Familial aggregation and heritability of childhood-onset and adult-onset type 1 diabetes: a Swedish register-based cohort study
Authors' conclusion
Adult-onset type 1 diabetes seems to have weaker familial aggregation and lower heritability than childhood-onset type 1 diabetes. This finding suggests a larger contribution of environmental factors to the development of type 1 diabetes in adults than in children and highlights the need to identify and intervene on such factors.
Study context
- Population
- Individuals born in Sweden 1982–2010 (Medical Birth Register) linked to parents, full siblings, half siblings and cousins (Multi-Generation Register); adult-onset T1D aged 19–30 years, childhood-onset aged 0–18 yearsborn in Sweden during study period
- Participants
- 2,943,832 individuals
- Exposure
- Family history of T1D vs none; adult-onset vs childhood-onset T1D
- Outcome
- Cumulative incidence and hazard ratios (HRs) of adult-onset and childhood-onset T1D by family history of T1D; heritability based on tetrachoric correlations using sibling pairs
Methodological detailsnationwide, Swedish registers, sibling pairs
- Nationwide
- Swedish registers
- Sibling pairs
Main finding
As reported in the abstract
HR for adult-onset T1D, first-degree relative with T1D
7.21
95% CI 6.28–8.28
HR for childhood-onset T1D, first-degree relative with T1D
9.92
9.38–10.50
Heritability, adult-onset T1D (lower)
0.56
0.45–0.66
Heritability, childhood-onset T1D
0.81
0.77–0.85
Observational data: associations, not effects.
Further findings
HR of T1D before age 30 years by onset age of the affected first-degree relative
- Relative developed T1D during adulthood (smaller HR)
- 6.68 [6.04-7.39]
- Relative developed T1D during childhood
- 10.54 [9.92-11.19]
T1D in other relatives
- Similar findings were observed for T1D in other relatives
Cases during follow-up
- Adult-onset T1D cases (median onset age 23.4 years, IQR 21.1-26.2)
- 3240
- Childhood-onset T1D cases (median onset age 9.8 years, 6.2-13.3)
- 17 914
- 2 832 755 in childhood-onset analysis; 1 805 826 in adult-onset analysis
Original publication
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