Prospective measurement of quality of life in myotonic dystrophy type 1
Myotonic dystrophy type 1 (DM1) is the most common muscular dystrophy in adults.1 Muscle weakness in neuromuscular disorders affects motor efficiency, causes disability, increases risk of secondary disorders, and may severely diminish quality of life (QoL).2 DM1 is a multisystem disorder which also has impaired QoL that worsens with a longer duration of disease symptoms.2 Generic patient reported outcome measures have had varied and limited success in tracking QoL in DM1. One study showed a decrease of QoL in DM patients in a 5‐year period using the Sickness Impact Profile.5 In another cohort of DM1 patients, QoL measured by SF‐36 questionnaire showed paradoxical improvement during a 5‐year period despite progression of muscle weakness.6 The Individualized Neuromuscular Quality of Life questionnaire (INQoL) is an instrument initially validated using patients with a variety of neuromuscular diseases.7 The INQoL may have advantages in DM1 over generic patient reported outcome measures. Results from a prior study suggest that the INQoL is more capable of capturing pain symptoms in DM1 patients than the bodily pain domain of the SF‐36.9 INQoL was developed in the UK, and later used in Italy, Serbia, the Netherlands, USA, Japan, France, Germany, and Spain.10 It has been applied in several muscle disease studies including myotonic dystrophy.10 However, the responsiveness of this instrument in DM1 has yet to be defined.
The aim of this study was to analyze changes of INQoL scores in patients with DM1 during a 6‐year clinic follow‐up period.