Age of initiation and switching patterns between smokeless tobacco and cigarettes among college students in the United States.

A stratified, random, multi-stage, cluster sample of physical activity classes among 72 colleges and universities throughout the United States yielded 5,894 usable responses (males = 2,888); (females = 3,006). Twenty-three per cent of the students who began smoking before the age of 10 were current smokers, while 61 per cent of those who began using smokeless tobacco before the age of 10 were current smokeless tobacco users. College students were more likely to switch from smokeless tobacco to cigarettes than from smoking cigarettes to smokeless tobacco.