OBJECTIVES: A majority of patients with Parkinson's disease (PD) eventually develop gastrointestinal disorders (GID), which can impair the onset of symptom relief by PD drugs. There was a need to better understand the rate and consequences of GID amongst patients diagnosed with PD. METHODS: A two years matched retrospective cohort study was performed in a registered Pharmetrics® datacut, a US claims database containing records on demographics, diagnoses, procedures, provider, prescriptions and claims that span from 2000 to 2008. Patients with at least two prior diagnoses of Parkinson’s Disease, with continuous prescriptions of levodopa or dopamine agonists between September 1, 2005 and September 1, 2006 were selected. Patients with and without GID were matched by age, gender, comorbidities, and treatment regime. Their respective emerging health outcomes were followed-up for two years. Outcomes were defined on the basis of a literature review and included neuropsychiatric, motor, urogenital disturbances, healthcare utilization and related costs. RESULTS: In the datacut, GID incidence among patients with PD increased over time to stabilize at 75% at 92 months. 485 patients with PD and GID were matched to 485 controls with PD but without GID. GID was associated with significantly higher rates of neuropsychiatric and motor disorders, including psychosexual dysfunction (RR=8, p=0.05), anxiety (RR=1.61, p<0.01), depression (RR=1.28, p=0.03), ataxia (RR=1.24, p=0.03), pain (RR=1.28, p<0.01), movement disorders (RR=1.39, p<0.01), urinary incontinence (RR=1.43, p=0.02), and risk of fall (RR=1.44, p=0.04). ER admissions (ratio=1.42, p<0.01), number of concurrent drugs (ratio=1.06, p=0.04) and PD and non-PD healthcare costs (ratios= 1.13 and 1.12, p<0.01 respectively) increased during the observation period in the GID patients. CONCLUSIONS: GID have a substantial deleterious effect on major PD-related clinical and societal outcomes. Non oral formulations of PD drugs (apomorphine or L-dopa pumps or rotigotine)  may offer a good opportunity to bypass gastrointestinal tract, and accordingly maximize patient response to treatment.