Weight Loss in Parkinson's Disease: No Evidence for Role of Small Intestinal Bacterial Overgrowth.

Background and Objective: Weight loss and small intestinal bacterial overgrowth (SIBO) are common in Parkinson's disease (PD). We aimed to study the relationship between weight loss and SIBO in PD. Methods: This was a cross-sectional study with a prospective, interventional component. Consecutive patients seen in the PD clinic who agreed to participate underwent extensive history, movement exam, SIBO breath testing and answered questionnaires. A subset of those in the weight loss group were treated with rifaximin for 14 days and returned 3 months later for an assessment of their weight, GI symptoms, quality of life and SIBO status. All analyses were adjusted for age and disease duration. Results: Fifty-one patients participated in the study; 37 without weight loss and 14 with weight loss. Total energy intake including the distribution of macronutrient intake was similar between groups while physical activity was less in those with weight loss. PD severity scores did not differ between groups; however, PD-specific quality of life scores were significantly worse for the summary index and the subscales of emotional well-being, social support and communication. The prevalence of constipation, dyspepsia and abdominal pain/discomfort was higher in those with weight loss. The prevalence of SIBO was 14% in the weight loss group and was not different between groups. Eight PD patients with weight loss were treated with rifaximin; no significant change in GI symptoms, quality of life or weight was seen 3 months later. Conclusion: Although a number of differences were identified in quality of life and gastrointestinal symptoms between groups with and without weight loss, SIBO was not associated with weight loss in patients with PD. Given the exploratory nature and small number of patients with weight loss, however, further study is suggested.