Efficacy of Probiotics in Improving Motor Function and Alleviating Constipation in Parkinson's Disease: A Randomized Controlled Trial

Parkinson's disease (PD) is one of the common neurodegenerative diseases, and there has been an increasing interest in the potential role of intestinal dysbiosis in its pathogenesis and related gastrointestinal complications such as constipation. This study aims to evaluate the effects of multi-strain probiotics on constipation and motor function in PD patients. This study was a blinded, randomized controlled trial (RCT) that involved 27 PD patients who were diagnosed with constipation according to the ROME IV criteria for functional constipation. The primary outcome measured before and after the intervention in both the placebo and probiotic groups was the frequency of defecation. Secondary outcomes evaluated were laxative use, sense of complete evacuation, Bristol Stool Scale for consistency, and Unified Parkinson's Disease Rating Scale (UPDRS) scale. The study lasted for eight weeks. Both groups also were educated about lifestyle modification. Of 30 included patients (15 in each group), 13 were women, and 17 were men. Three patients dropped out of the study. Between-group analysis showed that the frequency of bowel movements significantly increased in the probiotic group 4 [3 - 5] in comparison with 2 [2 - 3] in placebo (P = 0.02). Stool consistency also improved in the probiotic group (P = 0.04). However, there were no significant differences in other outcomes. The within-group analysis showed improvement in stool consistency in both probiotics and placebo groups (P = 0.01 and P = 0.007, respectively), while stool frequency and sense of complete evacuation significantly improved only in the probiotic group (P < 0.05). This study demonstrated that multi-strain probiotics could improve frequency, consistency, and sense of complete evacuation in PD patients, while there was no significant effect on motor functions in 8 weeks. It is suggested that additional studies be conducted on longer-term effects.