In the case of genomic regions with known genetic factors in PD, a systematic review and meta-analysis with more than 70,000 participants describes genetic variants in genes such as IL-1A, IL-1B, IL-6, IL-10, MMP-3, and MMP-9 were significantly associated with the risk of developing periodontitis (da Silva et al., 2017). Here, IL1A is linked to Parkinson disease.