Table 2.

Table 2a. Examples of possible smoking-related questions
Study (N)	Smoking-related questions	Possible responses
Study 1 (2,500)	1. Do you currently smoke cigarettes?	Y/N
	2. If yes, how many cigarettes per day?	###
Study 2 (1,200)	1. Have you smoked more than 100 cigarettes in your lifetime?	Y/N
	2. If yes, do you currently smoke?	Y/N
	3. If yes, how many packs per day do you smoke?	##
Study 3 (8,500)	1. Have you ever smoked?	Y/N
Study 4 (1,250)	1. Do you currently smoke?	Y/N
Study 5 (4,200)	1. Do you smoke?	Y/N
	2. When did you first start smoking regularly?	Past year; 1-5 years ago; >5 years ago
Study 6 (6,600)	1. Have you smoked tobacco in the past month?	Y/N
Study 7 (800)	1. Have you ever smoked regularly?	Y/N
	2. If yes, do you still smoke?	Y/N
	3. If yes, how much do you smoke a day?	1-10 cigarettes, 11-20 cigarettes, 21-30 cigarettes, >30 cigarettes

Table 2b. Examples of possible new variables for cross-study analyses
New variable	Studies that could contribute data	Total N	Comment
Cigarettes per day	Study 1	2,500	Data from Study 7 might also be included if specific values were assigned to each response category, e.g. 5 for category ‘1-10 cigarettes’, 15 for category ‘11-20 cigarettes’, and so on
Packs per day	Study 1 (if convert cigarettes/day to packs/day)	4,500
	Study 2
	Study 7 (if convert categories to packs/day)
Former smoker	Study 2	2,000
	Study 7
Ever smoker	Study 2	10,500	Requires ability to determine if subjects are former smokers
	Study 3
	Study 7
Current smoker	Study 1	16,550
	Study 2
	Study 4
	Study 5
	Study 6 (if current smoker is defined as having smoked in the past month)
	Study 7