LAUSR

We would like to thank Dr. Cerit for his interest in our paper describing a potential association of atrial fibrillation and subsequent hip fracture [1]. As pointed out, vitamin K antagonists interfere with the gamma-carboxylation of glutamic acid residues and inhibits the activation of bone matrix proteins [2]. In this context, several studies have described a possible association of warfarin use with an increased risk of osteoporotic fracture, albeit this has not been seen in other analyses [3–5]. Although oral anticoagulation use in our study was associated with incident hip fracture in men but not women, the addition of this variable to the final Cox proportional hazards regression models did notmaterially alter the associations observed between atrial fibrillation and hip fracture in men (HR 1.54, 95% CI 1.23–1.92) or women (HR 2.14, 95% CI 1.85–2.47). We were not able to differentiate anticoagulation with warfarin as opposed to non-vitamin K anticoagulants, but it is likely that use of the latter was uncommon during the time period of this analysis.