Table 1. Search strategy and keywords used and the resulting number of papers.

Search strategy	Database used	Number of results
(("tau proteins"[MeSH Terms]. AND "tau protein"[All Fields]. AND ("alphα-synuclein"[MeSH Terms]. AND "alphα-synuclein"[All Fields]. AND ("parkinson disease"[MeSH Terms]. AND "parkinson disease"[All Fields].)) AND (medline[sb]. AND "2013/04/25"[PDat]. : "2023/04/22"[PDat].)	PMC/Medline	61
tau protein AND alpha synuclein in parkinson disease	PubMed	234
(("tau proteins/adverse effects"[MeSH Terms]. OR "tau proteins/antagonists and inhibitors"[MeSH Terms]. OR "tau proteins/blood"[MeSH Terms]. OR "tau proteins/cerebrospinal fluid"[MeSH Terms]. OR "tau proteins/drug effects"[MeSH Terms]. OR "tau proteins/genetics"[MeSH Terms]. OR "tau proteins/therapeutic use"[MeSH Terms]. OR "tau proteins/toxicity"[MeSH Terms].) AND ("alpha synuclein/adverse effects"[MeSH Terms]. OR "alpha synuclein/antagonists and inhibitors"[MeSH Terms]. OR "alpha synuclein/blood"[MeSH Terms]. OR "alpha synuclein/cerebrospinal fluid"[MeSH Terms]. OR "alpha synuclein/drug effects"[MeSH Terms]. OR "alpha synuclein/genetics"[MeSH Terms]. OR "alpha synuclein/therapeutic use"[MeSH Terms]. OR "alpha synuclein/toxicity"[MeSH Terms].) AND ("parkinson disease/blood"[MeSH Terms]. OR "parkinson disease/cerebrospinal fluid"[MeSH Terms]. OR "parkinson disease/diagnosis"[MeSH Terms]. OR "parkinson disease/drug therapy"[MeSH Terms]. OR "parkinson disease/genetics"[MeSH Terms]. OR "parkinson disease/therapy"[MeSH Terms].)) AND ((y_10[Filter].) AND (fft[Filter].) AND (humans[Filter].) AND (english[Filter].))	PubMed MeSH	69
tau protein AND alpha synuclein in parkinson disease	Cochrane Library	10
Total		374
Total after removing duplicates		318