Respiratory muscle strength and quality of life in myotonic dystrophy patients

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 cmH(2)O (64% predicted), 76 +/- 32 cmH(2)O (70% predicted), and 79 +/- 28 cmH(2)O (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. (c) 2010 Published by Elsevier Espana, S.L. on behalf of Sociedade Portuguesa de Pneumologia. All rights reserved.