title: Lung function in young adults predicts airflow obstruction 20 years later.
abstract: OBJECTIVE
  The burden of obstructive lung disease is increasing, yet there are limited data on its natural history in young adults. To determine in a prospective cohort of generally healthy young adults the influence of early adult lung function on the presence of airflow obstruction in middle age.
  
  
  METHODS
  A longitudinal study was performed of 2496 adults who were 18 to 30 years of age at entry, did not report having asthma, and returned at year 20. Airflow obstruction was defined as an forced expiratory volume in 1 second/forced vital capacity ratio less than the lower limit of normal.
  
  
  RESULTS
  Airflow obstruction was present in 6.9% and 7.8% of participants at years 0 and 20, respectively. Less than 10% of participants with airflow obstruction self-reported chronic obstructive pulmonary disease. In cross-sectional analyses, airflow obstruction was associated with less education, smoking, and self-reported chronic obstructive pulmonary disease. Low forced expiratory volume in 1 second, forced expiratory volume in 1 second/forced vital capacity ratio, and airflow obstruction in young adults were associated with low lung function and airflow obstruction 20 years later. Of those with airflow obstruction at year 0, 52% had airflow obstruction 20 years later. The forced expiratory volume in 1 second/forced vital capacity at year 0 was highly predictive of airflow obstruction 20 years later (c-statistic 0.91; 95% confidence interval, 0.89-0.93). The effect of cigarette smoking on lung function decline with age was most evident in young adults with preexisting airflow obstruction.
  
  
  CONCLUSIONS
  Airflow obstruction is mostly unrecognized in young and middle-aged adults. Low forced expiratory volume in 1 second, low forced expiratory volume in 1 second/forced vital capacity ratio, airflow obstruction in young adults, and smoking are highly predictive of low lung function and airflow obstruction in middle age.
authors.affiliation: Northwestern University, Chicago, IL 60611, USA.
authors.forename: Ravi
authors.initials: R
authors.lastname: Kalhan
authors.forename: Alexander
authors.initials: A
authors.lastname: Arynchyn
authors.forename: Laura A
authors.initials: LA
authors.lastname: Colangelo
authors.forename: Mark T
authors.initials: MT
authors.lastname: Dransfield
authors.forename: Lynn B
authors.initials: LB
authors.lastname: Gerald
authors.forename: Lewis J
authors.initials: LJ
authors.lastname: Smith
mesh_terms: D000293:Adolescent; D000328:Adult; D005260:Female; D005541:Forced Expiratory Volume; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D029424:Pulmonary Disease, Chronic Obstructive / Q000175:diagnosis*; D012907:Smoking / Q000009:adverse effects; D013997:Time Factors; D014797:Vital Capacity
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