Table 1

Baseline characteristics

ExposedUnexposed
Number of patients (n)2 491 0863 120 719
Number of patients with asthma diagnosis (n)472 984289 969
Number of patients with eczema diagnosis (n)455 348367 786
Median (IQR) follow-up period (person years)5.10 (2.02–9.68)4.11 (1.59–8.37)
Mean (SD) age at cohort entry (years)39.42 (23.65)35.81 (22.17)
Sex (n)
 Male1 129 9541 561 074
 Female1 361 1321 559 645
Body mass index, n (%)
 Underweight (<18.5 kg/m2)40 490 (1.63)52 235 (1.67)
 Normal (18.5–24.9 kg/m2)687 723 (27.61)823 574 (26.39)
 Overweight (25.0–29.9 kg/m2)541 784 (21.75)559 329 (17.92)
 Obese (>30.0 kg/m2)348 395 (13.99)310 123 (9.94)
 Not available872 694 (35.03)1 375 458 (44.08)
Smoking status, n (%)
 Current smoker348 532 (13.99)474 771 (15.21)
 Non-current smoker1 574 697 (63.21)1 681 583 (53.88)
 Not available567 857 (22.80)964 365 (30.90)
Drinking status, n (%)
 Current Drinker1 266 898 (50.86)1 394 975 (44.70)
 Non-current drinker370 169 (14.86)382 726 (12.26)
 Not available854 019 (34.28)1 343 018 (43.04)
Townsend index, n (%)
 (Least deprived) 1535 228 (21.49)657 580 (21.07)
 2464 489 (18.65)552 877 (17.72)
 3453 156 (18.19)559 350 (17.92)
 4388 862 (15.61)487 367 (15.62)
 5262 946 (10.56)327 038 (10.48)
 Not available386 405 (15.51)536 507 (17.19)
Ethnicity, n (%)
 White1 050 939 (42.19)1 114 783 (35.72)
 Black45 742 (1.84)51 975 (1.67)
 South Asian66 060 (2.65)74 028 (2.37)
 Mixed16 818 (0.68)19 858 (0.64)
 Other37 641 (1.51)54 616 (1.75)
 Missing1 273 886 (51.14)1 805 459 (57.85)