SAN DIEGO – Life expectancy of patients with type 1 diabetes has improved dramatically since 1950, results from a long-term prospective study have shown.
According to the Pittsburgh Epidemiology of Diabetes Complications (EDC) Study, life expectancy at birth for those diagnosed with type 1 diabetes during 1965-1980 was 68.8 years, or about 4 years less than that of a comparable cohort of the U.S. general population, while life expectancy for those diagnosed during 1950-1964 was 53.4 years, or about 18 years less than that of a comparable cohort of the general population.
"Individuals with childhood-onset diabetes do not represent a major insurance risk and should be minimally penalized, if at all, in terms of life insurance and other mortality-based decisions," Dr. Trevor J. Orchard said at the annual scientific sessions of the American Diabetes Association.
While numerous other studies have shown that mortality in type 1 diabetes has been decreasing in recent decades, "how this currently translates into improved life expectancy in the United States was not clear," said Dr. Orchard, professor of epidemiology, pediatrics, and medicine at the University of Pittsburgh.
The objective of the current study was to compare the life expectancy among two different cohorts of patients enrolled in the Pittsburgh EDC Study, which is a prospective study of childhood-onset type 1 diabetes. Of the 933 patients, 390 were diagnosed or seen within 1 year of diagnosis at Children’s Hospital of Pittsburgh during 1950-1964 (cohort 1), while 543 were diagnosed or seen within a year of diagnosis during 1965-1980 (cohort 2). Half of the participants were female, and their mean age at diagnosis was 8 years. All were followed through 2009.
To ascertain mortality, the researchers used death certificates and hospital, autopsy, and coroner reports. They used Kaplan-Meier curves and the log-rank statistic to determine differences in survival benefits between the cohorts, and constructed abridged life tables to calculate life expectancy.
Dr. Orchard reported that the 30-year mortality for patients in cohort 1 was 35% compared with 12% for those in cohort 2, a statistically significant difference. Similarly, the life expectancy at birth for those in cohort 1 was estimated to be 53.4 years compared with 68.8 years for those in cohort 2, a difference of about 15 years (P less than .0001). This persisted regardless of sex or pubertal status at diagnosis of diabetes.
The life expectancy of cohort 2 is 3.6 years less than that estimated for a comparable cohort of the U.S. general population (72.4 years), Dr. Orchard said, while the life expectancy of cohort 1 is about 18 years less than that of a comparable cohort of the general population (71.5 years).
Reasons for the improvement in life expectancy between the two cohorts are multifactorial, he said, including the development of blood glucose self-monitoring and the use of the hemoglobin A1c test, which was not available in cohort 1.
"It’s difficult to partition the exact reasons for the changes, but the major improvement in terms of complications has been in renal disease," Dr. Orchard said. "Cardiovascular disease is not improving in these patients as dramatically as renal disease."
Dr. Orchard disclosed that he is a consultant for AstraZeneca and Abbott Laboratories, received research support from VeraLight, and has inherited Bristol-Myers Squibb stock