The role of income and educational level as risk factors for atypical femur fractures: A Nationwide Danish Case-Cohort Study with Blinded Radiographic Review
14 affiliations
- 1Research Unit OPEN, Department of Clinical Research, University of Southern Denmark and Odense University Hospital, Odense, Denmark
- 2Department of Orthopedic Surgery, Gävle Hospital, Gävle, Sweden
- 3Centre for Research and Development, Region Gävleborg, Uppsala University, Gävle, Sweden
- 4Clinical Department of Orthopaedics in Linköping, Region Östergötland, Linköping, Sweden
- 5Department of Biomedical and Clinical Sciences, Linköping University, Linköping, Sweden
- 6Department of Epidemiology & Biostatistics, University of California, San Francisco, USA
- 7Department of Radiology and Biomedical Imaging, University of California, San Francisco, USA
- 8Department of Radiology, Aarhus University, Aarhus, Denmark
- 9Departments of Radiology and Clinical Medicine, Aalborg University Hospital, Aalborg, Denmark
- 10Department of Radiology, Copenhagen University Hospital, Bispebjerg and Frederiksberg, Denmark
- 11Department of Research & Evaluation, Kaiser Permanente Southern California, Pasadena, CA USA
- 12Department of Medicine, University of California, San Francisco, USA
- 13Department of Public Health, University of Southern Denmark, Odense, Denmark
- 14Research Unit OPEN, Department of Clinical Research, University of Southern Denmark, Odense University Hospital and Holbæk Hospital, Odense, Denmark
Abstract
Socioeconomic factors and atypical femur fracture (AFF) risk during bisphosphonate treatment are poorly understood. Among Danish bisphosphonate users, medium, and long educational levels were associated with lower AFF rates, with medium education remaining associated with lower AFF risk after adjustment, even within a universal healthcare system.
Purpose: Atypical femur fracture (AFF) is a rare but serious fracture type associated with bisphosphonate (BP) treatment. While clinical risk factors are well studied, socioeconomic factors among BP users remain unexplored. We therefore examined whether income and educational level were associated with AFF risk in Denmark.
Methods: We included all radiologically confirmed AFF cases from 2010 to 2014, identified through blinded reviews of potential AFFs among individuals aged ≥ 50 years, and register-data for a random sample of the general population ≥ 50 (n = 100,253). Health, income, and education data were obtained from Danish national registers. We estimated incidence rates (IR), incidence rate ratios (IRR), and hazard ratios (HR) using Cox regression.
Results: Among 164 AFF cases, 116 had BP exposure, and exposure was higher among AFF cases than in the background population (70.7% vs. 7.9%, p < 0.05). The AFF IR among BP users was 32.5 per 10,000 person-years (CI 27.1–39.0). Crude AFF rates differed by income and education, but income was not associated with AFF risk in adjusted Cox regression. BP users with medium or long education had a lower IRR than those with low/missing education (medium: IRR (CI): 0.56 (0.36–0.86); long: IRR (CI): 0.53 (0.28–0.95)). In age- and sex-adjusted Cox analyses, medium education remained associated with a lower AFF risk 0.63 (0.41–0.96).
Conclusion: Socioeconomic differences in AFF rates were observed among BP users, but adjusted analyses did not support an independent association between income and AFF risk. Medium education was associated with lower AFF risk after adjustments.
Supplementary Information: The online version contains supplementary material available at https://doi.org/10.1007/s00198-026-08156-6.
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BibTeX
@article{leth2026role,
title = {{The role of income and educational level as risk factors for atypical femur fractures: A Nationwide Danish Case-Cohort Study with Blinded Radiographic Review}},
author = {Kasper Westphal Leth and Benjamin Bakke Hansen and Hans Peter Bögl and Daphne Wezenberg and Austin R. Thompson and Richard Dell and Bo Fan and Anne Grethe Jurik and Jens Brøndum Frøkjær and Mikael Ploug Boesen and Annette L. Adams and Jörg Schilcher and Dennis M. Black and Douglas C. Bauer and Bo Abrahamsen},
journal = {Osteoporosis International},
year = {2026},
month = jul,
doi = {10.1007/s00198-026-08156-6},
url = {https://doi.org/10.1007/s00198-026-08156-6},
note = {CC BY-NC 4.0},
}
RIS
TY - JOUR
TI - The role of income and educational level as risk factors for atypical femur fractures: A Nationwide Danish Case-Cohort Study with Blinded Radiographic Review
AU - Kasper Westphal Leth
AU - Benjamin Bakke Hansen
AU - Hans Peter Bögl
AU - Daphne Wezenberg
AU - Austin R. Thompson
AU - Richard Dell
AU - Bo Fan
AU - Anne Grethe Jurik
AU - Jens Brøndum Frøkjær
AU - Mikael Ploug Boesen
AU - Annette L. Adams
AU - Jörg Schilcher
AU - Dennis M. Black
AU - Douglas C. Bauer
AU - Bo Abrahamsen
PY - 2026
DA - 2026/07/24
JO - Osteoporosis International
DO - 10.1007/s00198-026-08156-6
UR - https://doi.org/10.1007/s00198-026-08156-6
AB - Socioeconomic factors and atypical femur fracture (AFF) risk during bisphosphonate treatment are poorly understood. Among Danish bisphosphonate users, medium, and long educational levels were associated with lower AFF rates, with medium education remaining associated with lower AFF risk after adjustment, even within a universal healthcare system. Purpose: Atypical femur fracture (AFF) is a rare but serious fracture type associated with bisphosphonate (BP) treatment. While clinical risk factors are well studied, socioeconomic factors among BP users remain unexplored. We therefore examined whether income and educational level were associated with AFF risk in Denmark. Methods: We included all radiologically confirmed AFF cases from 2010 to 2014, identified through blinded reviews of potential AFFs among individuals aged ≥ 50 years, and register-data for a random sample of the general population ≥ 50 (n = 100,253). Health, income, and education data were obtained from Danish national registers. We estimated incidence rates (IR), incidence rate ratios (IRR), and hazard ratios (HR) using Cox regression. Results: Among 164 AFF cases, 116 had BP exposure, and exposure was higher among AFF cases than in the background population (70.7% vs. 7.9%, p < 0.05). The AFF IR among BP users was 32.5 per 10,000 person-years (CI 27.1–39.0). Crude AFF rates differed by income and education, but income was not associated with AFF risk in adjusted Cox regression. BP users with medium or long education had a lower IRR than those with low/missing education (medium: IRR (CI): 0.56 (0.36–0.86); long: IRR (CI): 0.53 (0.28–0.95)). In age- and sex-adjusted Cox analyses, medium education remained associated with a lower AFF risk 0.63 (0.41–0.96). Conclusion: Socioeconomic differences in AFF rates were observed among BP users, but adjusted analyses did not support an independent association between income and AFF risk. Medium education was associated with lower AFF risk after adjustments. Supplementary Information: The online version contains supplementary material available at https://doi.org/10.1007/s00198-026-08156-6.
SN - 0937-941X
SN - 1433-2965
ER -