With over 10 million sufferers across the world, Parkinson's disease (PD) is among the worst neurodegenerative diseases affecting mankind. It is characterised by a steady deterioration in motor and cognitive skills, which ultimately affects one's quality of life. Shedding new light on the progression of this debilitating condition, scientists have found an association between changes in weight among PD patients and a decline in their cognitive skills.
According to a new South Korean study, individuals who lose weight shortly after being diagnosed with PD are more likely to experience a faster decline in their cognitive skills when compared to those who maintained their weight. In contrast, early weight gain in patients was associated with a slower decline in attention and processing speed.
"Early weight loss is a common symptom in people with Parkinson's disease. It could serve as a sign that people are at risk of cognitive decline," said Dr. Jin-Sun Jun, corresponding author of the study, in a statement. The findings were published in the journal American Academy of Neurology.
Exploring An Association
For the observational study, the team enrolled 358 individuals (average age=61) who had been diagnosed with PD two years prior to the commencement of the research and had not commenced treatment with PD medications. These patients were compared to healthy individuals (n=174) without PD
Next, the researchers defined the change in the enrolees' body weight in order to classify them into different groups. While weight loss or gain was described as a change of over 3 percent of body weight in the first year of the study, weight maintenance was defined as a change of less than 3 percent of body weight or no change at all. Based on these definitions, the participants were categorized into three groups: weight loss (n=98), weight gain (n=59), and weight maintenance (n=201).
The participants were subjected to annual assessments—from the beginning of the study to up to eight years of follow-up—associated with autonomic, sleep-related, and neuropsychiatric symptoms. Their cognitive functions were evaluated through extensive neuropsychological testing and using the Montreal Cognitive Assessment (MoCA), a cognitive screening test.
Change in Weight and Cognitive Decline
Through their analysis, the authors made an interesting observation: there was a quicker decline in the overall cognitive scores among patients in the weight loss group when compared to those in the weight maintenance group. While both groups began with average scores of 27, there was a comparatively faster decline of 0.19 points per year among patients who had lost weight. The skills that displayed the sharpest decline were associated with verbal fluency, a determinant in the measurement of executive function.
Conversely, in comparison to participants in the weight maintenance group, those in the weight gain group showed a slower decline when it came to scores on tests measuring processing speed and attention. No association was found between a change in weight and other non-motor symptoms. Also, no connection was found between weight change and cognitive skill scores among healthy individuals.
"These findings highlight the potential importance of weight management in the early stages of Parkinson's disease. Further studies are needed to determine whether taking steps to prevent weight loss could slow cognitive decline in people with Parkinson's," stated Dr. Jun.
The researchers, however, admitted that the study was bound by a few limitations. Firstly, it only shows a link between weight change and cognitive skills, it does not prove it. Secondly, it did not examine whether cognitive skills were affected by changes in weight among Parkinson's patients who were underweight or obese. Finally, they had not ascertained whether the weight change in patients was unintentional or intentional.
