Table 2. Distribution of confounding variables between swimming and non-swimming groups.
| Non-swimming at 3y | Swimming at 3y | P value | |||
|---|---|---|---|---|---|
| Number | % | Number | % | ||
| Sex, male | 484 | 49.9 | 69 | 54.8 | 0.309 |
| Birthweight <2500g | 111 | 11.5 | 14 | 11.1 | 0.900 |
| Sibling(s) >0 | 414 | 42.8 | 37 | 29.4 | 0.004a |
| Pet ownership | 171 | 17.7 | 16 | 12.7 | 0.162 |
| Environmental tobacco smoke exposure at 3y | 305 | 31.8 | 35 | 28.2 | 0.423 |
| TV viewing at 3y >3hr on weekends | 76 | 7.9 | 19 | 15.1 | 0.007a |
| Income <4,000,000 yen/year | 91 | 10.1 | 2 | 1.7 | 0.003a |
| Maternal age > = 35 | 406 | 41.9 | 49 | 38.9 | 0.513 |
| Maternal education level, low | 233 | 25.1 | 28 | 23.3 | 0.682 |
| Maternal asthma | 137 | 14.1 | 19 | 15.1 | 0.776 |
| Maternal atopic dermatitis | 138 | 14.2 | 25 | 19.8 | 0.097 |
| Maternal rhinitis | 491 | 50.7 | 62 | 49.2 | 0.757 |
| Maternal asthma, | 565 | 58.3 | 73 | 57.9 | 0.937 |
| atopic dermatitis or rhinitis | |||||
| Breastfeeding before 6m | 155 | 16.3 | 9 | 7.3 | 0.009a |
| BMI Z-score at 3y | 0.15 | 0.89 | 0.10 | 0.85 | 0.555 |
| Ever wheeze at 3y | 235 | 24.3 | 30 | 23.8 | 0.903 |
| Ever rhinitis at 3y | 270 | 28.1 | 29 | 23.0 | 0.227 |
| Current wheeze at 5y | 163 | 16.8 | 16 | 12.7 | 0.237 |
| Current rhinitis at 5y | 346 | 35.7 | 40 | 31.7 | 0.377 |
TV: television, 3y: age 3 years, 5y: age 5 years, 6M: age 6 months
Sex, birthweight, sibling(s), pet ownership, environmental tobacco smoke exposure at 3y, TV viewing at 3y >3h on weekends, income <4,000,000 yen/year, maternal age > = 35, maternal education level, maternal asthma, atopic dermatitis or rhinitis, swimming lessons at 3y, ever wheeze at 3y, ever rhinitis at 3y, current wheeze at 5y, current rhinitis at 5y, and breastfeeding before 6m were analyzed using the ϰ2 test; BMI Z-score at 3y was analyzed using Student’s t test.
aP < 0.05