Association of the grandmother's and the mother's smoking during pregnancy with asthma development in the grandchild
| Outcome | Exposure | n, total | n, cases | Crude RR (95% CI) | Adj. RR (95% CI)* |
|---|---|---|---|---|---|
| Asthma at 36 months (N=53 169) | Mother and grandmother smoking during pregnancy | ||||
| Neither | 32 701 | 1735 | 1 | 1 | |
| Only grandmother | 10 411 | 686 | 1.24 (1.14 to 1.35) | 1.15 (1.06 to 1.26) | |
| Only mother | 1728 | 106 | 1.15 (0.94 to 1.41) | 1.06 (0.87 to 1.30) | |
| Both grandmother and mother | 1685 | 117 | 1.32 (1.10 to 1.59) | 1.15 (0.95 to 1.40) | |
| Asthma at 7 years (N=25 394) | Mother and grandmother smoking during pregnancy | ||||
| Neither | 15 426 | 708 | 1 | 1 | |
| Only grandmother | 4973 | 299 | 1.32 (1.16 to 1.50) | 1.23 (1.08 to 1.40) | |
| Only mother | 858 | 49 | 1.30 (1.00 to 1.70) | 1.17 (0.89 to 1.53) | |
| Both grandmother and mother | 775 | 49 | 1.42 (1.09 to 1.87) | 1.22 (0.92 to 1.60) | |
| Use of asthma medications at 7 years based on prescription registry (N=45 607) | Mother and grandmother smoking during pregnancy | ||||
| Neither | 26 600 | 1157 | 1 | 1 | |
| Only grandmother | 9172 | 483 | 1.22 (1.10 to 1.35) | 1.14 (1.03 to 1.26) | |
| Only mother | 2180 | 122 | 1.27 (1.06 to 1.53) | 1.11 (0.92 to 1.34) | |
| Both grandmother and mother | 2181 | 143 | 1.49 (1.26 to 1.76) | 1.25 (1.05 to 1.49) | |
Adjusted for maternal age, maternal parity, maternal education, maternal salary, maternal pre-pregnancy BMI, and maternal asthma.
Multiple imputation of missing covariate information by chained equations conducted for all measures of association presented.
*Values for the respondents reporting ‘don't know’ to the grandmother's smoking when pregnant with the mother were imputed using multiple imputation together with all other missing covariate information. There were a total of 6097 children in the analysis of asthma at 36 months, 2884 children in the analysis of asthma at 7 years and 5474 children in the analysis of use of asthma medication in the prescription database for whom we imputed missing information on the combined exposure of both grandmother and mother smoking during pregnancy.