Baseline patient characteristics
| ARC | Atopic eczema | Asthma | ||||
| Exposed | Unexposed | Exposed | Unexposed | Exposed | Unexposed | |
| Subjects | 782 320 | 1 291 550 | 1 393 570 | 2 170 618 | 1 049 868 | 1 732 480 |
| Age at allergy diagnosis years | 29.89±19.74 | 24.25±25.29 | 25.09±21.95 | |||
| Age years | 36.44±19.44 | 38.14±19.11 | 29.77±25.30 | 32.74±25.45 | 35.61±21.26 | 37.98±20.91 |
| Age categories | ||||||
| 0–9 years | 56 995 (7.29) | 78 503 (6.08) | 443 272 (31.81) | 602 343 (27.75) | 110 635 (10.54) | 142 078 (8.20) |
| 10–19 years | 97 289 (12.44) | 125 135 (9.69) | 152 580 (10.95) | 191 030 (8.80) | 146 137 (13.92) | 184 127 (10.63) |
| 20–29 years | 156 848 (20.05) | 247 795 (19.19) | 176 608 (12.67) | 277 761 (12.80) | 218 329 (20.80) | 356 637 (20.59) |
| 30–39 years | 165 941 (21.21) | 292 551 (22.65) | 157 265 (11.29) | 272 643 (12.56) | 178 980 (17.05) | 323 138 (18.65) |
| 40–49 years | 115 694 (14.79) | 209 110 (16.19) | 126 174 (9.05) | 226 457 (10.43) | 126 552 (12.05) | 234 123 (13.51) |
| 50–59 years | 78 520 (10.04) | 141 956 (10.99) | 10 9781 (7.88) | 198 495 (9.14) | 98 207 (9.35) | 182 006 (10.51) |
| 60–69 years | 58 414 (7.47) | 103 498 (8.01) | 96 955 (6.96) | 171 496 (7.90) | 81 459 (7.76) | 147 338 (8.50) |
| ≥70 years | 52 619 (6.73) | 93 002 (7.20) | 130 935 (9.40) | 230 393 (10.61) | 89 569 (8.53) | 163 033 (9.41) |
| Sex | ||||||
| Male | 368 819 (47.14) | 632 521 (48.97) | 639 277 (45.87) | 1 002 759 (46.20) | 502 841 (47.90) | 844 310 (48.73) |
| Female | 413 501 (52.86) | 659 029 (51.03) | 754 293 (54.13) | 1 167 859 (53.80) | 547 027 (52.10) | 888 170 (51.27) |
| BMI kg·m−2 | 25.94±5.26 | 25.82±5.31 | 26.14±5.43 | 25.98±5.33 | 26.74±6.01 | 25.83±5.35 |
| BMI categories | ||||||
| Underweight (<18.5 kg·m−2) | 13 778 (1.76) | 24 658 (1.91) | 18 525 (1.33) | 32 012 (1.47) | 18 722 (1.78) | 32 606 (1.88) |
| Normal weight (18.5–25 kg·m−2) | 240 550 (30.75) | 391 963 (30.35) | 296 729 (21.29) | 485 257 (22.36) | 273 231 (26.03) | 488 611 (28.20) |
| Overweight (25–30 kg·m−2) | 167 639 (21.43) | 260 249 (20.15) | 215 020 (15.43) | 345 277 (15.91) | 205 041 (19.53) | 323 882 (18.69) |
| Obese (>30 kg·m−2) | 95 186 (12.17) | 148 894 (11.53) | 131 161 (9.41) | 200 892 (9.26) | 156 489 (14.91) | 189 050 (10.91) |
| Missing | 265 167 (33.89) | 465 786 (36.06) | 732 135 (52.54) | 1 107 180 (51.01) | 396 385 (37.76) | 698 331 (40.31) |
| Smoker categories | ||||||
| Nonsmoker | 393 523 (50.30) | 581 795 (45.05) | 472 948 (33.94) | 762 193 (35.11) | 454 001 (43.24) | 735 619 (42.46) |
| Ex-smoker | 103 476 (13.23) | 158 144 (12.24) | 151 830 (10.90) | 228 211 (10.51) | 153 849 (14.65) | 198 447 (11.45) |
| Current smoker | 117 214 (14.98) | 255 481 (19.78) | 181 665 (13.04) | 304 165 (14.01) | 202 006 (19.24) | 329 486 (19.02) |
