Risk of renal complications and death in young and middle-aged Swedes with parental type 1 diabetes: a nation-wide, prospective cohort study.

Introduction: This study aimed to investigate if individuals with childhood-onset type 1 diabetes having a parent with the same condition (parental diabetes) had worse metabolic control and an increased risk of death and renal failure compared with those with parents without type 1 diabetes (sporadic diabetes).

Research design and methods: We conducted a population-based cohort study using data from the Swedish Childhood Diabetes Register, including cases with onset of type 1 diabetes before the age of 15 and recorded between 1977 and 2010. The cohort was linked to national registers to compare mortality, renal failure, and glycated hemoglobin (HBA1c) levels.

Results: We identified 16 572 incident cases of childhood-onset type 1 diabetes. Of these, 15 701 had data on parental diabetes status, with 1390 (8.9%) having at least one parent with this condition. HbA1c data were available in 9105 individuals at 20-30 years of age, with the parental group showing higher levels compared with the sporadic diabetes group (8.4% (68 mmol/mol) vs 8.2% (66 mmol/mol), p=0.004). The Cox proportional HR for death in parental diabetes was 1.33 (95% CI 1.00 to 1.75), and the competing risk HR for renal failure was 1.27 (95% CI 1.08 to 1.50). Women in the parental diabetes group had a higher risk of early death (HR 1.79, 95% CI 1.17 to 2.72) compared with the sporadic diabetes group.

Conclusions: Individuals with parental diabetes had slightly higher HbA1c and elevated risks of renal failure and death compared with those with sporadic diabetes, especially pronounced in women. Although the exact mechanisms behind these differences are unclear, we suggest that individualized care may benefit individuals with parental type 1 diabetes.