Swanson CM, Blatchford PJ, Orwoll ES, et al. - The Study of Osteoporotic Fractures, ancillary sleep study, was employed to ascertain the relationship between sleep duration and BMD at the total hip and femoral neck in postmenopausal women ≥ 75 years old. In women with actigraphically evaluated shorter sleep duration in unadjusted models only, total hip BMD was higher. According to nocturnal sleep duration following adjusting for BMI in dichotomized (N = 874) or continuous (N = 1,624) sleep duration models or when subjective sleep duration was used, no clinically or statistically important differences in total hip or femoral neck BMD were seen. Longer sleep duration was related to lower total hip BMD when sleep duration involved daytime naps. Therefore, in elderly postmenopausal women, whether evaluated objectively (actigraphy) or subjectively (questionnaire), nocturnal sleep duration was not independently correlated with BMD.