Aims: Patients with lower-extremity fracture carry substantial long-term mortality, yet the contribution of modifiable pre-injury health parameters is rarely examined. We evaluated clinical characteristics before fracture as predictors of all-cause mortality.

Methods: Using the Korean National Health Insurance Service database, we identified adults aged ≥20 years who sustained a lower-extremity fracture during 2010–2017 and underwent national health screening within 2 years before the fracture. After exclusion of missing covariates, prevalent-event washout, and a 1-year lag, 273,986 patients were followed for all-cause mortality. Multivariable Cox proportional-hazards models estimated adjusted hazard ratios (aHR) with 95% confidence intervals, adjusting for age, sex, and clinical covariates.

Results: Over approximately 2.12 million person-years (mean follow-up 7.7 years), 46,899 deaths occurred (22.1 per 1,000 person-years). Mortality risk rose gradually with diabetes mellitus (DM) duration; the aHR was 1.33 (95%CI 1.29-1.38) for DM duration < 5years and 1.71 (1.67–1.76) for ≥5 years. Proteinuria independently predicted mortality (aHR 1.51, 1.45–1.56). BMI showed a reverse association: underweight (<18.5 kg/m²) increased risk (aHR 1.50, 1.45–1.56), whereas higher BMI was protective (≥30: aHR0.60, 0.56–0.64). Independent of BMI, central obesity conferred higher risk (waist circumference ≥100/95cm in men/women: aHR 1.27, 1.21–1.32). Regular exercise was associated with lower mortality (aHR 0.82, 0.80–0.84).

Conclusions: Among patients with lower-extremity fracture, longer diabetes duration, proteinuria, underweight, central obesity, and physical inactivity before injury independently predicted all-cause mortality. These parameters may aid risk stratification and secondary prevention in this population.