SMOKING AS A RISK FACTOR FOR OSTEOPOROSIS - FACT OR FICTION

To evaluate smoking as a risk factor for osteoporosis, we performed a qualitative analysis of 40 international studies investigating statistical associations between smoking and osteoporosis related end-points. Using standardized causality assessment criteria, we failed to demonstrate a relationship between smoking and osteoporosis. Because such a relationship is biologically plausible, we then undertook a quantitative metaanalysis of 8 epidemiological hip fracture studies. Relative risk, estimated as the << combined odds ratio >>, was 1.33 (95 % confidence interval 1.14-1.54) in the case-control studies and 1.63 (95 % confidence interval 1.27-2.09) in the prospective studies. These data suggest that smoking is a modest risk factor for osteoporosis. However, studies of effects of smoking on peak bone mass would be of interest in view of the prevalence shift of smoking towards increasingly young age groups. Early exposure to smoke may decrease peak bone mass. Furthermore, Kiel recently found evidence that replacement hormone therapy may be ineffective in preventing hip fractures in postmenopausal women who smoke. Reducing smoking is an important goal for the primary and secondary prevention of osteoporosis in teenagers and postmenopausal women, respectively.