Chunk #18 — RESULTS — Predicting Use of Alcohol, Cigarettes, and Cannabis with CSA History: Results of Cox Proportional Hazards Regression Analyses — Cigarettes
As seen in Table 4, in Model 1, CSA was associated with a significant increase in risk for cigarette use through age 19. The highest HR was observed for the period of risk from ages 4–9 (2.61; CI:1.79–3.80), but the decrease in HR estimates across periods of risk was more gradual than for alcohol; point estimates of 1.94 and 1.40 were found for ages 10–14 and 15–19, respectively. The addition of co-twin early use and its interaction with zygosity led to a significant drop in HRs for ages 4–9 and 10–14, but CSA remained a significant predictor of cigarette use (HR=1.70; CI: 1.13–2.56 for 4–9, HR=1.34; CI: 1.12–1.59 for 10–14). The HR for ages 15–19 in Model 2 was nearly identical to that for ages 10–14 and was not significantly lower than in Model 1. Co-twin early cigarette use was associated with a greater than 6-fold increase in risk for use at ages 4–9, and over two and a half fold increase for ages 10–14. Genetic influences were evident at ages 10–14 (HR for co-twin use by zygosity was 2.14, CI=1.60–2.86).
