Parkinson's disease and fatigue.

Fatigue is one of the most common symptoms in patients with Parkinson's disease (PD), and its impact on the quality of life is substantial. However, its cause and treatment are not established. Fatigue in PD has two components, peripheral and central, which may be related to each other, but are more likely independent. Fatigue is partially associated with depression or sleep disorders, but patients with fatigue are not always depressed and do not necessarily have sleep problems. Anti-PD drugs may exacerbate or reduce fatigue. The impact of fatigue in PD is often underestimated by health-care providers.