A Seoul National University Bundang Hospital (SNUBH) research team has found that key cognitive functions such as memory and attention gradually decline in patients with idiopathic REM (rapid eye movement) sleep behavior disorder even before the condition progresses to overt neurodegenerative disease.
,_홍정경_교수(우).jpg)
A SNUBH team, led by Professors Yoon In-young (left) and Hong Jung-kyung, confirmed that patients with idiopathic REM sleep behavior disorder experience gradual cognitive decline over long-term follow-up even before progression to neurodegenerative diseases. (Credit: SNUBH)
The team, led by Professors Yoon In-young and Hong Jung-kyung of the Department of Psychiatry at SNUBH, tracked 162 patients with idiopathic REM sleep behavior disorder for an average of 7.7 years.
REM sleep behavior disorder involves physically acting out dreams, with symptoms such as shouting, punching, or kicking during sleep.
The condition is known as a prodrome to neurodegenerative diseases like Parkinson's disease or dementia, and it is diagnosed as idiopathic REM sleep behavior disorder when no other neurological causes are present.
While the disorder is closely linked to neurodegenerative diseases, long-term studies on cognitive changes in these patients have been scarce because previous studies often involved small groups tracked for a short period of time like two to four years.
The study focused on 162 patients who maintained an idiopathic REM sleep behavior disorder status for at least five years before progression to overt neurodegenerative disease.
Based on a total of 318 neuropsychological evaluations, the team analyzed cognitive function across five areas, including attention and working memory, memory, executive function, visuospatial function, and language function.
Test results were converted into z-scores which indicate how far a patient deviates from the average of a group with the same age, gender, and education level.
A z-score of minus 1.5 or lower is considered a significant cognitive decline.
The analysis showed that patients experienced gradual but consistent declines in attention, working memory, and memory.
The digit symbol test which measures processing speed and visual motor coordination showed the most rapid decline with an average annual z-score decrease of 0.084. The test was identified as the most sensitive indicator for detecting early cognitive changes in the study.
Memory tests also showed steady annual declines of 0.054 in verbal memory and 0.037 in visual memory. The researchers explained that while these changes might be difficult to perceive in the short term, they can reach clinically significant levels when accumulated over a long period.
Gender analysis revealed that 116 male patients showed extensive decline across various domains. In contrast, 46 female patients showed limited decline in only two items including the digit span forward and digit symbol tests.
“Female patients may have higher resilience to brain damage or a slower rate of abnormal protein accumulation in the brain,” Yoon said. “Gender specific monitoring strategies and customized management are necessary.”
The team also analyzed 33 longstanding idiopathic REM sleep behavior disorder patients who did not present overt neurodegenerative diseases for more than ten years.
These patients showed cognitive decline similar to or, in some tests, even steeper than the overall patient group.
The finding contradicts the hypothesis that longstanding patients would experience slower neurodegeneration. It suggests that even patients who maintain idiopathic REM sleep behavior disorder for a long time may be undergoing gradual neurodegenerative changes, necessitating regular cognitive evaluations.
“The research clearly demonstrates that cognitive decline can occur in patients with idiopathic REM sleep behavior disorder even before progression to neurodegenerative disease,” Hong said. “Individuals with the disorder should receive regular examinations and medical follow ups even if they do not exhibit symptoms of dementia or Parkinson disease.”
The findings were published in the international journal Sleep.
Source: https://www.koreabiomed.com/news/articleView.html?idxno=30658
