Meta-analysis of the relations between gut microbiota and pathogens and Parkinson's disease

The motor symptoms in patients with Parkinson's disease (PD) are commonly preceded by gastrointestinal (GI) symptoms. The enteric nervous system (ENS) has also been reported to exhibit neuropathological characteristics of PD.

To evaluate the relationship between the incidence of parkinsonism and alteration in gut microbiota and pathogens.

Studies in different languages that evaluate the relationship between gut microorganisms and PD were included into this meta-analysis. The outcomes of these studies were analyzed using a random effects model; it was also used to calculate the mean difference (MD) with 95% confidence interval (95% CI) in order to quantify the impact of different rehabilitation techniques on clinical parameters. Dichotomous and continuous models were used for the analysis of extracted data.

A total of 28 studies were included in our analysis. The analysis of small intestinal bacterial overgrowth showed a significant correlation with Parkinson's subjects compared with controls (p < 0.001). In addition, the presence of Helicobacter pylori (HP) infection was significantly related to the Parkinson's group (p < 0.001). On the other hand, there was a significantly higher abundance level of Bifidobacteriaceae (p = 0.008), Verrucomicrobiaceae (p < 0.001) and Christensenellaceae (p = 0.003) in Parkinson's subjects. In contrast, a significantly lower abundance levels in Parkinson's subjects were found in Faecalibacterium (p = 0.03), Lachnospiraceae (p = 0.005) and Prevotellaceae (p = 0.005). No significant difference was related to Ruminococcaceae.

Parkinson's subjects showed a higher degree of alteration of gut microbiota and pathogens compared with normal human subjects. Future multicenter randomized trials are needed.