Comparison of nicotine dependence indicators in predicting quitting among pregnant smokers

Research in the general population of smokers indicates that across various measures of nicotine dependence, time to first cigarette (TTFC) is the strongest single-item predictor of quitting success. Whether those findings generalize to pregnant smokers is unclear. To investigate this matter, we compared TTFC with cigarettes per day (CPD) and the Heaviness of Smoking Index (HSI; Kozlowski, Porter, Orleans, Pope, & Heatherton, 1994) in predicting late-pregnancy abstinence among 289 pregnant women enrolled in 4 smoking-cessation trials assessing the efficacy of financial incentives. Logistic regression was used to compare predictors, with model fit measured using the c statistic (range = 0.5, poor prediction to 1.0, perfect prediction). In simple regressions, model fit was comparable across the 3 measures although strongest for CPD alone (c = 0.70, 0.68, 0.66 for CPD, HSI, and TTFC, respectively). In a stepwise multiple regression, treatment was entered first (c = 0.67), then CPD (c = 0.77), quit attempts prepregnancy (c = .81), TTFC (c = .82), and quit attempts during pregnancy (c = .83). We saw no evidence supporting TTFC as the optimal predictor of quitting among pregnant smokers. Instead, the evidence supported using CPD and TTFC together or CPD alone if using only a single predictor.