The study, titled “Cognitive decline over time in adults with myotonic dystrophy type 1: A 9-year longitudinal study,” assessed the cognitive ability of the participants over nine years and is the longest study to date with the largest group of participants.
The team of researchers, led by Dr. Louis Richer of the University of Quebec, assessed the cognitive abilities of 115 DM1 patients looking at their language, memory, visual attention, and processing speed.
They also assessed patients’ ability to organize and manually manipulate spatial information to make a design, known as visuoconstruction, as well as their ability to plan, organize and complete tasks. Researchers also assessed the patients intellectual functioning.
The results showed that there was significant worsening over time in patients’ verbal memory, visual attention, and processing speed. While their executive functions, language, and visual memory declined earlier in adult life, their verbal memory, visual attention, and processing speed declined later.
The decline in patients’ cognitive scores correlated with their age and disease duration. However, the decline in cognitive scores were independent of the number of CTG repeat expansion in their DNA, which is the underlying genetic cause of the disease.
Cognitive decline was also independent of muscular impairment and the patients’ level of education. Intellectual functioning remained stable over time. Finally, the rate of decline was higher among patients who had late-onset DM1.
“These findings on the cognitive evolution in DM1 are highly relevant for clinical practice, as well as for genetic counseling,” the authors wrote, adding that the findings could be used to analyze the effect of potential new treatments for DM1.
DM1 is a genetic condition that affects many organs and systems, including the central nervous system. The cognitive progression of the disease over time, both during the lifespan of a patient and across generations, is a matter of debate among scientists. This study is one of the first to describe the evolution of the cognitive profile of late-onset DM1.