Table 3.
Difference-in-Differences Model Fitted on Self-Reported Total or Home Secondhand Smoke (SHS) Exposure for Nonsmoking Pregnant Women Living With a Smoking Husband in Sichuan Province, China
| Total secondhand smoke exposure | Secondhand exposure at home | |||
|---|---|---|---|---|
| OR | 95% CI | OR | 95% CI | |
| Constant (no exposure) | 0.55 | 0.27 to 1.11 | 0.88 | 0.42 to 1.82 |
| Constant (15–59min exposure) | 3.27 | 1.64 to 6.52 | 6.99 | 3.36 to 14.52 |
| D i | 0.98 | 0.76 to 1.26 | 0.93 | 0.72 to 1.20 |
| D 1 T i | 0.28 | 0.22 to 0.36 | 0.47 | 0.36 to 0.62 |
| D 2 T i | 0.57 | 0.42 to 0.75 | 0.67 | 0.50 to 0.90 |
| D i × D 1 T i | 0.47 | 0.31 to 0.71 | 0.33 | 0.21 to 0.53 |
| D i × D 1 T i × D 2 T i | 0.98 | 0.63 to 1.55 | 1.56 | 0.95 to 2.56 |
| Age (y) | 1.00 | 0.99 to 1.02 | 1.00 | 0.98 to 1.02 |
| Region | ||||
| Rural | 1.73 | 1.43 to 2.09 | 1.78 | 1.46 to 2.18 |
| Urban | — | — | ||
| Education | ||||
| Middle school or less than middle school | 0.95 | 0.71 to 1.27 | 0.77 | 0.57 to 1.04 |
| High school | 1.22 | 0.92 to 1.61 | 1.04 | 0.78 to 1.41 |
| College or higher | — | — | ||
| Working situation | ||||
| Unemployed | 0.91 | 0.77 to 1.07 | 1.02 | 0.86 to 1.22 |
| Employed | — | — | ||
| Husband’s daily cigarette consumption | ||||
| Under 5 | 0.18 | 0.13 to 0.24 | 0.11 | 0.08 to 0.15 |
| 5–9 | 0.28 | 0.22 to 0.36 | 0.20 | 0.16 to 0.27 |
| 10–14 | 0.43 | 0.33 to 0.55 | 0.46 | 0.35 to 0.59 |
| 15–19 | 0.52 | 0.39 to 0.69 | 0.60 | 0.45 to 0.79 |
| Over 20 | — | — | ||
| Smoking home rules | ||||
| Smoking was allowed in all parts of the home | 4.01 | 3.11 to 5.16 | 4.88 | 3.68 to 6.47 |
| Smoking was allowed in some parts of the home | 2.21 | 1.71 to 2.86 | 1.89 | 1.41 to 2.52 |
| Smoking was not allowed in any part of the home | — | — | ||
| Family net income per month (RMB) | ||||
| Under 999 | 0.84 | 0.66 to 1.07 | 0.87 | 0.68 to 1.11 |
| 1000–2999 | 0.98 | 0.79 to 1.20 | 0.97 | 0.78 to 1.21 |
| Over 3000 | — | — | ||
| Scores of SHS knowledge | 1.00 | 0.99 to 1.02 | 1.00 | 0.99 to 1.02 |
| Attitude | ||||
| Indifferent | 1.93 | 1.46 to 2.57 | 1.77 | 1.33 to 2.26 |
| Dislike | 1.24 | 1.04 to 1.49 | 1.07 | 0.88 to 1.30 |
| Strongly dislike | — | — | ||
CI = confidence interval; OR = odds ratio. D i = dummy variable for group assignment; D 1 T i = dummy variable for time period (0 = baseline survey period, 1 = second and third survey period); D 2 T i = dummy variable for time period (0 = baseline and second survey periods, 1 = third survey period); D i × D 1 T i = effect of the intervention; D i × D 1 T i × D 2 T i = differential effect of the intervention between the second and third survey period.