Analysis of a nationwide study cohort indicated diagnosed depression significantly increased risk for subsequent Parkinson’s disease.
“Depression is more common in patients with Parkinson’s disease than in the general population. It is a major factor for health-related quality of life in patients with [Parkinson’s disease], and may also be associated with more rapid deterioration in cognitive and motor functions,” study researcher Helena Gustafsson, MD, of Umeå University in Sweden, and colleagues wrote in Neurology. “Many studies have reported an increased prevalence of depression in these patients before the clinical onset of [Parkinson’s disease], suggesting that psychological reactions to this disease cannot entirely explain the relationship.”
To evaluate long-term risk for Parkinson’s disease after depression, researchers analyzed data for 3,329,400 Swedish citizens aged 50 years and older as of December 2005, of which 142,460 were diagnosed with depression with no prior diagnosis of Parkinson’s disease. The patients were matched with three controls. After exclusions, the cohort included 140,688 patients with depression and 421,718 matched controls. Study participants had a median age of 62.9 years.
Overall, 0.5% of participants were diagnosed with Parkinson’s disease at a median of 4.5 years after study enrollment. Among the patients with depression, 1.1% were diagnosed with Parkinson’s disease compared with 0.4% of controls.
Conditional logistic regression analysis indicated risk for Parkinson’s disease was higher among participants with depression, however, overall risk decreased from 3.21 (95% CI, 2.5-4.11) within 1 year of enrollment to 1.47 (95% CI, 1.08-2) at 15 to 25 years after enrollment.
Researchers also assessed data from the Swedish Multi-Generation Register for a subcohort of 540,811 sibling pairs to determine familial associations between depression and Parkinson’s disease.
In the sibling cohort, Parkinson’s disease was more common among participants with depression (OR = 1.76; 95% CI, 1.27-2.87). Sibling depression was not associated with risk for Parkinson’s disease (OR = 1.11; 95% CI, 0.91-1.36).
“Our findings suggest a direct association between depression and subsequent [Parkinson’s disease], supported by a time-dependent hazard ratio, a dose-response pattern for recurrent depression, and a lack of evidence for coaggregation among siblings,” Gustafsson and colleagues wrote. “Given that this association was significant over more than 2 decades of follow-up, depression may be a very early prodromal symptoms of or a causal risk factor for [Parkinson’s disease].” – by Amanda Oldt
Disclosure: The researchers report no relevant financial disclosures.