Mortality trends of bladder cancer in China from 1991 to 2015: an age-period-cohort analysis

Purpose: The effects of age, period, and cohort on mortality rates of bladder cancer in China remained vague. This study aimed to analyze the secular trends of bladder cancer mortality in China and estimate the independent effects of age, period, and cohort. Methods: Data for bladder cancer mortality from 1991 to 2015 was obtained from the WHO Mortality Database and China Health Statistical Yearbook. The age-period-cohort model was used to estimate the effect of age, period, and cohort. The intrinsic estimator method was used to solve the nonidentification problem of collinearity among age, period, and cohort. Results: The age-standardized mortality rates of total residents (2.33-1.87/100,000), male (3.45-2.89/100,000), and female (1.24-0.82/100,000) showed decreasing trends, which was more obvious in males than in females. Age effects increased consistently with age in all age groups (coefficients: -2.02 to 1.91 in the total population, -2.06 to 2.02 in males and -2.04 to 1.81 in females). Cohort effects decreased overall (coefficients: 0.96 to -1.62 in the total population, 1.11 to -1.66 in males and 0.78 to -1.46 in females). Period effects were not found in China. Conclusion: Although a decreasing mortality was observed, the bladder cancer burden in China will likely increase in the next few years due to population aging, environmental pollution, and food safety. The findings suggested that preventive measures should be taken corresponding to the changes in age-and cohort-related factors in the population.