Distribution of potential confounding variables by exposure category. Unless otherwise stated, figures are numbers (percentages)
| Quintile of Der p 1 exposure | Quintile of Fel d 1 exposure | |||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 1 (low) (n = 109) | 2 (n = 109) | 3 (n = 110) | 4 (n = 109) | 5 (high) (n = 109) | p (trend) | 1 (low) (n = 109) | 2 (n = 109) | 3 (n = 110) | 4 (n = 109) | 5 (high) (n = 109) | p (trend) | |
| *Test for independence. SPT, skin prick test; SEC, socioeconomic class. | ||||||||||||
| Median (range) allergen (μg/g dust) | 0.1 (0.02–0.3) | 0.5 (0.3–0.8) | 1.3 (0.8–2.2) | 4.3 (2.2–7.9) | 17.5 (8.0–385.0) | 0.2 (0.01–0.5) | 0.7 (0.5–1.1) | 1.9 (1.1–3.5) | 10.1 (3.6–47.8) | 140.5 (47.8–2799.8) | ||
| Median (range) weight unsieved dust | 0.2 (0.01–1.5) | 0.2 (0.003–1.6) | 0.2 (0.003–1.0) | 0.2 (0.006–1.3) | 0.2 (0.001–1.1) | 0.660 | 0.3 (0.01–1.6) | 0.2 (0.003–1.2) | 0.2 (0.003–1.3) | 0.1 (0.001–1.3) | 0.2 (0.01–0.9) | 0.001 |
| SPT +ve | 6 (5.5) | 16 (14.7) | 12 (10.9) | 12 (11.0) | 6 (5.5) | 0.093* | 8 (7.3) | 7 (6.5) | 11 (10.0) | 13 (11.9) | 8 (7.3) | 0.582* |
| Atopic wheeze | 5 (4.6) | 8 (7.3) | 12 (10.9) | 6 (5.5) | 7 (6.4) | 0.402* | 6 (5.5) | 9 (8.3) | 7 (6.4) | 10 (9.2) | 7 (6.4) | 0.825* |
| Maternal atopy | 29 (26.6) | 40 (37.0) | 41 (37.3) | 31 (28.4) | 41 (37.6) | 0.346 | 34 (31.2) | 35 (32.1) | 26 (23.6) | 39 (36.1) | 49 (45.0) | 0.027 |
| Paternal atopy | 41 (42.3) | 43 (43.9) | 40 (40.0) | 37 (37.0) | 46 (45.1) | 0.949 | 35 (38.0) | 51 (50.5) | 44 (45.4) | 33 (32.0) | 44 (42.3) | 0.484 |
| Median (range) maternal age | 27 (16–38) | 27 (17–40) | 28 (17–38) | 28 (16–41) | 28 (16–39) | 0.002 | 27 (16–41) | 27 (16–39) | 28 (18–38) | 28 (17–37) | 29 (19–40) | 0.009 |
| Median (range) paternal age | 28 (19–44) | 28 (19–52) | 29 (17–44) | 30 (17–53) | 31(18–59) | 0.002 | 28 (19–59) | 28 (17–52) | 29 (18–45) | 29 (19–42) | 30 (20–53) | 0.059 |
| SEC I/II | 29 (28.7) | 26 (26.8) | 28 (27.7) | 27 (27.6) | 35 (36.1) | 0.293 | 24 (26.7) | 24 (25.0) | 26 (26.3) | 32 (31.7) | 40 (37.0) | 0.052 |
| First born | 53 (48.6) | 54 (49.5) | 52 (47.3) | 40 (36.7) | 33 (30.3) | 0.001 | 40 (36.7) | 46 (42.2) | 42 (38.2) | 55 (50.5) | 50 (45.9) | 0.076 |
| Median (range) no of people/room | 0.6 (0.3–1.7) | 0.6 (0.3–1.0) | 0.6 (0.3–1.0) | 0.6 (0.3–1.3) | 0.6 (0.3–1.0) | 0.033 | 0.7 (0.3–1.3) | 0.7 (0.3–1.7) | 0.6 (0.3–1.4) | 0.6 (0.3–1.0) | 0.6 (0.3–1.3) | <0.001 |
| Pet cat by age 1 | 43 (39.5) | 30 (27.5) | 40 (36.4) | 32 (29.4) | 36 (33.0) | 0.440 | 6 (5.5) | 7 (6.4) | 10 (9.1) | 54 (49.5) | 104 (95.4) | <0.001 |
| Pet dog by age 1 | 27 (24.8) | 33 (30.3) | 31 (28.2) | 31 (28.4) | 30 (27.5) | 0.787 | 46 (42.2) | 35 (32.1) | 27 (24.6) | 28 (25.7) | 17 (15.6) | <0.001 |
| Breast feeding | 67 (61.5) | 62 (56.9) | 66 (60.0) | 71 (65.1) | 78 (71.6) | 0.052 | 72 (66.1) | 65 (59.6) | 64 (58.2) | 71 (65.1) | 71 (65.1) | 0.802 |
| Anyone smoking in the home at age 1 | 52 (47.7) | 49 (45.0) | 48 (43.6) | 47 (43.1) | 34 (31.2) | 0.020 | 54 (49.5) | 51 (46.8) | 46 (41.8) | 47 (43.1) | 33 (30.3) | 0.005 |