We hypothesized that each copy of the risk allele carried by the mother would be associated with reduced offspring birth weight, via its association with smoking quantity, in women who smoked during pregnancy.
The ND of probands and other smoker participants was assessed with the three measures commonly used in the tobacco research field: Smoking Quantity (SQ; number of cigarettes smoked per day), the Heaviness of Smoking Index (HSI; 0 6 scale), and the Fagerström Test for Nicotine Dependence score (FTND; 0 10 scale) as a continuous variable.
This allowed us to impute a smoking quantity for current smokers when the quantity smoked was not recorded.
Smoking quantity is a measure of number of cigarettes a respondent smokes on the days he or she smokes.
Smoking quantity was recorded as a categorical variable, with categories; 0 cigarettes smoked per day, 1 9, 10 19, 20 29, 30 39, and 40 or more.
> -wrap-foot> In women who smoked during pregnancy, each additional T-allele, which is associated with greater smoking quantity, was associated with a 0.04 standard deviation (SD) (95% CI: 0.01 0.08 SD) lower birth weight (P = 0.014).
Given the availability of smoking measures in our sample, we also tested if an effect of these variants on smoking quantity (CPD) or nicotine dependence (FTND) was detectable in our sample.
Integrative data analysis, the process of pooling and analyzing data from multiple studies, produces larger and more heterogeneous samples with which to evaluate measurement equivalence across the full continuum of smoking quantity and frequency.
For binge drinking, drinking quantity, smoking quantity, and smoking frequency, the protective effect of 9R/9R diminishes in young adulthood.
The common pattern of lifecourse-gene interaction for binge drinking, drinking quantity, smoking quantity, and smoking frequency can be explained by the legal age for alcohol and smoking.
In the main-effect models, the effect of 9R/9R is either marginally significant (binge drinking, smoking frequency, and seatbelt wearing) or non-significant (smoking quantity).
