Current epidemiological trend of tuberculosis in Japan

OBJECTIVE: To observe the recent epidemiological trend of tuberculosis and to determine the factors related to the deteriorating trend in incidence and mortality rates in Japan.

DESIGN: Descriptive analyses of tuberculosis notification rates and mortality rates by age, sex, year and birth-cohort.

RESULTS: The decline in the tuberculosis notification rate has started slowing down since around 1980. Among the cohorts born before 1950, the trend of notification rate by age has levelled off since around 1980. The reduction in the tuberculosis mortality rate has also recently begun to slow down, but later and to a lesser extent than that of the notification rate. Although deaths due to tuberculosis occur mostly among the elderly, the rate of decline in mortality among middle-aged males has slowed down recently. The trend in the mortality rate of birth-cohorts has recently shown an upward trend with age.

CONCLUSION: A major cause of the current stagnation of the decline in notification rates is the increase in the elderly population with a high prevalence of tuberculosis infection in the past, who are more likely to develop the disease as they approach biological senescence. Other possible causes are a gradual shift of the tuberculosis problem to socio-economically deprived segments of the urban population, and behavioural changes causing delay in case-finding.