title: Overweight Is an Independent Risk Factor for Reduced Lung Volumes in Myotonic Dystrophy Type 1.
abstract: BACKGROUND
  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.
  
  
  METHODS
  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.
  
  
  RESULTS
  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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Department of Pulmonary diseases, Radboud University Medical Center, Nijmegen, the Netherlands.
authors.forename: Charlotte G W
authors.initials: CG
authors.lastname: Seijger
authors.affiliation: Department of Neurology, Department of Neurosurgery, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands.
authors.forename: Gea
authors.initials: G
authors.lastname: Drost
authors.affiliation: Division of Computational and Systems Medicine, Department of Surgery and Cancer, Faculty of Medicine, South Kensington Campus, Imperial College London, London, United Kingdom.|Department of Epidemiology and Biostatistics, School of Public Health, Faculty of Medicine, St. Mary's Campus, Imperial College London, London, United Kingdom.
authors.forename: Joram M
authors.initials: JM
authors.lastname: Posma
authors.affiliation: Neuromuscular Center Nijmegen, Institute of Neurology, Radboud University Medical Center, Nijmegen, The Netherlands.
authors.forename: Baziel G M
authors.initials: BG
authors.lastname: van Engelen
authors.affiliation: Department of Pulmonary diseases, Radboud University Medical Center, Nijmegen, the Netherlands.
authors.forename: Yvonne F
authors.initials: YF
authors.lastname: Heijdra
mesh_terms: D000328:Adult; D000368:Aged; D015992:Body Mass Index; D005105:Expiratory Reserve Volume / Q000502:physiology; D005260:Female; D006801:Humans; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D009223:Myotonic Dystrophy / Q000175:diagnosis / Q000209:etiology / Q000503:physiopathology*; D050177:Overweight / Q000150:complications / Q000175:diagnosis / Q000503:physiopathology*; D012129:Respiratory Function Tests; D012307:Risk Factors; D014109:Total Lung Capacity / Q000502:physiology*