title: Secular changes in relative leg length confound height-based spirometric reference values.
abstract: BACKGROUND
  Most but not all data from different ethnic groups fit the Global Lung Function Initiative (GLI) spirometric reference model. This study investigates to what extent discrepancies are caused by secular changes in body proportions.
  
  
  METHODS
  FEV1 and FVC from 20,336 healthy Japanese subjects (13,492 women) aged 17 to 95 years were compared with GLI-2012 reference values for Europeans. Data on the sitting height/standing height ratio (Cormic index) in 17-year-old students, collected from 1949 to 2012 in successive birth cohorts, were used to assess secular changes in body frame. The cohort-specific Cormic index was used to assess how variation in body frame affected pulmonary function.
  
  
  RESULTS
  FEV1 and FVC were lower than GLI-2012 reference values, with values progressively falling until age 35 to 40 years and then rising to European levels in the elderly. The Cormic index rose until 1942, then fell, with a nadir in the 1970s, before rising again until 1995. Nearly one-half of the spirometric variability from predicted values could be explained by differences in the Cormic index between birth cohorts.
  
  
  CONCLUSIONS
  In low-income countries, improving health conditions are likely to drive increases in height and changes in relative leg length similar to those observed in Japan and, thus, to a change in body frame. This implies that height-based prediction equations for such populations will need to be periodically updated.
authors.affiliation: Department of Pulmonary Diseases, Department of Paediatrics, Division of Respiratory Medicine, Erasmus University Medical Centre-Sophia Children's Hospital, Rotterdam, The Netherlands. Electronic address: pquanjer@gmail.com.
authors.forename: Philip H
authors.initials: PH
authors.lastname: Quanjer
authors.affiliation: Department of Respiratory Medicine, School of Medicine, Kitasato University, Kanagawa, Japan.
authors.forename: Masaru
authors.initials: M
authors.lastname: Kubota
authors.affiliation: Graduate School of Medical Sciences, Kitasato University, Kanagawa, Japan.
authors.forename: Hirosuke
authors.initials: H
authors.lastname: Kobayashi
authors.affiliation: Department of Biomedical Laboratory Sciences, Faculty of Life Sciences, Kumamoto University, Kuhonji, Chuo-ku, Kumamoto-shi, Kumamoto, Japan.
authors.forename: Hisamitsu
authors.initials: H
authors.lastname: Omori
authors.affiliation: Department of Respirology, Graduate School of Medicine, Chiba University, Inohana, Chuo-ku, Chiba-shi, Chiba, Japan.
authors.forename: Koichiro
authors.initials: K
authors.lastname: Tatsumi
authors.affiliation: Department of Respiratory Medicine, Saitama Medical University, Morohongo, Moroyama, Iruma-gun, Saitama, Japan.
authors.forename: Minoru
authors.initials: M
authors.lastname: Kanazawa
authors.affiliation: Division of Respiratory Medicine, The Hospital for Sick Children, Institute of Health Policy, Management, and Evaluation, University of Toronto, Toronto, ON, Canada.
authors.forename: Sanja
authors.initials: S
authors.lastname: Stanojevic
authors.affiliation: Respiratory, Critical Care, and Anaesthesia Section (Portex Unit), UCL Institute of Child Health, London, England.
authors.forename: Janet
authors.initials: J
authors.lastname: Stocks
authors.affiliation: Population, Policy and Practice Programme, UCL Institute of Child Health, London, England.
authors.forename: Tim J
authors.initials: TJ
authors.lastname: Cole
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D044466:Asian People; D001827:Body Height / Q000502:physiology*; D005060:Europe; D005260:Female; D005541:Forced Expiratory Volume / Q000502:physiology; D006801:Humans; D007564:Japan; D007866:Leg / Q000033:anatomy & histology*; D008168:Lung / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D008954:Models, Biological; D012016:Reference Values; D012189:Retrospective Studies; D013147:Spirometry / Q000592:standards*; D014797:Vital Capacity / Q000502:physiology; D044465:White People; D055815:Young Adult