Early weight loss after a diagnosis of Parkinson’s disease (PD) may be a harbinger of more rapid deterioration in cognitive function, new research suggests.

Results showed that in the first year after receiving a PD diagnosis, patients who lost more than 3% of their body weight experienced faster decline in global and executive cognitive function than peers who maintained their weight or gained weight.

Study investigator Jin-Sun Jun, MD, Kangnam Sacred Heart Hospital in Seoul, Korea, noted in a news release that early weight loss is a common nonmotor symptom in PD and “could serve as a sign that people are at risk of cognitive decline.”

The findings were published online October 19 in Neurology.

Weighing the Impact

Both weight loss and weight gain have previously been linked to subsequent dementia in elderly populations. However, the evidence linking early weight change and cognitive decline in PD is lacking, the researchers note.

To investigate further, they assessed 358 adults (66% men; mean age, 61 years) who had been diagnosed with PD an average of 2 years earlier. During the first year after diagnosis, 98 participants lost more than 3% of body weight, 201 maintained their weight (within ±3%), and 59 gained more than 3% of body weight.

Compared with those who maintained their weight, participants who lost weight experienced a significantly faster decline in Montreal Cognitive Assessment (MoCA) scores (β = -0.19; 95% CI, -0.28 to -0.10; P = .001). MoCA measures overall cognitive performance.

In terms of specific cognitive domains, compared with patients who maintained their weight, those who lost weight showed a steeper decline in sematic fluency test scores (β = -0.37; 95% CI, -0.66 to -0.08; P = .01), MoCA phonemic fluency scores (β = -0.18; 95% CI, -0.31 to -0.05; P = .005) and, to a lesser extent, Letter-Number Sequencing scores (β = -0.07; 95% CI, -0.14 to 0.01; P = .07).

Conversely, patients with PD who gained weight demonstrated a slower decline in the Symbol-Digit Modalities Test scores (β = 0.34; 95% CI, 0.05 – 0.63). However, no association was found with longitudinal changes in MoCA scores.

There were no significant effects of weight change on the progression of other nonmotor symptoms.

The researchers note that the findings highlight the potential importance of weight management in the early stages of PD.

Further studies are needed to determine whether taking steps to prevent weight loss could slow cognitive decline in adults with PD, they add.

Cognitive Deconditioning?

Commenting on the findings for Medscape Medical News, Shaheen Lakhan, MD, a neurologist and researcher from Boston, Massachusetts, noted that there are many reasons why weight loss by patients with neurodegenerative diseases such as PD correlates with brain health.

“First, unintentional weight loss may be reflective of poor nutrition status and nutritional deficiencies that directly limit cognitive functioning,” said Lakhan, who was not involved with the research.

He added that it may also represent physical deconditioning, “where body fat is depleted and then muscles atrophy, but also cognitive deconditioning, where the brain as a muscle is less stimulated and neuro-circuits fail.

“This line of research reminds us neurologists to monitor not just the tremor and other movements associated with PD but body measurements like weight and BMI [body mass index] in order to more fully personalize medicine,” Lakhan said.

The study was supported by Hallym University Research Fund 2019. Kim and Lakhan have reported no relevant financial relationships.

Neurology. Published online October 19, 2022. Abstract

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