Elevated homocysteine levels have been associated with an increased risk of dementia and Alzheimer disease

Patients with Parkinson disease (PD) who also have high levels of homocysteine (an amino acid produced by the body) are more likely to be depressed compared with other patients with PD who have normal levels of homocysteine, according to an article in the June issue of the Archives of Neurology, one of the JAMA/Archives journals.

According to information in the article, elevated homocysteine (Hcy) levels have been associated with an increased risk of dementia and Alzheimer disease. High concentrations of Hcy have been associated with a decrease in cognitive functioning, even in elderly patients without dementia, the article states. PD patients in particular are at risk for elevated levels of Hcy because the metabolism of levodopa, a drug commonly used to treat the disease, produces Hcy.

Padraig E. O'Suilleabhain, M.B., B.Ch., of The University of Texas Southwestern Medical Center at Dallas, and colleagues examined whether high Hcy levels were associated with depression or with cognitive, or physical impairments in patients with PD.

The researchers studied 97 patients with an average duration of PD of 3.6 years. Patients were divided into two groups: those with normal Hcy levels (n=66) and those with elevated Hcy levels (n=31). Participants completed a depression survey and underwent a variety of cognitive and motor tests. Fifty-four participants were taking levodopa.

"An elevated plasma Hcy concentration … was present in 31 (32 percent) of our 97 patients with fairly recent onset PD," the authors write. "An elevated Hcy level is most likely due to the prevalent use of levodopa: as in previous studies, the patients taking levodopa had higher Hcy levels than those not taking levodopa."

The researchers found that patients with elevated Hcy levels were slightly older (68 vs. 62 years), were more depressed, and had worse cognitive functioning, but had no difference in physical functioning measures.

"Our findings, if confirmed, indicate that disease burden in PD patients, such as poor motor performance, depression, and cognitive deterioration, is associated with a high Hcy level," the researchers conclude.