The Association between Toxoplasma gondii Infection and Risk of Parkinson’s Disease: A Systematic Review and Meta-Analysis

Abstract

Background. Several studies have investigated the association between Toxoplasma gondii (T. gondii) infection and risk of Parkinson’s disease (PD) with inconsistent results. Clarifying this relation might be useful for better understanding of the risk factors and the relevant mechanisms of PD, thus a meta-analysis was conducted to explore whether exposure to T. gondii is associated with an increased risk of PD. Methods. We conducted this meta-analysis according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement. A rigorous literature selection was performed by using the databases of PubMed, Embase, Web of Science, Cochrane Library, and ScienceDirect. Odds ratio (OR) and corresponding 95% confidential interval (CI) were pooled by using fixed-effects models. Sensitivity analysis, publication bias test, and methodological quality assessment of studies were also performed. Results. Seven studies involving 1086 subjects were included in this meta-analysis. Pooled data by using fixed-effects models suggested both latent infection (OR, 1.17; 95% CI, 0.86 to 1.58; P=0.314) and acute infection (OR, 1.13; 95% CI, 0.30 to 4.35; P=0.855) were not associated with PD risk. Stable and robust estimates were confirmed by sensitivity analysis. No publication bias was found by visual inspection of the funnel plot, Begg’s, and Egger’s test. Conclusions. This meta-analysis does not support any possible association between T. gondii infection and risk of PD. Researches are still warranted to further explore the underlying mechanisms of T. gondii in the pathogenesis of PD and their causal relationship.

Neurological and Neurobehavioral Disorders Associated with Toxoplasma gondii Infection in Humans

“…Furthermore, Mahami-Oskouei et al discovered a statistically significant association between Parkinson's disease and owning a cat ( p = 0.03) although the T. gondii status of owned cats was not established. However, Mahami-Oskouei et al found no significant association between IgG-positive titers and Parkinson's disease [ 163 ], and the meta-analysis conducted by Zhou et al concluded that there is no linkage between PD risk and T. gondii infection [ 164 ]. While multiple studies suggest no significant linkage between PD and T. gondii infection [ 48 , 165 , 166 ], Ramezani et al found higher anti- Toxoplasma IgG antibodies in patients with idiopathic PD.…”

Latent Toxoplasmosis Effects on Rodents and Humans: How Much is Real and How Much is Media Hype?

“…Several publications reported a positive correlation between PD and T. gondii seropositivity (83,84), although they were quickly followed by negative studies (85,86). In a recent meta-analysis on PD and T. gondii seropositivity, Zhou et al included seven studies with 1,086 subjects total and found no correlation between PD and T. gondii seropositivity (87). This meta-analysis highlighted that the initial positive studies for PD had small sample sizes and likely some degree of sampling bias related to the geographical region in which the studies were conducted.…”

Non-Genetic Risk Factors for Parkinson’s Disease: An Overview of 46 Systematic Reviews

“…Numerous systematic reviews (SRs) and metaanalyses on non-genetic risk factors for PD development have been published [13][14][15][16][17][18][19][20], with several inconsistent results. For example, one SR found that diabetes decreased the risk of PD [21], while another did not confirm this association [22].…”