| Missing | 168 107 (21.49) | 296 130 (22.93) | 587 127 (42.13) | 876 049 (40.36) | 240 012 (22.86) | 468 928 (27.07) |
| Ethnicity | ||||||
| Caucasian | 276 634 (35.36) | 419 125 (32.45) | 501 207 (35.97) | 737 165 (33.96) | 398 059 (37.92) | 543 068 (31.35) |
| Black Afro-Caribbean | 16 551 (2.12) | 18 529 (1.43) | 19 286 (1.38) | 26 148 (1.20) | 9608 (0.92) | 18 120 (1.05) |
| South Asian | 23 375 (2.99) | 27 075 (2.10) | 33 686 (2.42) | 38 714 (1.78) | 15 577 (1.48) | 25 656 (1.48) |
| Mixed Race/Chinese/Other | 15 467 (1.98) | 20 857 (1.61) | 22 697 (1.63) | 33 153 (1.53) | 11 179 (1.06) | 22 258 (1.28) |
| Missing | 450 293 (57.56) | 805 964 (62.40) | 816 694 (58.60) | 1 335 438 (61.52) | 615 445 (58.62) | 1 123 378 (64.84) |
| Townsend deprivation quintile | ||||||
| 1 (most affluent) | 173 514 (22.18) | 267 708 (20.73) | 298 714 (21.44) | 446 876 (20.59) | 189 932 (18.09) | 332 379 (19.19) |
| 2 | 143 591 (18.35) | 230 699 (17.86) | 253 849 (18.22) | 391 908 (18.06) | 178 000 (16.95) | 307 500 (17.75) |
| 3 | 14 0876 (18.01) | 238 640 (18.48) | 252 724 (18.14) | 398 279 (18.35) | 193 512 (18.43) | 324 160 (18.71) |
| 4 | 123 684 (15.81) | 215 294 (16.67) | 227 134 (16.30) | 362 669 (16.71) | 189 185 (18.02) | 298 135 (17.21) |
| 5 (most deprived) | 87 912 (11.24) | 154 989 (12.00) | 160 308 (11.50) | 256 742 (11.83) | 189 185 (13.33) | 212 347 (12.26) |
| Missing | 112 743 (14.41) | 184 220 (14.26) | 200 841 (14.41) | 314 144 (14.47) | 159 252 (15.17) | 257 959 (14.89) |
| Autoimmune disorders at baseline | ||||||
| Systemic lupus erythematosus | 791 (0.10) | 1195 (0.09) | 1445 (0.10) | 1610 (0.07) | 1064 (0.10) | 1514 (0.09) |
| Sjögren's syndrome | 516 (0.07) | 511 (0.04) | 693 (0.05) | 813 (0.04) | 572 (0.05) | 735 (0.04) |
| Vitiligo | 2191 (0.28) | 2516 (0.19) | 3532 (0.25) | 3519 (0.16) | 1996 (0.19) | 2895 (0.17) |
| Rheumatoid arthritis | 3819 (0.49) | 6122 (0.47) | 6933 (0.50) | 10 321 (0.48) | 6310 (0.60) | 8576 (0.50) |
| Psoriasis | 20 077 (2.57) | 28 648 (2.22) | 40 319 (2.89) | 39 147 (1.80) | 24 362 (2.32) | 35 489 (2.05) |
| Pernicious anaemia | 1458 (0.19) | 2095 (0.16) | 2879 (0.21) | 4101 (0.19) | 2464 (0.23) | 3166 (0.18) |
| Myasthenia gravis | 180 (0.02) | 256 (0.02) | 251 (0.02) | 460 (0.02) | 273 (0.03) | 349 (0.02) |
| Inflammatory bowel disease | 5003 (0.64) | 7030 (0.54) | 7848 (0.56) | 9537 (0.44) | 6428 (0.61) | 8843 (0.51) |
| Coeliac disease | 1824 (0.23) | 2141 (0.17) | 2876 (0.21) | 3221 (0.15) | 2398 (0.23) | 2770 (0.16) |
| Autoimmune thyroiditis | 2069 (0.26) | 2586 (0.20) | 2528 (0.18) | 3456 (0.16) | 2291 (0.22) | 3215 (0.19) |
| Multiple sclerosis | 1479 (0.19) | 2474 (0.19) | 2204 (0.16) | 3439 (0.16) | 1519 (0.14) | 3147 (0.18) |
Data are presented as n, mean±sd or n (%). ARC: allergic rhinitis/conjunctivitis; BMI: body mass index.