Epidemiology of premenopausal osteoporosis in Japan: a retrospective cohort study based on real-world data

We aimed to characterize the clinical features of premenopausal osteoporosis in Japan and evaluate medical interventions after fracture diagnosis. From a nationwide Japanese administrative claims database, we extracted 105,931 records of women regarding date of childbirth and divided them into two groups based on presence of a fragility fracture diagnostic code. From the records, we identified 231 women who had suffered a low-trauma fracture at reproductive age as the case group, and we randomly selected 1000 women as the control group. Age at childbirth was significantly higher ( P = 0.00146) and estrogen-deficient conditions were significantly more frequent in the case than in the control group (odds ratio = 2.97, 95% confidence interval: 1.57–5.63). The most common fracture site was the vertebrae (35.2%), and fractures were also frequent in the 18 months around childbirth (32.9%). More than half of these fracture types overlapped, with significantly more opportunities for bone densitometry, an osteoporosis diagnosis, and antiosteoporosis pharmacotherapyfor these than for other fracture types, which were seldom treated as osteoporosis. Therefore, vertebral fractures and fracturesaround childbirth are a representative subtype of premenopausal osteoporosis. More medical attention isrecommended for all cases of premenopausal osteoporosis to reduce future fracture risk.