Table 3.

Studies investigating the association between anemia and Parkinson’s disease.

Study	Study design	Main results
Logroscino et al. (2006)	Prospective, case-control, USA	Multiple blood donations are associated with an increased risk of PD in men.
Savica et al. (2009)	Retrospective, case-control, USA	Anemia is associated with an increased risk of PD.
Hong et al. (2016)	Retrospective, case-control, Taiwan	Anemia is associated with an increased risk of PD. PD might develop 4 years or more after the initial diagnosis of anemia.
Deng et al. (2017)	Case-control, China	Hemoglobin levels are lower in PD patients and are associated with disease severity.