Table 3.
Multivariable generalized estimating equation logistic regression model* for current smoking status (yes vs no) at study years 1, 2, and 3 after baseline for baseline current smokers (n = 14621)
| Predictor variables | Odds ratio (95% CI) P |
|---|---|
| Age, per 1 y | 0.949 (0.941 to 0.959) <.001 |
| Race/ethnicity† | |
| White | Referent group |
| Black | 1.028 (0.867 to 1.218) .75 |
| Asian | 1.109 (0.845 to 1.455) .46 |
| American/Alaskan Native | 0.943 (0.555 to 1.602) .83 |
| Hawaiian native/Pacific Islander | 1.172 (0.679 to 2.021) .57 |
| Mixed race | 1.218 (0.922 to 1.611) .17 |
| Refused/unknown | 0.357 (0.219 to 0.582) <.001 |
| Education, per 1 unit increase in 6 possible levels‡ | 0.976 (0.953 to 1.000) .051 |
| Marital status, without partner vs with | 1.261 (1.169 to 1.360) <.001 |
| Body mass index,* kg/m2, assessed with 3 RCSplines | NA§ |
| Smoking intensity, cigarettes/d | 1.010 (1.006 to 1.014) <.001 |
| Smoking duration, y | 1.028 (1.020 to 1.035) <.001 |
| Secondhand smoke exposure at home, yes vs no | 1.132 (1.018 to 1.259) .02 |
| Pipe smoking, past or current regular user, yes vs no | 0.830 (0.756 to 0.912) <.001 |
| Cigar smoking, past or current regular user, yes vs no | 0.740 (0.670 to 0.817) <.001 |
| Screening result, lagged 1 year║ | |
| Normal | Referent group |
| Minor abnormality, not suspicious for lung cancer | 0.914 (0.859 to 0.974) .005 |
| Major abnormality, not suspicious for lung cancer | 0.811 (0.722 to 0.912) <.001 |
| Positive, suspicious for lung cancer but stable from previous screen | 0.785 (0.706 to 0.872) <.001 |
| Positive, suspicious for lung cancer, new or changed from previous screen | 0.663 (0.607 to 0.724) <.001 |
| Model constant, unexponentiated | 4.794325 |
* This model is additionally adjusted for study year, study center, and randomization arm. CI = confidence interval; NA = not applicable; RCSplines = restricted cubic splines.
† The likelihood ratio test evaluating nested models with and without race/ethnicity had a P value of .04.
‡ Education levels are less than high school completed, high school completed, some post–high school, associate degree or some college, bachelor degree, and graduate or professional degree.
§ The exponentiated beta coefficients are not directly interpretable as odds ratios so are not presented here. The likelihood ratio tests P value for nested models including and excluding the three restricted cubic splines was .0003. The P value testing the nonlinearity of body mass index was .003. The knot locations for the body mass index splines were at 20.02, 25.74, 29.05, and 37.12. The beta coefficients for body mass index restricted cubic splines 1, 2, and 3 were −0.0472887, 0.1661889, and −0.5223123, respectively.
║ To ensure a correct temporal sequence the previous years screening result was used to predict smoking behavior as reported in the annual summary update.