May 24, 2021
Depression and psychosis are significantly associated with neuronal loss and gliosis – but not with Lewy body scores – in Parkinson's disease, data from analyses of the brains of 175 patients suggest.
Previous research has suggested a link between neuronal loss and depression in Parkinson's disease (PD) but the impact of Lewy bodies has not been well studied, Nicole Mercado Fischer, MPH, of Johns Hopkins University, Baltimore, and colleagues wrote.
Evaluating Lewy body scores and neuronal loss/gliosis in the substantia nigra pars compacta (SN) and locus coeruleus (LC) could increase understanding of pathophysiology in PD, they said.
In a study published in the American Journal of Geriatric Psychiatry, the researchers analyzed the brains of 175 individuals with a primary diagnosis of PD.
A total of 98 participants had diagnoses of psychosis, 88 had depression, and 55 had anxiety. The average age of onset for PD was 62.4 years; 67.4% of the subjects were male, and 97.8% were White. The mean duration of illness was 16 years, and the average age at death was 78 years.
Psychosis was significantly associated with severe neuronal loss and gliosis in both the LC and SN (P = .048 and P = .042, respectively). Depression was significantly associated with severe neuronal loss in the SN (P = .042) but not in the LC. Anxiety was not associated with severe neuronal loss in either brain region. These results remained significant after a multivariate analysis, the researchers noted. However, Lewy body scores were not associated with any neuropsychiatric symptom, and severity of neuronal loss and gliosis was not correlated with Lewy body scores.
The study findings were limited by several factors, including the retrospective design and inability to collect pathology data for all patients, the researchers noted. Also, in some cases, the collection of clinical data and observation of brain tissue pathology took place years apart, and the researchers did not assess medication records.
However, the results were strengthened by the large sample size and "further support the notion that in vivo clinical symptoms of PD are either not caused by Lewy body pathology or that the relationship is confounded by the time of autopsy," they said. Future directions for research include examining the underlying neuropsychiatric symptoms in PD "by looking at pathology in functional subregions and eventually by using new functional imaging techniques in vivo."
The researchers had no financial conflicts to disclose. Two coauthors were supported in part by the National Institutes of Health.