Cognitive impairment is associated with reduced bone mass in multiple sclerosis.

Background: Multiple sclerosis (MS) has been associated with reduced bone mineral density (BMD), yet the underlying causes are not fully known. The recent discovery that bone homeostasis is directly regulated by the brain led us to hypothesize that it may be impaired by MS pathology. As cognitive impairment (CI) is a well-documented correlate of MS-related brain pathology, we tested the hypothesis that it is associated with reduced BMD.

Objective: We aimed to determine if CI is associated with reduced BMD in patients with MS.

Methods: We retrospectively studied the medical records of 56 patients with MS, ≤50 years old, with Expanded Disability Status Scale score ≤4.5 and with dual X-ray absorptiometry (DEXA) BMD measurement within 1 year of neuropsychological testing with a standard battery (MACFIMS).

Results: In total, 23 (41.1%) MS patients had osteopenia or osteoporosis. Mean femur BMD was significantly lower in patients with MS with CI (0.89±0.12 g/cm(2)) compared with intact patients (0.99±0.17 g/cm(2), p=0.009). In the cognitively impaired group, 59.3% had either osteopenia or osteoporosis, compared with 24.1% in the non-cognitively impaired group (odds ratio=4.57, p=0.008).

Conclusion: CI is associated with reduced BMD in patients with MS, suggesting that central mechanisms involved in bone homeostasis may be directly impaired by MS-related inflammatory and neurodegenerative processes.