Lower Frequency of co-Morbid Medical Disorders Related to Poor Impulse Control in Parkinson's than Alzheimer's...

Parkinson's disease is associated with progressive degeneration of mesolimbic dopaminergic neurons that are involved in reward-based behavior learning, including rewarding effects of food consumption and drugs of abuse. The importance of this pathway in development of addictive behaviors led us to hypothesize that medical disorders related to poor impulse control may occur less frequently among patients with Parkinson's disease than those with other progressive neurodegenerative disorders such as Alzheimer's disease. Retrospective cross-sectional study of all patients treated for Parkinson's disease and Alzheimer's disease in a community based clinic during a two-year period. Associations were summarized using odds ratios (OR) and 95% confidence intervals (95% CI) estimated from logistic regression models, adjusted for differences in gender distribution between the groups. A total of 106 patients with Parkinson's disease and 72 patients with Alzheimer's disease were included. Patients with Parkinson's disease were less likely to have either past substance use (adjusted OR = 0.035, 95% CI = 0.009 - 0.130) or presence of co-morbid medical conditions related to poor dietary choices (adjusted OR = 0.157, 95% CI = 0.062 - 0.397). Co-morbid medical conditions related to poor impulse control occur less frequently among those with Parkinson's disease than those with Alzheimer's disease. These findings are consistent with dysfunction of dopamine dependent pathways involved in addiction during the presymptomatic phase of Parkinson's disease and support a biological basis for addiction.