Rapid increase in the incidence of end-stage renal disease in patients with type 1 diabetes having HbA1c 10% or higher for 15 years

The incidence of end-stage renal disease (ESRD) in Japanese patients with type 1 diabetes mellitus (T1DM) was investigated regarding the association between mean HbA1c values during follow-up and the duration of follow-up/illness. The study includes 988 patients diagnosed at ages younger than 30 yr. These patients were initially examined between 1962 and 1999, and HbA1 and/or HbA1c measurements were taken for at least 3 yr after 1980. The follow-up period was from the date of the first HbA1 or HbA1c measurement to the final measurement day, or HbA1c measurement day immediately before the development of ESRD. The condition progressed to ESRD in 63 patients (mean duration of illness: 23.6 yr). Cox regression analysis revealed that patients with HbA1c of ≥ 10% had a significantly increased higher risk than those with HbA1c under 8% (P < 0.0001). The HbA1c cut-off point was 10.0%. The HbA1c value was ≥ 10% at baseline and during follow-up in 128 patients. Assuming that HbA1c of ≥ 10% persisted since the time of diagnosis in these patients, the cumulative incidence of ESRD abruptly increased after 15 yr of illness. Thus, the incidence of ESRD increased after the persistence of HbA1c of ≥ 10% for 15 yr.