In this study, the levels of ND for smokers were ascertained by three commonly-used measures in the literature: smoking quantity (SQ: defined as the number of cigarettes smoked per day), the Heaviness of Smoking Index (HSI: 0–6 scale), and the Fagerström Test for ND (FTND: 0–10 scale). Given the overlap in the content of these three ND measures, there exists fairly robust correlations among them in the AA (r = 0.88–0.97), EA (r = 0.91–0.97) and pooled (r = 0.89–0.97) samples.
