The purpose of this study is to evaluate the microbiome of medicated and non-medicated subjects diagnosed with Parkinson's disease. Where available, in comparison to the microbiome of a healthy spouse or 1st degree relative.

First, a cross sectional study where the investigators will compare microbiome composition in subsets of PD and Multiple System Atrophy (MSA) patients whose household control agree to provide stool samples as well. Each household control subject will be evaluated to ensure there is no clinical evidence of neurological disorders including PD. Also, these subjects will complete a 24 hour diet recall questionnaire before stool collection and validated 3 month food frequency questionnaire to collect dietary information similar to PD patients. Each subject (including PD subjects) will complete a smell questionnaire and a sleep questionnaire to determine whether these "control" subjects have loss of smell or have REM sleep disorders because these conditions increase the risk of PD. For assessing smell, investigators will use the UPSIT questionnaire. For assessing REM sleep disorder, investigators will use RBD1Q which consists of a single question, answered "yes" or "no," as follows: "Has the subject ever been told, or suspected themselves that they seem to 'act out their dreams' while asleep (for example, punching, flailing their arms in the air, making running movements, etc.)?"

Second, in the longitudinal study, the investigators will collect stool every 3 months with 3 day diet questionnaire prior to each collection over 12 months and determine microbiome composition over time. Investigators will correlate the microbiome data with PD symptoms, diet and response to treatment and progression of disease. These studies will determine whether disease progression and factors such as PD medications and diet significantly impact microbiome composition. Furthermore, the investigators will determine whether changes in SCFA-producing bacteria and/or abnormal SCFA profiles correlate with severity of PD symptoms.

Inclusion Criteria:

PD Subjects Inclusion:

• 40-80 years of age
• Previously diagnosed with Parkinson's disease
• Parkinson's disease stage between 1-4
• Are willing to participate in the study

Healthy control/ Spouse/ 1st degree relative Inclusion:

• Adults 40-80 years of age
• No clinical evidence of neurological disorders including Parkinson's disease
• Live in the same household as the Parkinson Disease patient or is a first degree relative of the PD patient or an independent healthy control
• Are willing to participate in the study

Exclusion Criteria:

PD Subjects Exclusion:

• History of GI diseases (except for hemorrhoids or occasional (<3 times a week) heartburn) like Inflammatory bowel disease or Celiac disease.
• Antibiotic use within last 12 weeks.
• Use of probiotic supplement except yogurt.
• Intentional change in diet.
• Chronic use of NSAIDS. A washout period of 3 weeks is needed before the subject could be enrolled into the study. Low dose aspirin is allowed.

Healthy control/ Spouse/ 1st degree relative Exclusion:

• History of GI diseases (except for hemorrhoids or occasional (<3 times a week) heartburn) like Inflammatory bowel disease or Celiac disease.
• Antibiotic use within last 12 weeks.
• Use of probiotic supplement except yogurt.
• Intentional change in diet.
• Chronic use of NSAIDS. A washout period of 3 weeks is needed before the subject could be enrolled into the study. Low dose aspirin is allowed

Population will be selected from the neurology clinic, as well as a self-referrals.

No identifying information will be shared with other researchers.