Summary: We identified a protective bone effect at the knee with lipophilic statin use in individuals with chronic spinal cord injury. Lipophilic statin users gained bone at the knee compared to non-users and wheelchair users lost bone compared to walkers. Ambulation and or statins may be effective osteogenic interventions in chronic spinal cord injury (SCI). Introduction: SCI increases the risk of osteoporosis and low-impact fractures, particularly at the knee. However, during the chronic phase of SCI, the natural history and factors associated with longitudinal change in bone density remain poorly characterized. In this study, we prospectively assessed factors associated with change in bone density over a mean of 21 months in 152 men and women with chronic SCI. Methods: A mixed model procedure with repeated measures was used to assess predictors of change in bone mineral density (PROC MIXED) at the distal femur and proximal tibia. Factors with a p value of <0.10 in the univariate mixed models, as well as factors that were deemed clinically significant (gender, age, and walking status), were assessed in multivariable models. Factors with a p value of ≤0.05 were included in the final model. Results: We found no association between bone loss and traditional osteoporosis risk factors, including age, gender, body composition, or vitamin D level or status (normal or deficient). In both crude and fully adjusted models, wheelchair users lost bone compared to walkers. Similarly, statin users gained bone compared to nonusers. Conclusions: The statin finding is supported by reports in the general population where statin use has been associated with a reduction in bone loss and fracture risk. Our results suggest that both walking and statins may be effective osteogenic therapies to mitigate bone loss and prevent osteoporosis in chronic SCI. Our findings also suggest that loss of mechanical loading and/or neuronal factors contribute more to disuse osteoporosis than traditional osteoporosis risk factors.
Bibliographical noteFunding Information:
We thank Rachael Burns and Kara Loo, research assistants, Boston VA Healthcare System, for collection of anthropometric data, and Merilee Teylan, Boston VA Healthcare System, analyst, for assistance with data cleaning and database management. Leslie Morse, Nguyen Nguyen, Ricardo Battaglino, A J Guarino, David Gagnon, Ross Zafonte, and Eric Garshick declare that they have no conflict of interest. This study received support from: The National Institute of Arthritis and Musculoskeletal and Skin Diseases [1R01AR059270-01], National Institute on Disability, Independent Living, and Rehabilitation Research (NIDILRR 90SI5007-01-02), The Office of Research and Development, Rehabilitation Research and Development [Merit Review Grant B6618R and RX-000792-01A2], and The Massachusetts Veterans Epidemiology Research and Information Center, Cooperative Studies Program, Department of Veterans Affairs.
- Rehabilitation medicine
- Spinal cord injury