Lack of utility of cigarettes per day cutoffs for clinical and laboratory smoking research.

BACKGROUND: Most clinical and laboratory smoking research studies require that participants smoke at a certain level to be eligible for enrollment. However, there is limited evidence that use of these cutoffs differentiates groups of smokers along clinically meaningful criteria.
METHODS: Using receiver operating characteristic curves, we analyzed data from daily smokers in the National Epidemiologic Study of Alcohol Use and Related Conditions - III (NESARC-III) to examine the utility of smoking rates for determining whether participants met DSM-5 criteria for tobacco use disorder, experienced nicotine withdrawal or had a history of failed quit attempts. We also examined whether relationships between these variables differed as a function of key sample characteristics.
RESULTS: Smoking rate exhibited a weak relationship with the presence of tobacco use disorder (AUC = 0.664), whether individuals experience nicotine withdrawal (AUC = 0.672) and whether individuals had a history of failed quit attempts (AUC = 0.578). The relationship between smoking rate and a history of failed quit attempts was weaker for women than men (p < .05). Otherwise, utility did not differ as a function of sex, race/ethnicity, education, income, or use of multiple tobacco products. Optimal cutoffs varied somewhat across indices, but the largest number of correct classifications occurred at very low smoking rates.
CONCLUSIONS: Researchers should consider abandoning the use of smoking rate cutoffs to determine study eligibility. If smoking rate cutoffs are used, a rationale should be presented along with justification for the specific cutoff chosen.