Characteristics of the study populations
| 1992/3 | 1993/4 | 1994/5 | 1996/7 | 1998/9 | 2000/1 | |
|---|---|---|---|---|---|---|
| *All children with known sex, age and residence for at least two years in study area. | ||||||
| †Proportion of children participating in blood sampling of those invited to participate (these were random subsamples after 1995). | ||||||
| ‡High socioeconomic status (SES) defined as mother, father, or both having at least 13 years of school education. | ||||||
| ¶Environmental tobacco smoke (ETS) defined as any passive smoke exposure in the home. | ||||||
| §Exclusive breast feeding for at least 4 months. | ||||||
| Addressed | 1410 | 1309 | 1402 | 1513 | 1500 | 1548 |
| Questionnaires completed | 1077 | 1079 | 1078 | 1171 | 1197 | 1160 |
| Participation rate | 76.4% | 82.4% | 76.9% | 77.3% | 79.8% | 74.9% |
| Study sample* | 919 | 955 | 930 | 1030 | 1036 | 1070 |
| Serum samples | 798 | 763 | 832 | 674 | 722 | 653 |
| Participation in blood sampling† | 86.8% | 79.9% | 89.5% | 78.4% | 82.4% | 93.4% |
| Mean (SD) age (years) | 10.4 (0.6) | 10.3 (0.6) | 10.3 (0.6) | 10.2 (0.6) | 10.2 (0.6) | 10.2 (0.5) |
| Sex (female) | 467 (51%) | 474 (50%) | 450 (48%) | 524 (51%) | 519 (50%) | 503 (47%) |
| German nationality | 761 (83%) | 731 (77%) | 670 (72%) | 717 (70%) | 739 (71%) | 772 (72%) |
| German children only | ||||||
| SES high‡ | 145 (19%) | 196 (27%) | 145 (22%) | 170 (24%) | 194 (26%) | 212 (27%) |
| ETS¶ | 405 (53%) | 360 (49%) | 348 (52%) | 360 (50%) | 366 (50%) | 388 (50%) |
| No of siblings | ||||||
| ⩾2 | 297 (39%) | 264 (36%) | 251 (37%) | 263 (37%) | 278 (38%) | 298 (39%) |
| Familial history of asthma, atopic eczema or hay fever | 221 (29%) | 243 (33%) | 239 (36%) | 241 (34%) | 269 (36%) | 283 (37%) |
| Breast feeding§ | 158 (21%) | 149 (20%) | 174 (26%) | 220 (31%) | 246 (33%) | 255 (33%) |