Table 3.
Hazard ratios for incident rheumatoid arthritis, overall and by serologic phenotype, according to childhood parental smoking at home among women in the Nurses’ Health Study II (n=90,923).
| RA cases/Person-years | Base model* | +Confounders** | +Adult personal smoking and covariates (conventional)† | Controlled direct effect‡ | |
|---|---|---|---|---|---|
| All RA | |||||
| No parent smoked | 160/829,934 | 1.00 (ref) | 1.00 (ref) | 1.00 (ref) | 1.00 (ref) |
| Any parent smoked | 372/1,510,400 | 1.24 (1.03, 1.49) | 1.18 (0.96, 1.46) | 1.11 (0.90, 1.38) | 1.27 (0.84, 1.92) |
| Seropositive RA | |||||
| No parent smoked | 95/829,037 | 1.00 (ref) | 1.00 (ref) | 1.00 (ref) | 1.00 (ref) |
| Any parent smoked | 257/1,508,631 | 1.46 (1.15, 1.84) | 1.41 (1.08, 1.83) | 1.30 (0.99, 1.70) | 1.75 (1.03, 2.98) |
| Seronegative RA | |||||
| No parent smoked | 65/828,417 | 1.00 (ref) | 1.00 (ref) | 1.00 (ref) | 1.00 (ref) |
| Any parent smoked | 115/1,506,166 | 0.93 (0.68, 1.26) | 0.86 (0.60, 1.22) | 0.85 (0.60, 1.21) | 0.77 (0.40, 1.45) |
Adjusted for age and questionnaire cycle.
Additionally adjusted for race/ethnicity, maternal and paternal education, maternal and paternal occupations, home ownership, state born, family history of RA, birthweight, preterm birth, breastfeeding, and maternal smoking during pregnancy (temporally preceding confounders for the childhood parental smoking exposure).
Additionally adjusted for adult personal smoking pack-years and adult passive smoking (years lived with a smoker since age 18) and their preceding covariates (birthweight, preterm birth, breastfeeding, age at menarche, body mass index at age 18, menopausal status and hormone use, parity/breastfeeding, body mass index, physical activity, alternate healthy eating index, residence, and census income).
Controlling for adult personal smoking pack-years and adult passive smoking (years lived with a smoker since age 18) via conditioning and inverse probability weighting using their temporally preceding covariates (birthweight, preterm birth, breastfeeding, age at menarche, body mass index at age 18, menopausal status and hormone use, parity/breastfeeding, body mass index, physical activity (≥ 3 metabolic equivalent), alternate healthy eating index, residence, and census income).