The study, “Gout and the risk of Parkinson’s disease in older adults: a study of U.S. Medicare data” was published in BMC Neurology.
Parkinson’s disease is a progressive neurological disorder that mainly affects motor function due to the loss of nerve cells in the brain that produce dopamine. When dopamine-producing neurons die, it causes symptoms such as tremors, stiffness, and balance problems.
About 1 percent of the population older than 60 are diagnosed with Parkinson’s. Due to this low incidence, risk factors for the disease have not been fully explored. It is known, however, that herbicide or pesticide exposure, along with hypertension, are potential risk factors for developing Parkinson’s. Inversely, use of statins (lipid-lowering medicines) and smoking are thought to lower the risk of developing the disease.
Previous studies have attempted to associate the levels of urate — a salt derived from uric acid — in the blood with the risk of developing Parkinson’s. Urate has an antioxidant effect that researchers think may help prevent the disease. As a result, lower levels of serum urate could lead to a higher Parkinson’s prevalence. However, so far, studies have not been able to confirm this association.
Gout is an inflammatory arthritis disease caused by increased oxidative stress and chronic inflammation, factors that can potentially increase the risk for Parkinson’s disease. Oxidative stress is an imbalance between the production of free radicals and the ability of cells to detoxify them. These free radicals or reactive oxygen species are harmful to cells and are associated with a number of diseases.
However, in a patient who has gout, serum urate levels are actually increased. “Acute and chronic inflammatory state in gout might potentially negate the anti-oxidant effects of urate, if one exists physiologically,” the researchers wrote.
Whether there is an association between urate and Parkinson’s risk in gout patients is still a matter of controversy.
In this study, researchers at the University of Alabama at Birmingham aimed to clarify the existence of a possible association between gout and Parkinson’s, taking into account other known risks for the disease such as age, sex, hypertension, hyperlipidemia (high levels of fat, also called lipids, in the blood), statin use, and demographic variables.
Using a random sample encompassing 5% of Medicare claims data, acquired from 2006 to 2012, a total of 1.72 million people — 1.63 million without gout and 94,133 with gout — were analyzed. Their mean age was 75.3 years, 58% were female, 36% were white, and they had a mean Charlson-Romano comorbidity index score — which predicts 10-year mortality — of 1.6.
The analysis was adjusted for statin use and cardiovascular disease, two potential confounding variables of Parkinson’s risk, as well as for the use of urate-lowering therapy.
A total of 22,636 people developed incident Parkinson’s disease — 21,507 without gout and 1,129 with gout. Older age, male gender, white race, and higher Charlson-Romano comorbidity index score were associated with a higher risk of Parkinson’s.
The analysis revealed that gout was independently linked to a 1.14 times higher risk of Parkinson’s. The risk differed significantly by age, with patients between the ages of 65 and 75 having the highest risk (1.27 times higher) and those older than 85 having a smaller risk (0.97). There was no risk association with gender or race/ethnicity for gout patients with incident Parkinson’s.
“Gout is associated with a modest increase in the risk of Prkinson’s for adults 65 years or older as a group, independent of other factors,” the researchers wrote, concluding that the “mechanisms of this increased risk of Parkinson’s in patients with gout needs to be investigated further.”
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