Table I.
Description of the study population∗
| Characteristic | All (n = 769) |
Hay fever (n = 99 [12.9%]) |
No hay fever (n = 670 [87.1%]) |
P value |
|---|---|---|---|---|
| n (%)/Total | n (%)/Total | n (%)/Total | ||
| Farm child (yes)† | 367 (47.7)/768 | 31 (31.3)/99 | 336 (50.2)/670 | .0005 |
| Exposure to cats at 2 mo (yes)‡ | 199 (26.0)/767 | 19 (19.2)/99 | 180 (27.0)/668 | .11 |
| Exposure to dogs at 2 mo (yes)‡ | 147 (19.2)/766 | 17 (17.2)/99 | 130 (19.5)/667 | .68 |
| Maternal age at pregnancy (y), mean ± SD | 31.2 ± 4.5 (n = 769) | 31.4 ± 4.4 (n = 99) | 31.2 ± 4.5 (n = 670) | .52 |
| Maternal smoking (yes)§ | 96 (12.5)/766 | 16 (16.5)/97 | 80 (12.0)/669 | .25 |
| Second-hand smoking (yes)‖ | 33 (4.3)/764 | 3 (3.1)/98 | 30 (4.5)/666 | .79 |
| Parental education (yes)¶ | .13 | |||
| Low | 62 (8.1)/764 | 3 (3.1)/97 | 59 (8.9)/667 | |
| Medium | 280 (36.7/764) | 39 (40.2)/97 | 241 (36.1)/667 | |
| High | 422 (56.7)/764 | 55 (56.7)/97 | 367 (55.0)/667 | |
| Use of antibiotics during pregnancy (yes)# | 204 (27.0)/755 | 26 (26.5)/98 | 178 (27.1)/657 | .99 |
| Parental atopy (yes)∗∗ | 416 (54.4)/765 | 72 (73.5)/98 | 344 (51.6)/667 | <.0001 |
| Mode of delivery (normal) | 624 (81.9)/762 | 82 (83.7)/98 | 542 (81.6)/664 | .68 |
| Premature birth (yes)†† | 11 (1.4)/769 | 1 (1.0)/99 | 10 (1.5)/670 | .99 |
| Birth weight (kg), mean ± SD | 3.4 ± 0.44 (n = 605) | 3.4 ± 0.5 (n = 82) | 3.4 ± 0.4 (n = 523) | .81 |
| Breastfeeding 2 mo (yes)‡‡ | 711 (92.7)/767 | 90 (90.9)/99 | 621 (93.0)/668 | .41 |
| Gender (female) | 366 (47.7)/768 | 42 (42.4)/99 | 324 (48.4)/669 | .28 |
| Having siblings (yes) | 494 (64.2)/769 | 60 (60.6)/99 | 434 (64.8)/670 | .43 |
| Use of antibiotics during first y of life (wk), mean ± SD§§ | 0.03 ± 0.3 (n = 746) | 0.01 ± 0.1 (n = 97) | 0.03 ± 0.4 (n = 649) | .86 |
| Doctor‘s diagnosis of hay fever (yes) | 36 (4.7)/769 | 36 (36.4)/99 | NA | NA |
| Inhalant sensitization (IgE ≥ 0.7 kU/L or SPT ≥ 3 mm) at 10.5 y‖‖ | 259 (49.6)/522 | 66 (86.8)/76¶¶ | 193 (43.3)/446¶¶ | <.0001 |
| Concomitants## | ||||
| Asthma (yes) | 69 (9.0)/764 | 28 (28.9)/97 | 41 (6.2)/667 | <.0001 |
| Eczema (yes) | 100 (13.1)/763 | 36 (36.7)/98 | 64 (9.6)/665 | <.0001 |
| Food allergy (yes) | 41 (5.5)/746 | 21 (21.7)/97 | 20 (3.1) /649 | <.0001 |
IgE, Immunoglobulin E; NA, not applicable.
The categorical variables are presented as frequency (percentage) and the continuous variables as mean. The tests for differences between the groups are χ2 or Fischer exact test for categorical variables and Mann-Whitney U test for continuous variables.
Farm child was defined as “Children of mothers living on family-run livestock farms were assigned to the farm group. The nonfarm group included children of mothers from the same rural areas but not living on a farm.
Exposure to pets at 2 mo (cats and dogs) was defined by asking “If you have cats?,” “If you have dogs?,” and “If they stay indoors in the house?”
Maternal smoking during pregnancy was defined using the following questions, “Have you in your life smoked more than 5 packs of cigarettes?” Or “Have you quit smoking in the meantime?” and if yes, “Was it during this pregnancy?” Smoking by father, “Have you in your life smoked more than 5 packs of cigarettes?” Or “Do you still smoke?”
Second-hand smoking “How many cigarettes are on average per day were smoked in your house by other people?” If > 1 then second-hand smoking was defined as 1; else 0.
Parental education was defined as low (<10 y), medium (10 y) and high (>10 y).
Use of antibiotics during pregnancy was defined by asking, “Have you taken antibiotics since the beginning of pregnancy?” Or “Have you taken any antibiotics during this pregnancy?”
Parental atopy was defined as doctor’s diagnosis of hay fever, atopic dermatitis, or asthma ever in mother or father.
Child was defined as premature if the child was born before the completion of 37 wk of pregnancy.
Breastfeeding at 2 months (yes or no) was defined by asking, “If you have ever breastfed?”
Use of antibiotics by a child during the first year of life was defined as, “Total no. of weeks with antibiotics ingested.”
Inhalant sensitization was defined as at least 1 IgE specific to alder, birch, hazel, plantain, mugwort, alternaria, grass, rye, Dermatophagoides pteronyssinus, D, farina, cat, dog, or horse at levels ≥ 0.7I UmL–1 or SPT (birch, grass, alternaria, D. pteronyssinus, D. farinae, cat, or dog) ≥ 3mm. Serum-specific IgE and SPT was not measured in the Austrian study center; hence, only subsample n = 522 was included.
Asthma was defined as a physician’s diagnosis of asthma or recurrent obstructive bronchitis established until 10.5 y. Eczema and food allergy were defined as physician diagnoses at least once until 10.5 y.