['The aim of the present study was to investigate the impact of sleep on osteoporosis.', 'The study used a baseline examination of the Hiroshima Sleep and Healthcare study, which was a cross-sectional and cohort study that addressed the association of sleep habits with lifestyle-related diseases. A total of 1032 participants (25-85 years of age) who underwent health examinations were included. Sleep habits, including its timing (bed time), quantity (time in bed [TIB]), and quality, were assessed using the Pittsburgh Sleep Quality Index (PSQI). The bone stiffness index (SI), a marker of osteoporosis, was measured using quantitative ultrasound systems.', 'Bed time (r\u2009=\u20090.065, p\u2009<0.05), TIB (r\u2009=\u2009-0.064, p\u2009<0.05), and global PSQI score (r\u2009=\u2009-0.126, p\u2009<0.0001) significantly correlated with SI. Multiple regression analyses revealed that after adjusting for age, sex, body mass index, smoking, and alcohol intake, the global PSQI score (β\u2009=\u2009-0.053, p\u2009<0.05) was significantly associated with SI, whereas bed time or TIB was not. Among each component of PSQI, sleep disturbances (β\u2009=\u2009-0.084, p\u2009<0.005) were significantly associated with SI.'] Is impact of sleep on osteoporosis : sleep quality associated with bone stiffness index?