Intellectual Profile in Myotonic Dystrophy Type 1 and Its Association With Its Onset: A Systematic Review and Meta-Analysis

Myotonic dystrophy type 1 (DM1) is caused by mutations in the DMPK gene, and it is associated with cognitive deficits and intelligence below normative values. The objective of this systematic review and meta-analysis was to estimate the overall intelligence and proportion of intellectual development disorder (IDD) in the population with DM1 and its association with its onset. Systematic searches of Medline, Scopus, Web of Science, and Cochrane Library were performed from inception to January 2023. Studies that determined the full intelligence quotient (FIQ) or the IDD proportion in populations with DM1 were included. Meta-analyses of the FIQ and IDD and the FIQ mean difference and IDD prevalence ratios (PRs) by disease onset, inheritance, and genotype were conducted. Forty-five studies were included in the meta-analyses, and all were performed in the DM1 population. The FIQ and IDD in DM1 were 77.90 (71.98, 83.81) and 0.44 (0.27, 0.60), respectively. Furthermore, DM1 onset was negatively associated with intelligence. Thus, the comparison “Congenital versus Adult” onsets resulted in an intelligence quotient of −41.61 (−47.81, −35.40) points and a PR of IDD of 9.49 (3.23, 27.89). Finally, maternal inheritance was also negatively associated, but the genotype did not have a statistically significant association. The alterations in intelligence in DM1 are highly associated with the onset of the disease. However, the genotype did not explain these alterations well and there may be other genetic or epigenetic factors that should be considered.