Serum levels of interleukin-6 are elevated in patients with Parkinson's disease and correlate with physical performance.

Some studies have demonstrated altered circulating levels of cytokines, including IL-6, in Parkinson's disease (PD), implying a possible involvement of inflammatory and immune-mediated mechanisms in its pathogenesis. Moreover, the increased production of inflammatory cytokines has been associated with cognitive impairment and poor physical performance in the elderly. We compared serum levels of IL-6 in 44 PD patients and 22 healthy subjects, and correlated them with PD specific instruments and functional tests. Serum levels of IL-6 were significantly increased in PD (p=0.015). There was no correlation between serum levels of IL-6 and instruments traditionally used to assess PD severity. However, we found that PD patients with higher serum levels of IL-6 spent more time at functional mobility tests and had lower gait speed. Also, these patients had major problems to keep balance during functional tasks that required postural changes and that had a reduced base support. These results showed that high levels of IL-6 can be involved with an acceleration of muscle catabolism leading to sarcopenia, therefore contributing to weakness and fatigue, and may also be associated with functional disability in PD.