Mortality of childhood-onset IDDM patients - A cohort study in Havana City province, Cuba

OBJECTIVE - To determine the survival pattern and the underlying cause of death in a cohort of childhood-onset IDDM subjects from Havana City Province, Cuba. RESEARCH DESIGN END METHODS - This was a descriptive study carried out on a historical cohort of IDDM subjects with disease onset before 15 years of age in Havana City Province, Cuba. The cohort was assembled from several sources. Subjects were diagnosed from 1965 to 1980, and their vital status was assessed at 31 December 1991. Cumulative survival rate was calculated by the Kaplan-Meier method, and a univariate analysis was performed. To test survival differences between groups, the Cox-Mantel test was used. To compare the cohort mortality with the general population, standardized mortality ratios by sex and age were calculated. Specific causes of death were determined by a committee examining death certificates, clinical records, and necropsy reports. RESULTS - A total of 504 subjects were identified, and the mean follow-up time was 17.5 years. Of the subjects, 70 (13.9%) had died at 31 December 1991. Overall, the cohort had a 71% cumulative survival rate at 25 years of IDDM duration. There were no survival differences according to sex or calendar period of IDDM diagnosis. Statistically significant differences were found among age-at-diagnosis groups. The group with a peripubertal age at diagnosis showed the worst prognosis. The cohort experienced 8.5 times the all-causes death rate, compared with the general population. Renal disease accounted for almost half the deaths. CONCLUSIONS - IDDM subjects from Havana City Province, Cuba, showed a better survival pattern than IDDM subjects from other developing countries. However, when compared with IDDM populations from developed countries, there is a survival reserve to be achieved by reducing mortality due to renal disease and infections.