Cause-specific mortality in a cohort of Brazilian patients with type 1 diabetes

To assess cause-specific mortality in a cohort of patients with type 1 diabetes (T1D) followed at an university hospital (tertiary level, Rio de Janeiro city) and an outpatient clinic (secondary level, Bauru city) both in Brazil's southeast, and associations of survival with gender, age at diagnosis, self-reported ethnicity and diabetes duration.

Our study is based on a cohort of patients with T1D whose vital status was determined as of December 31, 2015. The causes of mortality were determined by death certificates and outpatient clinic records.

Among 986 patients, (54.4%) females, (74.8%) Caucasians, 886 (89.9%) were alive, 62 (6.3%) had died, and in 38 (3.9%) the vital status was unknown. Median age at death [interquartile range] and diabetes duration until death were 30.0 [13] and 15.6 [10] years, respectively. Considering those who died (n = 62), most patients (about 70%) died from end-stage renal disease, macrovascular disease or acute complications of diabetes, mainly diabetic ketoacidosis. The other causes of mortality were infections, fatal accidents and non-diabetes-related. The standardized mortality ratio was 3.13 [2.35-4.08] in those aged under 40. In a multivariate Cox model, "age < 40 years" and "year of diagnosis" were the only significant variables with hazard ratios of 6.259 [(3.100-12.639), p < 0.001] and 0.915 [(0.880-0.951), p < 0.001], respectively.

Our study shows that patients with T1D had a threefold increase in mortality. The specific causes of mortality were mainly diabetes-related chronic complications; however, acute complications, especially diabetic ketoacidosis, persisted as an important cause of mortality.