Development of Functional Performance, Bone Mineral Density, and Back Pain Under Specific Pharmacological Osteoporosis Therapy in an Elderly, Multimorbid Cohort

Background/Objectives: Specific pharmacological osteoporosis therapy (SPOT) is regarded as a key intervention to reduce fracture risk and improve musculoskeletal function. Real-life data, particularly regarding functional muscular outcomes and pain trajectories, remain limited. This study aimed to longitudinally analyze bone mineral density, laboratory parameters, handgrip strength, functional performance, and pain symptoms under guideline-based SPOT. Methods: In this monocentric prospective real-life observational study, 178 patients (80.9% women; median age 82 years) with confirmed osteoporosis were followed for a median of four years. All patients received guideline-recommended antiresorptive or osteoanabolic therapy. Analyses included T-scores, 25(OH)D, calcium, handgrip strength, Chair Rise Test (CRT), tandem stance (TS), pain parameters, alkaline phosphatase (AP), HbA1c, fractures, comorbidities, and body mass index (BMI). Time-dependent changes were evaluated using linear mixed-effects models. Results: Bone mineral density improved highly significantly (ΔT-score ≈ +0.45 SD; p < 0.001), with no differences between therapy groups (antiresorptive vs. osteoanabolic) or BMI categories. Serum 25(OH)D levels increased markedly (Δ ≈ +20 nmol/L; p < 0.001), while calcium levels showed a small but highly significant decrease (Δ ≈ −0.047 mmol/L; p < 0.001), particularly under antiresorptive treatment. Dominant (Δ ≈ −1.95 kg; p < 0.001) and non-dominant handgrip strength (Δ ≈ −0.83 kg; p = 0.046) decreased significantly. In contrast, functional performance improved significantly: CRT time decreased by ~1 s (p = 0.004), and TS time increased by ~1 s (p = 0.007). Back pain decreased highly significantly (Δ ≈ −1.5 NRS; p < 0.001), while pain-free walking time (Δ ≈ +38 min; p = 0.031) and pain-free standing time (Δ ≈ +31 min; p = 0.038) both increased significantly. AP levels decreased significantly (p = 0.003), particularly among normal-weight patients. HbA1c changes were not significant. Overall, 73% of patients had at least one major osteoporotic fracture. Conclusions: In this real-life cohort, guideline-based specific pharmacological osteoporosis therapy was associated with significant improvements in bone mineral density, vitamin D status, functional performance, and pain-related outcomes. Despite a moderate decline in handgrip strength, balance- and mobility-related functional parameters improved, suggesting preserved or even enhanced functional capacity in daily life. These findings provide real-world evidence on the associations between SPOT, laboratory parameters, functional performance, and pain outcomes in a very elderly and multimorbid population.