TABLE 1

Subject characteristics of study population and incidence of type 1 diabetes in siblings

SiblingsPerson-yearsIncident cases of type 1 diabetes in siblingsIncidence per 10,000 person-years
Sex of the sibling
    Male5,202207,384367 (7.1)17.7 (15.9–19.6)
    Female4,966198,301280 (5.6)14.1 (12.5–15.9)
Family size
    One child (682 families)
    Two children (1606 families)1,60658,716106 (6.6)18.1 (14.8–21.8)
    Three children (1230 families)2,46094,854168 (6.8)17.7 (15.1–20.6)
    Four children (678 families)2,03481,012133 (6.5)16.4 (13.8–19.5)
    Five or more children (772 families)4,068171,102240 (5.9)14.0 (12.3–15.9)
    Total (4,968 families)10,168405,685647 (6.4)15.9 (14.7–17.2)
Birth year of the sibling
     <19605,151239,016259 (5.0)10.8 (9.6–12.24
    1960–19693,838137,337291 (7.6)21.2 (18.8–23.8)
    1970–197997125,78172 (7.4)27.9 (21.9–35.2)
    ≥19802083,55025 (12.0)70.4 (45.6–104.0)
Age at onset of type 1 diabetes in index case (years)
    0–41,30642,498160 (12.3)37.6 (32.0–44.0)
    5–92,811104,799213 (7.6)20.3 (17.7–23.2)
    10–144,156173,738203 (5.5)11.7 (10.1–13.4)
    ≥151,89584,64971 (3.7)8.4 (6.6–10.6)
  • Data are n (%) or n (95% CI).