Objective. Increasing evidence has suggested an association between sleep duration and osteoporosis risk, although the results of previous studies have been inconsistent. To our knowledge, this is the first meta-analysis of the literature and quantitative estimates of the association between sleep duration and risk of osteoporosis in population-based studies of middle aged and elderly women. Methods. Pertinent studies were identified by searching PubMed and EMBASE databases up to February 2016. Five out of six included studies were cross-sectional and one was a prospective cohort study. They included 72,326 participants from three different countries. We extracted 31,625 individuals in these studies for our meta-analysis. Results. A pooled odds ratio analysis in women between 40 to 86 years indicated that there is an inverse relationship between sleep duration and osteoporosis (overall OR =1.07 95% CI: 1.00-1.15). The negative association of long sleep duration (8 h or more per day) with osteoporosis risk was observed in middle aged and elderly women (OR =1.22, 95% CI: 1.06-1.38) but not in women with short sleep duration (7 h or less per day) (OR =0.98, 95% CI: 0.90-1.05). Conclusion. This meta-analysis suggests that long sleep duration (8 h or more per day) may be associated with a higher risk of osteoporosis in middle-aged and elderly. Further prospective cohort studies with longer follow-up periods, valid instruments for measurement of sleep duration and dynamic sleep quality are warranted to support the possible relationship between sleep duration and osteoporosis risk in women. (C) 2017 Elsevier Inc. All rights reserved.