Fracture risk associated with smoking: a meta-analysis

Objectives. To assess fracture risk associated with smoking. Design. Systematic review. Data sources. Cohort, case-control, and cross-sectional studies identified by searching PubMed and EMBASE, and by recursive screening of reference lists. Subjects. Fifty studies including 512 399 subjects were included. Main outcome measure. Fracture occurrence in current, previous, and never smokers. Results. Fracture risk was significantly increased in current smokers for all fracture types combined (pooled relative risk 1.26, 95% CI 1.12-1.42) and for hip (1.39, 95% CI 1.23-1.58) and spine fractures (1.76, 95% CI 1.10-2.82), but not for wrist fractures (0.86, 95% CI 0.46-1.60). In previous smokers the estimate was significantly lower for as well all types of fractures (1.02, 95% CI 0.85-1.22, P = 0.03 compared with current smokers), as for hip fractures (1.19, 95% CI 1.06-1.34, P = 0.04). There was a trend towards higher risk estimates in previous smokers for hip fractures in case-control studies than in cohort studies. A similar difference between case-control and cohort studies was not present for current smokers. There was a geographical heterogeneity: the risk of hip fractures associated with current smoking increased with latitude, i.e. the risk was higher in Northern Europe and the USA than in Southern Europe and countries close to the equator. Conclusions. Smoking is associated with an increased overall fracture risk, an increased risk of hip and spine but not wrist fractures. Cessation of smoking seems associated with a decrease in fracture risk. The impact of smoking varied geographically with an increase with latitude.