Table 3.
Multivariable Analysis of Maternal Smoking on Child Cotinine Levels at 7 and 15 Years for Nonsmokers, and a Multivariable Analysis of Child Smoking on Child Cotinine Levels at 15 on All Individuals
| Predictor | 7 Years (n = 3,128) | 15 Years | ||||
|---|---|---|---|---|---|---|
| Ratio of geometric means | 95% CI | p value | Ratio of geometric means | 95% CI | p value | |
| Mother smokes | ||||||
| 0 | – | – | – | – | – | – |
| <10 | 1.58 | 1.08, 2.32 | .017 | 1.68 | 0.84, 2.89 | .106 |
| 10+ | 3.94 | 2.86, 5.42 | <.001 | 5.26 | 3.06, 9.03 | <.001 |
| Child smokes | ||||||
| No | – | – | – | – | – | – |
| Nonweekly | – | – | – | 1.90 | 1.75, 2.05 | <.001 |
| Weekly | – | – | – | 27.11 | 24.05, 30.57 | <.001 |
Note. CI = confidence interval.
Covariates included in the model 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). The mother smoking model included individuals below the cutoff for active smoking (9.5ng/ml serum) and who self-report as nonsmokers (for 15 only). The child smoking model included all individuals; in addition, the model for child smoking included the mother’s smoking status. Maternal smoking at 15 years old, N =1,868; child smoking at 15 years, N = 2,015.