Skip to main content

Table 1 Characteristics of children by type 1 diabetes status in different study designsa

From: Maternal smoking during pregnancy and type 1 diabetes in the offspring: a nationwide register-based study with family-based designs

  Cohort analysis Cousin analysis Sibling analysis
No type 1 diabetes Type 1 diabetes Not any diabetes Type 1 diabetes Not any diabetes Type 1 diabetes
Overall 2,976,704 (99.4) 18,617 (0.6) 21,036 (72.5) 7988 (27.5) 21,302 (59.9) 14,284 (40.1)
Boys 1,529,498 (51.4) 10,166 (54.6) 10,729 (51.0) 4399 (55.1) 10,908 (51.2) 7816 (54.7)
Year of birth
 1983–1984 164,968 (5.5) 888 (4.8) 1141 (5.4) 302 (3.8) 799 (3.8) 451 (3.2)
 1985–1989 469,384 (15.8) 2811 (15.1) 3800 (18.1) 12,203 (15.1) 3537 (16.6) 2053 (14.4)
 1990–1994 534,392 (18.0) 3892 (20.9) 4918 (23.4) 1849 (23.1) 5038 (23.7) 3236 (22.7)
 1995–1999 407,468 (13.7) 3404 (18.3) 3769 (17.9) 1476 (18.5) 4192 (19.7) 2790 (19.5)
 2000–2004 421,330 (14.2) 3533 (19.0) 3436 (16.3) 1531 (19.2) 3782 (17.8) 2842 (19.9)
 2005–2009 468,632 (15.7) 2696 (14.5) 2624 (12.5) 1090 (13.6) 2656 (12.5) 2032 (14.2)
 2010–2014 510,530 (17.2) 1393 (7.5) 1348 (6.4) 537 (6.7) 1298 (6.1) 80 (6.2)
Gestational age in days, mean (SD) 278.8 (12.2) 277.9 (12.2) 278.4 (12.4) 278.0 (12.0) 278.3 (12.0) 278.0 (12.0)
Birth weight for gestational age
 Small for gestational age 70,763 (2.4) 382 (2.1) 466 (2.2) 167 (2.1) 388 (1.8) 267 (1.9)
 Normal 2,793,435 (93.8) 17,350 (93.2) 19,663 (93.5) 7466 (93.5) 19,783 (92.9) 13,316 (93.2)
 Large for gestational age 103,661 (3.5) 834 (4.5) 850 (4.0) 337 (4.2) 1066 (5.0) 666 (4.7)
 Unknown 8845 (0.3) 51 (0.3) 57 (0.3) 18 (0.2) 65 (0.3) 35 (0.2)
Birth order
 1 1,265,549 (42.5) 7851 (42.2) 8667 (41.2) 3273 (41.0) 7523 (35.3) 5203 (36.4)
 2 1,082,395 (36.4) 6833 (36.7) 7545 (35.9) 2966 (37.1) 7617 (35.8) 5796 (40.6)
 3 +  628,760 (21.1) 3933 (21.1) 4824 (22.9) 1749 (21.9) 6162 (28.9) 3285 (23.0)
Maternal age at delivery in years, mean (SD) 29.7 (5.2) 29.7 (5.1) 28.8 (5.1) 29.4 (5.1) 29.0 (5.1) 29.5 (5.0)
Maternal marital status
 Living with child’s father 2,751,651 (92.4) 17,282 (92.8) 19,354 (92.0) 7420 (92.9) 19,788 (92.9) 13,362 (93.5)
 Single 56,402 (1.9) 330 (1.8) 452 (2.1) 151 (1.9) 347 (1.6) 227 (1.6)
 Others 89,494 (3.0) 482 (2.6) 641 (3.0) 196 (2.5) 553 (2.6) 293 (2.1)
 Unknown 79,157 (2.7) 523 (2.8) 589 (2.8) 221 (2.8) 614 (2.9) 402 (2.8)
Maternal educational level
 Pre-secondary 386,663 (13.0) 2343 (12.6) 2799 (13.3) 980 (12.3) 2705 (12.7) 1600 (11.2)
 Upper-secondary 567,201 (19.1) 4343 (23.3) 5282 (25.1) 2105 (26.4) 5108 (24.0) 3459 (24.2)
 High school 567,452 (19.1) 3573 (19.2) 3684 (17.5) 1495 (18.7) 3764 (17.7) 2736 (19.2)
 Post-secondary or higher 914,211 (30.7) 5387 (28.9) 5018 (23.9) 2127 (26.6) 5547 (26.0) 4198 (29.4)
 Unknown 541,177 (18.2) 2971 (16.0) 4253 (20.2) 1281 (16.0) 4178 (19.6) 2291 (16.0)
Paternal educational level
 Pre-secondary 492,235 (16.5) 2975 (16.0) 3597 (17.1) 1258 (15.7) 3213 (15.1) 2098 (14.7)
 Upper-secondary 716,097 (24.1) 5451 (29.3) 62,200 (29.5) 2491 (31.2) 6296 (29.6) 4334 (30.3)
 High school 547,304 (18.4) 3226 (17.3) 3287 (15.6) 1344 (16.8) 3312 (15.5) 2372 (16.6)
 Post-secondary or higher 785,763 (26.4) 4607 (24.7) 4347 (20.7) 1828 (22.9) 5002 (23.5) 3645 (25.5)
 Unknown 435,305 (14.6) 2358 (12.7) 3605 (17.1) 1067 (13.4) 3479 (16.3) 1835 (12.8)
Maternal BMI in kg/m2 during pregnancyb, mean (SD) 23.9 (4.3) 24.1 (4.3) 23.9 (4.3) 24.2 (4.3) 24.1 (4.5) 24.1 (4.3)
Maternal cesarean section at delivery 399,662 (13.4) 2724 (14.6) 2595 (12.3) 1107 (13.9) 2576 (12.1) 1890 (13.2)
Maternal diabetes at childbirthc 24,923 (0.8) 593 (3.2) 340 (1.6) 256 (3.2) 560 (2.6) 392 (2.7)
Paternal diabetes at childbirth 21,731 (0.7) 865 (4.6) 123 (0.6) 371 (4.6) 760 (3.6) 623 (4.4)
Maternal asthma at childbirth 158,268 (5.3) 1085 (5.8) 1093 (5.2) 475 (5.9) 1141 (5.4) 815 (5.7)
Paternal asthma at childbirth 35,258 (1.2) 237 (1.3) 202 (1.0) 114 (1.4) 259 (1.2) 171 (1.2)
  1. SD standard deviation, BMI body mass index
  2. aValues are presented as numbers (proportions [%]) unless stated otherwise
  3. bAt first antenatal visit, mostly during 8–12 weeks of pregnancy
  4. cAny type of diabetes but not gestational diabetes