Context: Sleep deprivation has detrimental metabolic consequences. Osteopenia and sarcopenia usually occur together and increase risk of fractures and disease. Results from studies linking sleep parameters to osteopenia or sarcopenia are scarce and inconsistent. Objective: To examine the associations of sleep parameters with osteopenia and sarcopenia, considering the influence of sex and menopause. Design, setting and participants: Cross-sectional analysis of 915 participants (45-65 years, 56% women, BMI 26 (range: 18-56) kg/m2) in the Netherlands Epidemiology of Obesity (NEO) study, a population-based cohort study. Sleep duration, quality, and timing were assessed with the Pittsburgh Sleep Quality Index (PSQI); bone mineral density and relative appendicular muscle mass were measured by DXA scans. Linear and logistic regressions were performed to associate sleep parameters to bone mineral density, relative appendicular muscle mass, osteopenia (t-score between -1 and -2.5) and sarcopenia (1 SD below average muscle mass). Results: After adjustment for confounding factors, one unit increase in PSQI score (OR and 95% CI, 1.09,1.03-1.14), declined self-rated sleep quality (1.76,1.03-3.01), sleep latency (1.18, 1.06-1.31), and a one hour later sleep timing (1.51,1.08-2.11), but not sleep duration (1.05, 0.90-1.23), were associated with osteopenia. PSQI score (1.10, 1.02-1.19) was also associated with sarcopenia; OR's of sleep latency and later mid-sleep time with sarcopenia were 1.14 (0.99-1.31) and 1.54 (0.91-2.61), respectively. Associations were somewhat stronger in women and varied per menopausal status. Conclusions: These results suggest that decreased sleep quality and a later sleep timing are risk factors for osteopenia and sarcopenia in middle aged individuals.