Age-Period-Cohort Analysis of Chronic Obstructive Pulmonary Disease Mortality in Japan, 1950–2004

BACKGROUND: We examined trends in chronic obstructive pulmonary disease (COPD) mortality in Japan. METHODS: An age-period-cohort model was used to examine trends in COPD mortality by age, time period, and birth cohort among adults aged 40 years or older from 1950 to 2004. RESULTS: During the study period, the age-standardized rate of COPD mortality substantially decreased from 71.3 per 100 000 to 19.7 in men and from 41.7 to 4.3 in women. The period effects rapidly declined during the early period in both sexes. They have increased in recent years in men but have continued to decrease in women. The cohort effects began increasing in the 1865–1869 birth cohort, peaked in the 1880–1889 cohort, and decreased thereafter among the recent cohorts. CONCLUSIONS: An early decrease in the period effects might have been associated with changes in disease structure and misclassification of COPD in the early period. Changes in cohort effects might have been mostly associated with changes in cigarette consumption and smoking prevalence in the Japanese population. Changes in those effects may also be a proxy for other social changes over time.