Overweight Is an Independent Risk Factor for Reduced Lung Volumes in Myotonic Dystrophy Type 1

• Published in: PloS one 2016-03, Vol.11 (3), p.e0152344-e0152344
• Main Authors: Seijger, Charlotte G W, Drost, Gea, Posma, Joram M, van Engelen, Baziel G M, Heijdra, Yvonne F
• Format: Article
• Language: English
• Subjects: Adult; Aged; Analysis; Biology and Life Sciences; Body composition; Body mass; Body Mass Index; Body size; Body weight; Chronic obstructive pulmonary disease; Dystrophy; Expiratory Reserve Volume - physiology; Fat-free body mass; Female; Humans; Kinases; Linear Models; Lungs; Male; Medicine and Health Sciences; Middle Aged; Muscle strength; Myotonic dystrophy; Myotonic Dystrophy - diagnosis; Myotonic Dystrophy - etiology; Myotonic Dystrophy - physiopathology; Obesity; Overweight; Overweight - complications; Overweight - diagnosis; Overweight - physiopathology; Patients; Physical Sciences; Population studies; Pulmonary function tests; Pulmonary functions; Research and Analysis Methods; Respiration; Respiratory function; Respiratory Function Tests; Risk Factors; Studies; Total Lung Capacity - physiology
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0152344

In this large observational study population of 105 myotonic dystrophy type 1 (DM1) patients, we investigate whether bodyweight is a contributor of total lung capacity (TLC) independent of the impaired inspiratory muscle strength. Body composition was assessed using the combination of body mass index (BMI) and fat-free mass index. Pulmonary function tests and respiratory muscle strength measurements were performed on the same day. Patients were stratified into normal (BMI < 25 kg/m(2)) and overweight (BMI ≥ 25 kg/m(2)) groups. Multiple linear regression was used to find significant contributors for TLC. Overweight was present in 59% of patients, and body composition was abnormal in almost all patients. In overweight patients, TLC was significantly (p = 2.40×10(-3)) decreased, compared with normal-weight patients, while inspiratory muscle strength was similar in both groups. The decrease in TLC in overweight patients was mainly due to a decrease in expiratory reserve volume (ERV) further illustrated by a highly significant (p = 1.33×10(-10)) correlation between BMI and ERV. Multiple linear regression showed that TLC can be predicted using only BMI and the forced inspiratory volume in 1 second, as these were the only significant contributors. This study shows that, in DM1 patients, overweight further reduces lung volumes, as does impaired inspiratory muscle strength. Additionally, body composition is abnormal in almost all DM1 patients.