Patients with type 1 diabetes have an improved prognosis with regard to end-stage renal disease over the past four decades, and it appears the incidence of end-stage renal disease is lower than previously estimated, according to a study in the October 12 issue of JAMA: The Journal of the American Medical Association.
Diabetic kidney disease is one of the most severe complications of type 1 diabetes, and diabetes is the most important cause of end-stage renal disease (ESRD; severely impaired kidney function, requiring dialysis) in industrialized countries, according to background information in the article. Data on patients' risk of developing ESRD are sparse. Large population-based studies with long-term follow-up have not been performed; therefore, the true incidence and age- and sex-stratified risk estimates of ESRD among patients with type 1 diabetes are not known.
Patrik Finne, M.D., Ph.D., of Helsinki University, Finland, and colleagues estimated the long-term risk of ESRD and death in patients with type 1 diabetes and assessed how age at diagnosis of diabetes, time period of diagnosis, and sex affect these risks. The study included patients younger than 30 years at the time of being diagnosed with type 1 diabetes in Finland in 1965-1999 (n = 20,005), who were identified from the Finnish Diabetes Register. The group was followed from diagnosis of diabetes until development of ESRD (dialysis or kidney transplantation as identified from the Finnish Registry for Kidney Diseases), death, or end of follow-up on December 31, 2001.
The median follow-up time after diagnosis was 16.7 years, with a maximum of 37 years. During the follow-up period, there were 632 cases of ESRD and 1,417 deaths. The researchers found that the cumulative incidence among all type 1 diabetic patients was 2.2 percent at 20 years and 7.8 percent at 30 years after diagnosis. Patients of both sexes diagnosed as having type 1 diabetes before age 5 years had a smaller risk of developing ESRD (3.3 percent after 30 years) than other patients (8.4 percent). The risk of ESRD was lower for patients diagnosed as having type 1 diabetes in later years. The risk did not differ significantly between sexes.
Patients with ESRD had 13.1 times the risk of death compared with other patients with type 1 diabetes when adjusting for age, sex, and time period of diabetes diagnosis. "This emphasizes the severity of ESRD as a complication of diabetes," the authors write. The cumulative death rate was 6.8 percent at 20 years and 15.0 percent at 30 years after diagnosis of type 1 diabetes. The cumulative risk of dying with ESRD was 0.7 percent at 20 years and 3.3 percent at 30 years after diagnosis of type 1 diabetes. The risk of death increased with age at diagnosis. The time period for the diagnosis of diabetes strongly affected survival: patients with diagnosis in 1975-1979 had 48 percent lower risk of dying than those with diagnosis in 1965-1969.
"In conclusion, our data indicate improved prognosis of type 1 diabetes with regard to both ESRD and death," the researchers write. "The overall incidence of ESRD appears to be lower than previously reported."