Weight Loss Early in Parkinson’s Linked to Faster Cognitive Decline
New findings may highlight importance of weight management in Parkinson's
Weight loss within the first years of a Parkinson’s disease diagnosis is linked to a faster decline in global cognitive function over time, a new study found. Conversely, early weight gain was associated with slower deterioration of attention and processing speed in these patients.
The study results add to increasing evidence that points to a link between weight loss and faster progression of motor and non-motor symptoms in Parkinson’s.
“These findings highlight the potential importance of weight management in the early stages of Parkinson’s disease,” Jin-Sun Jun, MD, one of the study’s authors, from the Kangnam Sacred Heart Hospital, in South Korea, said in a press release.
“Early weight loss is a common symptom in people with Parkinson’s disease,” and “it could serve as a sign that people are at risk of cognitive decline,” Jun said.
Future research is needed to confirm these findings and assess whether interventions to prevent weight loss may help preserve cognitive function in this patient population, according to the team.
Weight loss in early Parkinson’s
The study, “Association of Early Weight Change With Cognitive Decline in Patients With Parkinson Disease,” was published in the journal Neurology.
Parkinson’s disease, characterized by the death and dysfunction of specific nerve cells in the brain, leads to a progressive loss of coordination and movement problems. But it also can cause non-motor symptoms such as cognitive impairment, depression, sleep problems, and hallucinations.
Although weight loss is common among patients with early Parkinson’s, the reasons for it are not fully understood. Previous studies have shown that early weight loss predicts poor outcomes. However, its impact on cognitive function remains largely unclear.
To address this, Jun and colleagues in Seoul analyzed data from 358 Parkinson’s patients who were enrolled in the Parkinson’s Progression Markers Initiative (PPMI). The PPMI, a clinical study launched by The Michael J. Fox Foundation for Parkinson’s Research in 2010, seeks to identify biomarkers of the disease’s onset and progression.
The patients had a mean age of 61. All were diagnosed within two years of PPMI entry and had not started taking medications for the disease. They were followed for up to eight years, completing annual non-motor assessments such as cognitive function tests.
One of these tests was the Montreal Cognitive Assessment (MoCA), which comprises five cognitive domains — attention/working memory, episodic memory, language, visuospatial, and executive function. Executive function encompasses a set of skills such as working memory, flexible thinking, and self-control that help in everyday life in completing differing tasks.
Scores range from zero to 30, with higher values indicating better cognitive function.
Patients were split into three groups according to whether their weight changed by more than 3% of body weight and to which direction (loss or gain). A majority of patients — 201 or 56.1% — experienced no changes in weight during this period. Meanwhile, 98 people (27.4%) showed weight loss and 59 (16.5%) experienced weight gain.
Results showed that overall cognitive function, as assessed with the MoCA, declined significantly faster (by 0.19 points) among patients experiencing early weight loss than it did among those in the stable weight group. At study’s start, both groups had MoCA scores of 27, indicating normal cognitive function, the researchers noted.
With respect to specific cognitive domains, the weight loss group showed a steeper decline in verbal fluency skills — a measure of executive function — than the weight maintenance group, as assessed with both MoCA and other cognitive tests.
While no link was found between early weight gain and changes in total MoCA scores over time, patients in the weight gain group showed a slower decline in processing speed and attention. Cognitive processing speed is the amount of time it takes a person to take in information, process it, and then react to solve a problem or complete a task.
Notably, when looking at data from 174 people without Parkinson’s, the researchers found no such links between weight change and scores of cognitive function tests.
In addition, the team “did not find any significant effects of weight change on the progression of other non-motor symptoms.”
“The impact of early weight change on non-motor symptoms appeared to be specific to cognition,” the researchers wrote.
These findings highlight that “early weight loss was associated with a faster progression of decline in global cognitive function and executive function in [Parkinson’s disease] patients, whereas early weight gain was associated with a slower progression of decline in processing speed and attention,” the team wrote.
Among the study’s limitations, the investigators emphasized their inability to determine if observed weight changes were intentional or not, and whether weight change had different effects on cognition in underweight versus obese patients.
“Further studies are needed to determine whether taking steps to prevent weight loss could slow cognitive decline in people with Parkinson’s,” Jun said.