Faster Progression Found in ‘Body-involvement’ Parkinson’s in Study
Findings may support 2 patient subgroups based on nervous system effects
People with Parkinson’s disease who show early dysfunction in the nerves controlling heartbeat tend to experience faster disease progression, a new study shows.
According to researchers, these results support a new approach differentiating “brain-predominant” Parkinson’s from disease with “body-involvement.”
“These findings correspond well to the results of [an] earlier study that classified brain-first and body-first [Parkinson’s disease],” the team wrote, noting that patients with body involvement “had more severe symptoms and steeper motor deterioration.”
Parkinson’s is characterized by the death and dysfunction of dopamine-producing cells in the brain, but the biological mechanisms underlying the disease remain obscure. In recent years, some scientists have proposed that it may be possible to divide Parkinson’s patients into subgroups based on patterns of how the nervous system is affected.
‘Brain-predominant’ versus ‘body-involvement’
Specifically, some researchers think that Parkinson’s can be divided into two types: brain-predominant Parkinson’s, or br-PD, in which the damage is mostly limited to cells in the brain, or Parkinson’s with body-involvement, called bo-PD, where nerves throughout the body also are affected early in the disease course. In bo-PD, the peripheral nervous system is affected, according to these scientists.
Now, a team of scientists at the Catholic University of Korea tested whether patients classified as br-PD or bo-PD showed differences in terms of clinical outcomes, specifically Parkinson’s progression.
The study included data on 132 Parkinson’s patients, ages to 50 to 75, who were divided into the subtypes based on whether they showed signs of dysfunction in the nerves that control heart rate. This was measured with an imaging technique called 123I-MIBG scintigraphy.
The 103 patients with signs of this cardiac nerve dysfunction on their first evaluation were classified as bo-PD, while the remaining 29 without symptoms of dysfunction on initial evaluation were labeled br-PD. The age at Parkinson’s onset, sex distribution, and educational status were comparable between the two groups, as were rates of high blood pressure and diabetes, though disease duration was longer in the br-PD group.
Motor symptoms, measured with the Unified Parkinson’s Disease Rating Scale (UPRDS) part III, were significantly worse in the bo-PD group compared with the br-PD group at the study’s start, though tremor severity was comparable in both groups. Over time, motor symptoms worsened more quickly in the bo-PD group than the br-PD group.
“Motor symptoms were more severe at the initial presentation in the bo-PD group. In addition, motor symptoms deteriorated more steeply in the bo-PD phenotype than in the br-PD phenotype,” the researchers wrote.
Overall cognitive measures were generally similar between the groups both at the study’s start and over follow-up, though the bo-PD group scored worse on memory tests initially. The researchers noted that while both groups showed decline over time in measures of cognition related to language, other specific cognitive changes varied by group: patients with bo-PD more commonly had issues with attention and working memory, while those with br-PD were more likely to have executive function challenges.
At the study’s start, rates of depression, urinary dysfunction, and unspecified pain were similar in both groups. However, rates of rapid-eye-movement sleep behavior disorder (RBD), excessive daytime sleepiness, constipation, and orthostatic hypotension (when blood pressure drops upon standing) were significantly higher in the bo-PD group.
“The two groups in our study showed a different frequency in non-motor manifestations” of Parkinson’s, the researchers wrote. They concluded that, overall, “the bo-PD subtype is more aggressive phenotype than the br-PD subtype.”
A noted limitation of this study is that the follow-up times were not standardized and varied from patient to patient. The researchers also stressed that this study focused specifically on individuals in the earliest stages of diagnosed Parkinson’s.