Prevalence and regional distribution of osteoporosis in adults aged 75 years and older: a quantitative computed tomography-based retrospective cross-sectional study.

PURPOSE: This study aimed to determine the prevalence of osteoporosis (OP) in patients aged ≥ 75 years using quantitative computed tomography (QCT) and to evaluate the scientific rationale for the approach of “initiating OP treatment without measurement in patients aged 75 and older” as stated in the Turkish Health Practice Bulletin. METHODS: This retrospective cross-sectional study included 1,531 patients aged ≥ 75 years (mean age 79.2 ± 4.2 years; 91.9% Women) who underwent QCT measurements at a tertiary hospital between January 2023 and August 2025. Lumbar trabecular volumetric bone mineral density (vBMD) and hip areal BMD (aBMD) were assessed. OP classification was performed using American College of Radiology (ACR) standardized BMD thresholds (< 80 mg/cm³) for lumbar spine and T-scores for hip regions. We conducted a study using routinely collected electronic health records (EHR) and Picture Archiving and Communication System (PACS) data at a tertiary hospital in Istanbul. RESULTS: Mean lumbar QCT vBMD was 77.9 ± 28.6 mg/cm³. OP prevalence in the lumbar spine was 85.0% based on T-score but 58.5% based on ACR BMD criteria, revealing a 26.5% discrepancy (Cohen’s κ = 0.317, p < 0.001). Among 1,301 patients classified as osteoporotic by T-score, 31.5% (n = 410) were in the osteopenia range according to QCT BMD criteria. At least one region showed OP in 66.2% of patients. OP prevalence increased significantly with age (75–79 years: 50.7%; 80–84 years: 69.7%; ≥85 years: 74.1%; p < 0.001). Women had significantly higher OP prevalence than men (59.6% vs. 46.0%, p < 0.001). Substantial regional discordance was observed between lumbar and hip measurements (54.5% for total hip, 56.6% for femoral neck; p < 0.001), with nearly half of lumbar osteoporotic patients (48.4%) showing only osteopenia in the hip. CONCLUSION: OP prevalence is very high in individuals aged ≥ 75 years, supporting the rationale for empirical treatment without mandatory measurement. QCT evaluation should be based on volumetric BMD values rather than T-scores to avoid false-positive diagnoses. The substantial regional discordance emphasizes the importance of multi-site assessment when measurements are performed.