| Objective Osteoporosis is a common and significant health concern among middle-aged and older adults. Impaired lung function may have a potential impact on bone health. This study aimed to systematically explore the relationship among lung function parameters, bone mineral density (BMD), and osteoporosis based on data from the 2007–2010 National Health and Nutrition Examination Survey (NHANES). Methods This cross-sectional study included 3,547 adults aged 50 years and older. Lung function was assessed using forced expiratory volume in one second (FEV1), forced vital capacity (FVC), and the FEV1/FVC ratio. BMD was measured at the femoral neck. Osteoporosis was diagnosed according to the World Health Organization (WHO) criteria. Multivariable logistic regression models were used to analyze the association between lung function and osteoporosis, adjusting for potential confounders such as age, sex, race, smoking, alcohol consumption, body mass index (BMI), and comorbidities. A hexbin plot was used to illustrate the joint distribution of lung function and BMD. A restricted cubic spline (RCS) model was applied to assess nonlinear relationships between lung function and osteoporosis. Subgroup analyses were performed. A forest plot was used to display the association between FEV1/FVC and osteoporosis risk across different population subgroups. Results Lower lung function was significantly associated with an increased risk of osteoporosis. Participants in the highest quartile of FEV1/FVC had a 50% lower risk of osteoporosis (OR = 0.50, 95% CI: 0.29–0.85, P=0.015). Baseline analysis showed that osteoporosis patients had a significantly lower FEV1/FVC value (0.71 ± 0.10) than those without osteoporosis (0.75 ± 0.09, P<0.001). RCS analysis revealed significant nonlinear relationships between FEV1/FVC (P=0.014) and FVC (P=0.239) with osteoporosis risk, while the nonlinear association for FEV1 was weaker (P=0.195). Subgroup analysis results were consistent across various populations, supporting the robustness of the association. Conclusion Among middle-aged and older adults, reduced lung function (as indicated by lower FEV1, FVC, and FEV1/FVC) is closely associated with an increased risk of osteoporosis. These findings suggest that routine lung function monitoring may serve as an important strategy for the early prevention and intervention of osteoporosis. |