In undertaking this project, we faced numerous challenges. First, smoking behavior differs substantially across populations. Smoking quantity distributions differ across populations; smokers of European ancestry smoke more heavily than do Asians or African Americans. As a result, we decided to compare heavy (>20 cigarettes per day) versus light smoking (≤10 cigarettes per day) in our primary association analysis to more closely capture the contrast between nicotine dependent smokers and non-dependent smokers. We then confirmed the consistency of results using the full distribution of smoking quantity in subsequent analyses.
