPT)) was 1.4 in the diabetic population. Patients with HbA1c > 7.8% (highest quartile) had a relative risk of 9.2 (95% CI 3.5 < RR < 24.0) to be among the 10% with the highest z score for VPT, compared to patients with HbA1c < 7.8%. Stepwise forward linear regression analysis with the log normal of the VPT as dependent variable included age, HbA1c, height, body mass index, macroalbuminuria, and hypertension (> 140/90 mmHg or antihypertensive treatment) as explaining variables. In conclusion, impaired VPT was strongly associated with high long-term HbA1c.