Can levodopa prevent cognitive decline in patients with Parkinson's disease?

Cognitive impairment in Parkinson's disease (PD) will become more important since the number of elderly patients with PD is increasing. We prospectively studied non-demented patients with PD over the course of 3 years to identify factors associated with PD that contribute to a decline in cognitive function. From among 100 consecutive patients, we registered 79 patients with PD. A total of 55 patients completed the study during 3 years and were divided to two groups: patients with a decline in cognitive function and those without a decline in cognitive function after 3 years. Seventeen independent variables were evaluated with the use of logistic regression models. The increase in the daily levodopa dose was related to a decline in cognitive function on univariate logistic regression analysis (OR = 0.279, p = 0.024, 95% CI = 0.092-0.848). Other variables were not related to a decline in cognitive function. The increase in the daily dose of levodopa was greater in patients without a decline in cognitive function than those with a decline in cognitive function; on the other hand, the cognitive function unchanged. Our results suggest that the treatment with levodopa might prevent a decline in cognitive function in PD.