Parkinson's disease: A risk factor for osteoporosis.

Parkinson's disease is the most common neurodegenerative disease after Alzheimer's disease. On the long term, it may be complicated by various musculoskeletal problems, such as osteoporotic fractures, that have significant socioeconomic consequences. Indeed, patients suffering from Parkinson's disease have a higher fracture risk, particularly hip fracture risk, than other subjects of the same age because of both a higher risk of falls and lower bone mineral density. Bone loss in Parkinson's disease may be associated with the severity and duration of the disease. We review here the different suspected mechanisms of accelerated bone loss in Parkinson's disease, amongst which weight loss and reduced mobility appear to play key roles. Antiparkinsonian drugs, particularly levodopa, may also be associated with decreased bone mineral density as a result of hyperhomocysteinaemia. We discuss the role of other nutritional deficiencies, such as vitamin B12, folate or vitamin K. In conclusion, it seems necessary to screen for and treat osteoporosis in this at-risk population, while actions to prevent falls are still disappointing. A better understanding of the factors explaining bone loss in this population would help implementing preventive actions.