A 9-year follow-up study of the natural progression of upper limb performance in myotonic dystrophy type 1: A similar decline for phenotypes but not for gender

Analysis of the functional capacity outcome measures for myotonic dystrophy

“…Differences between adult‐onset and late‐onset phenotypes have been reported before . In addition, functional performance can differ due to age, gender, and body composition as reported not only in DM1 but also in healthy populations and other neurological disorder .…”

“…For example, after performing this model, walking tests (i.e., 6MWT and 10mWT) significance between male and female disappeared and the difference in 30SSS became significant highlighting the relevant influence of BMI and MIRS in these scores. The late‐onset phenotype subgroup differed significantly from the adult phenotype in all outcomes, which proves once more that generalizability of results should be cautious when considering data from mixed‐phenotypic samples and the association with muscular strength as measured by MIRS . However, using five categories of disease severity (i.e., MIRS) as compared to only two (i.e., Phenotype) was shown to be more strongly associated with patient performance.…”

“…Even though this is a progressive disease and it would be unlikely to detect improvement when there has been no intervention, we cannot accept or reject these findings as multiple factors could influence on muscle strength scoring from T1 to T2. Other studies that have investigated natural disease progression in DM1 over a longer period of time, identified differences in speed and magnitude of disease progression between the late onset and the adult phenotype. These differences were not detected at our 1‐year study.…”

“…The inclusion criteria were: a genetically confirmed diagnosis of DM1; ≥18 years; ability to provide informed consent and walk independently (assistive devices and orthotics allowed) for at least 10 m. The cohort recruited at one of the study sites (Newcastle) was followed up for 1 year as part of the longitudinal analysis. Patients were classified as late onset if they met two of the three following criteria: (1) first symptoms reported at the age of ≥40 years; (2) ≤200 CTG repeats; and (3) a MIRS score of I or II; otherwise they were categorized as adult (classic) phenotype . Participants with an early adult (juvenile) phenotype (i.e., first symptoms reported before 20 years old) were included in the adult phenotype group.…”

Responsiveness of performance-based outcome measures for mobility, balance, muscle strength and manual dexterity in adults with myotonic dystrophy type 1

“…Adults with a genetically DNA-confirmed diagnosis of DM1 and presenting with the adult-onset or late-onset phenotype were recruited from the Saguenay Neuromuscular Clinic (Quebec, Canada). As part of a funded longitudinal study, 200 patients with DM1 were included at baseline (T1) (8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18) and were invited to attend a follow-up 9 years later (T2) (19)(20). At T2 59 of the 200 patients had died, 8 had left the region, 4 were excluded due to severe cognitive impairment, and 14 declined to participate (for personal reasons or lack of interest).…”