title: Incidence of chronic obstructive pulmonary disease, and the relationship between age and smoking in a Japanese population.
abstract: BACKGROUND
  Accurately evaluating a risk of chronic obstructive pulmonary disease (COPD) requires a large-scale longitudinal study using a standard criterion for diagnosing COPD. There have been only a few such follow-up studies in Europe and no reports in Asia. We estimated the incidence rate and incidence rate ratio (IRR) of age and smoking for COPD in a Japanese population using the diagnosis criterion of the Global Initiative for Chronic Obstructive Lung Disease guidelines.
  
  
  METHODS
  Subjects were 17,106 participants aged 25-74 years during health check-ups including spirometry from April 1997 through March 2005 in Japan. Total follow-up of participants were 47,652 person-years in males and 25,224 person-years in females. The IRR of age and smoking was estimated using Cox proportional hazard models with both variables.
  
  
  RESULTS
  We identified 466 incidence cases of COPD. The incidence rate per 100 person-years was 0.81 (95% confidence interval [CI], 0.73-0.89) in males and 0.31 (0.24-0.38) in females, and significantly increased with age in both sexes. The incidence rate for current smokers was significantly higher than that for male non-smokers but not significantly for females. Among males, the IRR for current smokers with Brinkman Index < 400, 400-799, and 800+ was 1.2 (0.8-1.9), 2.7 (1.9-3.8), and 4.6 (3.3-6.5), respectively.
  
  
  CONCLUSIONS
  These results indicated that the COPD risk gradually increased with aging, and that there was a dose-response relationship between smoking and COPD risk.
authors.affiliation: Division of Hygiene, Department of Medicine, Fujita Health University, Aichi, Japan. kojimas@fujita-hu.ac.jp
authors.forename: Shigeko
authors.initials: S
authors.lastname: Kojima
authors.forename: Hiroki
authors.initials: H
authors.lastname: Sakakibara
authors.forename: Shinichi
authors.initials: S
authors.lastname: Motani
authors.forename: Kunihiko
authors.initials: K
authors.lastname: Hirose
authors.forename: Fumio
authors.initials: F
authors.lastname: Mizuno
authors.forename: Masahiro
authors.initials: M
authors.lastname: Ochiai
authors.forename: Shuji
authors.initials: S
authors.lastname: Hashimoto
mesh_terms: D000328:Adult; D000367:Age Factors; D000368:Aged; D005260:Female; D006306:Health Surveys; D006801:Humans; D015994:Incidence; D007564:Japan / Q000453:epidemiology; D008297:Male; D008875:Middle Aged; D029424:Pulmonary Disease, Chronic Obstructive / Q000453:epidemiology* / Q000209:etiology; D012307:Risk Factors; D012907:Smoking / Q000009:adverse effects*; D011795:Surveys and Questionnaires