Table 2.
Univariable Analysis of Child Cotinine Levels at 7 and 15 Years for Nonsmokers and a Univariable Analysis of Child Smoking With Child Cotinine Levels at 15
| Predictor | 7 Years | 15 Years | ||||||
|---|---|---|---|---|---|---|---|---|
| n | Ratio of geometric means | 95% CI | p value | n | Ratio of geometric means | 95% CI | p value | |
| Child sex | ||||||||
| Male | 2,904 | – | – | – | 1,574 | – | – | – |
| Female | 2,737 | 1.09 | 0.96, 1.26 | .186 | 1,628 | 0.73 | 0.59, 0.91 | .005 |
| Housing tenure | ||||||||
| Owned | 4,477 | – | – | – | 1,800 | – | – | – |
| Private rent | 159 | 1.60 | 1.07, 2.41 | .023 | 67 | 1.32 | 0.62, 2.80 | .471 |
| Subsidized rent | 487 | 3.56 | 2.80, 4.53 | <.001 | 128 | 2.58 | 1.49, 4.53 | .001 |
| Crowding Index | ||||||||
| <1 | 384 | – | – | – | 150 | – | – | – |
| 1– 1.5 | 2,250 | 0.48 | 0.36, 0.63 | <.001 | 1,075 | 0.65 | 0.38, 1.09 | .105 |
| >1.5 | 2,000 | 0.40 | 0.30, 0.53 | <.001 | 918 | 0.90 | 0.53, 1.54 | .705 |
| Maternal education | ||||||||
| Up to 16 years | 3,093 | – | – | – | 1,741 | – | – | – |
| 18+ years | 1,573 | 0.59 | 0.50, 0.68 | <.001 | 1,103 | 0.64 | 0.51, 0.81 | <.001 |
| Number of siblings | ||||||||
| 0 | 1,724 | – | – | – | 1,007 | – | – | – |
| 1 | 1,776 | 1.07 | 0.90, 1.27 | .439 | 765 | 1.03 | 0.77, 1.38 | .848 |
| 2 | 967 | 1.20 | 0.98, 1.46 | .086 | 243 | 0.58 | 0.38, 0.89 | .012 |
| 3 | 473 | 1.45 | 1.12, 1.90 | .005 | 68 | 1.17 | 0.55, 2.48 | .683 |
| 4+ | 595 | 1.32 | 1.04, 1.68 | .022 | 60 | 2.03 | 0.90, 4.53 | .084 |
| Mother smokes | ||||||||
| 0 | 3,341 | – | – | – | 2,301 | – | – | – |
| <10 | 273 | 1.95 | 1.43, 2.69 | <.001 | 156 | 1.73 | 1.05, 2.86 | .031 |
| 10+ | 431 | 5.10 | 3.94, 6.55 | <.001 | 230 | 5.10 | 3.35, 7.69 | <.001 |
| Child smokes | ||||||||
| No | – | – | – | – | 2,827 | – | – | – |
| Nonweekly | – | – | – | – | 395 | 2.30 | 2.14, 2.46 | <.001 |
| Weekly | – | – | – | – | 219 | 33.78 | 30.88, 37.34 | <.001 |
Note. CI = confidence interval.
Predictors comprised child sex, housing tenure (owned/mortgaged, privately rented, subsidized housing rented from council/housing association), maternal education, crowding index (ratio of number of residents to number of rooms in house), maternal education (education up to 16 years and education up to 18 years or older), parity (whether study child is first/second/third child or greater), and mother’s smoking status (does not smoke, smokes fewer than 10 cigarettes/day, smokes 10 or more cigarettes/day). All univariable analyses use cotinine levels within nonsmoking children, except the child smoking model, which includes smoking and nonsmoking participants.