Additional Table 1.

Newcastle-Ottawa Scale Assessment of Case-Control Studies

Articale	Selection										Combarability		Exposure									Scores
	Case Definition			Representativeness of the cases		Selection of controls			Definition of controls				Ascertainment of exposure				Same determination method adoption		Non-response rate
	Requires some independent validation	Record linkage	No description	All eligible cases with outcome of interest over a defined period of time	Not satisfying requirements or not stated	Community controls	Hospital controls	No description	No history of Parkinson’s disease	No mention of source	Intakes of fat	Other controlled factors	Reliable record	Structured survey	Written self-report or medical record	No description	Yes	No	Identication	No description	Unidentication and have no expalnation
Logroscino et al. (1996)	☆			☆					☆		☆		☆				☆		☆			7
Hellenbrand et al. (1996)	☆			☆		☆			☆		☆	☆	☆				☆		☆			9
Powers et al. (2009)	☆			☆		☆			☆		☆	☆	☆				☆		☆			9
Miyake et al. (2010)	☆			☆		☆			☆		☆	☆	☆				☆		☆			9
Kamel et al. (2015)	☆			☆					☆		☆		☆				☆		☆			7