RESUMO
INTRODUCTION: Studies on quality of life in myotonic dystrophy (MD) are scarce and the relationship between respiratory muscle strength and health-related quality of life (HRQoL) has yet to be determined. The present study aims to investigate respiratory muscle strength and HRQoL and their relationship in MD patients. METHODS: Twenty-three patients (13 men, aged 40 ± 16 years) with MD were evaluated for pulmonary function, maximal inspiratory and expiratory pressure (MIP and MEP, respectively), sniff nasal inspiratory pressure (SNIP) and HRQoL using the Short Form (SF-36) quality of life questionnaire. RESULTS: Respiratory muscle strength values were 71 ± 20 cmH2O (64 % predicted), 76 ± 32 cmH2O (70 % predicted), and 79 ± 28 cmH2O (80 % predicted) for MEP, MIP, and SNIP respectively. Significant differences were found in the SF-36 domains of physical functioning 58.7 ± 31.4 vs. 84.5 ± 23 (p < 0.01, 95 % CI = 1.6-39.9) and physical problems 43.4 ± 35.2 vs. 81.2 ± 34 (p < 0.001, 95 % CI = 19.4-6.1) when compared with the reference values. According to single linear regression analysis, MIP explains 29 % of the variance in physical functioning, 18 % of physical problems and 20 % of vitality. CONCLUSIONS: Individuals with MD have reduced expiratory muscle strength. HRQoL may be more impaired in some physical domains, which might be influenced by variations in inspiratory muscle strength.
