Table 2.

Smoking variable definitions

Smoking variables	Category/unit	Definition
Current smoking status	Current, former or never	Is patient currently smoking, not currently smoking but did smoke at least 100 cigarettes, or not smoked 100 cigarettes in lifetime?
Amount smoked	<1 pack/day, 1 pack/day, >1 pack/day	The largest number of cigarettes smoked each day for at least 2 weeks for both current and former smokers
Age at smoking initiation	≤16, 17–21, ≥22	Age at which both current and former smokers began to smoke cigarettes
Years since smoking cessation	≤5 years ago, >5 years ago	The number of years since the patient quit smoking
Past second-hand smoke (SHS) exposure (Period #3 only)	Yes, no	When living at home with parents, did they smoke inside the home?
Current second-hand smoke (SHS) hours (Period #3 only)	None, 0.5–2.5 h/day, 3 or more h/day	Number of hours exposed to smoke from another person’s cigarettes at (1) home, (2) work or (3) other