Table 2. Cigarette smoking among students of Tehran Medical University during the study period .

Cigarette use	2006	2007	2008	2009
	N=1761	N=1741	N=1755	N=1568
Lifetime prevalence of smoking cigarette even one puff1	25.7%	) 25.3%	9.6%	19.6%
Lifetime prevalence of smoking at least one complete cigarette	16.9%	17.6%	14.3%	13.3%
Twelve months prevalence of smoking at least one complete cigarette	12.5%	13.2%	10.8%	10.1%
Last month prevalence of cigarette	8.2%	7.8%	6.1%	5.8%
Last week prevalence of cigarette	4.8%	5.2%	3.8%	3.2%
Prevalence of daily cigarette use	3.4%	4.0%	2.9%	1.8%
Age of first cigarette use (at least one complete cigarette)
Mean (±SD)	17.3 (±3.4)	16.9 (±3.5)	16.4 (±3.7)	16.2 (±3.9)
Median	18	18	17	17
Mode	18	18	19	20
Number of cigarette used per day*
Mean (±SD)	9.2 (±7.2)	10.9 (±9.4)	12.4 (±7.2)	9.4 (±7.8)
Median	7	7	10	6
Mode	5	5	20	5

*Among daily smokers