Epidemiology of Chronic Airways Diseases in Japan: Changes in Mortality From Lung Diseases
Changes in Mortality From Lung Diseases
Based on official statistics on causes of death, the number of deaths caused by various respiratory diseases within the past 35 years was analyzed. The number of deaths from each disease was expressed as the mean over 5 years. Table 1 shows the death rate from all respiratory diseases per 100,000, and the fraction of all deaths that is attributable to respiratory diseases, expressed in 5-year increments for the years 1951-85. Mortality due to tuberculosis decreased markedly and continually during these 35 years (Fig 2), from a high of 43.5% of all respiratory diseases deaths in 1951-55, to only 5.8% in the past 5 years. Mortality from pneumonia, influenza, or acute respiratory diseases decreased over the first 10-15 years of observation (Fig 3) but has been about 40% (36.3-42.9%) of all respiratory deaths over the 35 years.
Mortality from lung cancer is increasing at an annual rate of 7% or more and is now the second leading cause of death of all respiratory diseases. Mortality from the chronic airways diseases (COPD total in Figure 3; ie, total of ICD code number 490 to 496 since 1978, total of code 490 to 493 and 518 between 1968 to 1977, and code 500 to 502, 241 and 526 before 1967) decreased slightly over 35 years, mainly because of the constant decrease of mortality from bronchial asthma. It accounted for about 18% (15.5-20.6%) of all deaths caused by diseases of the lungs. this
Trends of Mortality From Chronic Airways Disease in Japan
The crude mortality rate from bronchial asthma decreased gradually until 1977, after which it remained almost constant (Fig 4). The crude mortality rate from chronic bronchitis decreased steeply from 1951 to 1960 and increased slightly thereafter. Although the mortality rate from pulmonary emphysema has been reported only since 1968, it has gradually increased to the present. The mortality rate from bronchiectasis has remained almost constant since 1965. As a result, the crude mortality rate from CAD gradually decreased during the first half of the 35 years of study and has remained almost constant during the latter half. No increase in the mortality rate due to CAD was observed from 1960 to 1970 when air pollution was very severe in many industrial areas in Japan.
The age distribution of the Japanese population has changed markedly during these 35 years. In 1951 only 7.7% of the population was aged 60 years or more, but by 1986, 15.3% were in that age group. As the mortality rate from CAD is high in the aged, the age-adjusted mortality rates from these diseases have been decreasing gradually over these 35 years, except emphysema among men (Fig 5).
Age-specific mortality rates for bronchial asthma, chronic bronchitis, and emphysema are shown in Figures 6 to 8. The mortality from bronchial asthma decreased every 5 years in almost all age groups and both sexes. The mortality from chronic bronchitis among men in the age group 50-90 years was almost unchanged during these 35 years, except in 1955. In women a slight decrease of mortality from chronic bronchitis was observed in almost all age groups. The age-specific mortality rate from pulmonary emphysema showed almost no change.
Table 1- Deaths from all Respiratory Diseases in Japan
|Years||Rate/100,000||% all Deaths|
Figure 2. The proportion of various diseases in the total of all deaths from respiratory diseases in Japan, between 1951 and 1985, expressed as mean values for consecutive 5-year periods.
Figure 3. Trends in mortality of various respiratory diseases in Japan, between 1951 and 1985, expressed as mean values for consecutive 5-year periods.
Figure 4. Trends in mortality from chronic airways diseases in Japan from 1951 to 1985.