Adjusted prevalence of asthma and rhinitis symptoms (parental reports) in three consecutive surveys, stratified by family history of asthma or hay fever
| Study sample/health outcome | 1992–1993 | 1995–1997 | 1999–2000 | p‐value for trend |
| Positive family history of asthma or hay fever n | 432 | 602 | 494 | |
| Wheeze ever | 33.2 (27.8–39.1) | 32.9 (28.1–38.0) | 33.7 (30.4–41.2) | 0.52 |
| Wheeze past year | 9.9 (6.7–14.1) | 9.7 (7.1–13.1) | 5.0 (3.2–7.6) | 0.02 |
| Wheeze after exercise | 9.9 (7.0–13.8) | 10.4 (7.8–13.8) | 9.4 (6.7–13.1) | 0.80 |
| Asthma ever | 15.8 (11.9–20.6) | 16.5 (12.9–20.7) | 12.0 (8.9–15.8) | 0.15 |
| Sneezing attack without cold and itchy watery eyes last year | 21.2 (16.8–26.3) | 19.8 (16.0–24.1) | 23.4 (18.9–28.4) | 0.26 |
| Hay fever | 31.0 (25.8–36.5) | 30.6 (26.1–35.5) | 32.0 (27.0–37.3) | 0.88 |
| Negative family history of asthma or hay fever n | 892 | 1066 | 756 | |
| Wheeze ever | 15.6 (13.2–18.2) | 15.4 (13.2–17.7) | 18.8 (16.0–21.8) | 0.13 |
| Wheeze past year | 3.4 (2.4–4.8) | 3.4 (2.5–4.7) | 3.9 (2.7–5.5) | 0.58 |
| Wheeze after exercise | 6.9 (5.4–8.8) | 5.6 (4.4–7.1) | 6.8 (5.1–8.8) | 0.92 |
| Asthma ever | 5.6 (4.3–7.4) | 5.6 (4.3–7.1) | 6.6 (5.1–8.7) | 0.37 |
| Sneezing attack without cold and itchy watery eyes last year | 10.6 (8.7–12.9) | 7.6 (6.2–9.4) | 7.9 (6.1–10.0) | 0.06 |
| Hay fever | 12.4 (10.3–14.7) | 9.6 (7.9–11.4) | 12.2 (10.0–14.7) | 0.94 |
Data are presented as % (95% confidence interval) unless otherwise stated
Symptom rates were adjusted for study year, sex, parental education, study area, breastfeeding, number of siblings, heating system, carpets in student's bedroom, pet ownership, getting rid of carpets because of the child's allergy, students active smoking, mother filling in the questionnaire and parental perception of air pollution as a risk factor for their child's respiratory health