This study aimed to clarify the risk of fragility fractures (FFs) in Japanese cancer survivors compared with individuals without cancer by incorporating time-dependent variables. In a 10-year cohort of 10,330 adults aged 40–69 years, we assessed the risk of FFs (i.e., hip, vertebral compression, and distal radius fractures) associated with cancer status by using time-dependent Cox proportional hazards analyses. The models were adjusted for demographic, lifestyle, and medical factors. The time-dependent variables included cancer status and age. Analyses were performed according to cancer treatment status, number of primary cancers, and cancer site. Among the 10,330 participants (mean age, 56.4 years; females, 6148), 386 experienced FFs. Compared with participants without cancer, a higher risk of overall FFs was observed in participants with cancer (hazard ratio [HR], 1.40; 95% confidence interval [CI], 1.03–1.89). This risk was further elevated among participants with active cancer (HR, 1.71; 95% CI, 1.15–2.55), multiple primary cancers (HR, 1.42; 95% CI, 1.04–1.95), stomach cancer (HR, 1.84; 95% CI, 1.01–3.37), kidney cancer (HR, 3.74; 95% CI, 1.20–11.70), and hematologic cancer (HR, 7.70; 95% CI, 2.45–24.16). These findings highlight the importance of FF prevention strategies in cancer survivorship care in aging Asian populations.
Supplementary Information: The online version contains supplementary material available at 10.1038/s41598-026-45389-1.
Keywords: Cancer; Fracture; Japanese; Prevention; Time-dependent variable.