A joint US-China study concluded that exposure to second-hand smoke increased the risk of osteoporosis in pre-menopausal women by a factor of three. The results of the trial, which were presented at the International Osteoporosis Foundation meeting in Toronto, also suggested that the risk of osteoporosis among men was increased by exposure to cigarette smoke. Research conducted by the Harvard School of Public Health on 14,000 Chinese trial participants found that osteoporosis risk doubled among people who were exposed to the second-hand smoke of one smoker, and tripled when exposed to the secondhand smoke of two or more. As a result, the study found, their risk of breaking a bone other than the spine was 2.6 times higher than that of other women.