Clinical Characteristics and Development of Complications Differ Between Adult-Onset and Child-Adolescent-Onset Type 1 Diabetes: A Report From a Tertiary Medical Center in Türkiye.

Background and Aims: The age-at-onset is of great importance in the heterogeneity of Type 1 diabetes mellitus (T1DM). This study was designed to define clinical and laboratory differences between child-adolescent-onset and adult-onset T1DM at presentation and during follow-up and determine the predicting factors for developing microvascular and macrovascular complications. Material and Methods: This retrospective observational study evaluated T1DM patients who were followed in the diabetes outpatient clinic between January 1, 2000, and December 31, 2019. Results: The study cohort included 490 individuals with T1DM (54.3% female, 58.8% adult-onset, and median follow-up: 5 years). In the adult-onset group, baseline C-peptide and GADA prevalence were higher, whereas presentation with ketoacidosis was 2.3-fold lower compared to the child-adolescent-onset group (p < 0.001). During follow-up, the adult-onset group had a 2.4-fold higher overweight/obesity (p < 0.001) and 1.7-fold higher dyslipidemia/hyperlipidemia (p = 0.002) than the child-adolescent-onset group. In multivariate analysis, fasting glucose (p = 0.024) in adult-onset, dyslipidemia/hyperlipidemia (p = 0.037) in child-adolescent-onset, and diabetes duration (p = 0.008 and p = 0.007) and hypertension (p = 0.001 and p = 0.01) in both groups were associated with increased risk of microvascular complications, whereas age-at-onset (p = 0.024), dyslipidemia/hyperlipidemia (p = 0.03), nephropathy (p = 0.003), and neuropathy (p = 0.001) in adult-onset and age (p = 0.002) and triglycerides (p = 0.013) in child-adolescent-onset groups were associated with increased risk of macrovascular complications. The cutoff C-peptide levels at baseline predicted microvascular complications in the whole cohort and adult-onset group were defined as 0.383 ng/mL (p < 0.001) and 0.41 ng/mL (p = 0.001), respectively. In the Kaplan-Meier analysis, C-peptide (< 0.383 ng/mL) but not age-at-onset predicted future development of microvascular and macrovascular complications (p = 0.003 and p = 0.032). Conclusion: Clinical presentation and prognosis differ in adult-onset and child-adolescent-onset T1DM. Low initial C-peptide may predict the development of microvascular and macrovascular complications.