**5. Conclusions**

In conclusion, the present evidence supports a link between PD and PAOD. Further studies which address the temporality of PD and PAOD are warranted. Thus, a causal, or at least, an important contributing role of PD in the development of PAOD can currently not be confirmed but may be suspected. Clearly, the ultimate proof of causality would depend on data from randomized controlled invention trials to show that treatment of PD can diminish or even prevent PAOD. Such data does, to the best of our knowledge, currently not exist.

### **Supplementary Materials:** Supplementary Materials can be found at http://www.mdpi.com/1422-0067/20/12/ 2936/s1.

**Funding:** This work was supported by the Innovation Fund of the Joint Federal Committee, Berlin, Germany [grant number 01VSF16008] and the Else Kröner-Fresenius-Foundation, Bad Homburg, Germany [grant number 2016\_A166].

**Conflicts of Interest:** The authors declare no conflict of interest.
