Subjective symptom impact on quality of life in patients with myotonic dystrophy

Abstract Background: Although functional impairment in patients with myotonic dystrophy is an important determinant of quality of life (QoL), it is possible that QoL could further be influenced by the subjective evaluation of symptoms. The aim of this study was to investigate the subjective symptom impact on the QoL, after controlling for functional impairment. Methods: Eligible patients with myotonic dystrophy type 1 (DM1) were recruited from four hospitals in Japan. Subjective symptom impact across four domains (muscle weakness, fatigue, pain, and myotonia) and overall QoL were evaluated using the Individualized Neuromuscular Quality of Life (INQoL) questionnaire. Functional impairment was assessed using the modified Rankin scale. Results: Eighty-six patients with DM1 were included in this study. On multiple regression analysis, a portion of the variance in the overall QoL was significantly accounted for by demographic variables and functional impairment (adjusted R2 = 0.32). In addition to these variables, subjective symptom impact (muscular weakness, fatigue, and myotonia) explained additional variance in the overall QoL (adjusted R2 = 0.80). Difficulties in activities of daily living and participation caused by each symptom consistently predicted overall QoL across three symptom domains (muscular weakness, fatigue, and myotonia). Conclusions: Subjective symptom impact needs to be considered, in addition to functional impairment, when evaluating the QoL of patients with DM1.