Long-term trends of liver cancer mortality by gender in urban and rural areas in China: an age-period-cohort analysis

OBJECTIVES To provide an up-to-date overview of long-term trends of liver cancer mortality and evaluate the effects attributable to age, period and cohort in Chinese population stratified by gender and urban/rural areas. METHODS Population and liver cancer mortality data were obtained based on the Disease Surveillance Points in China from 1991 to 2014. To examine the time trends of liver cancer mortality by gender in urban and rural areas in China, Joinpoint analysis was used to estimate the annual per cent change. The intrinsic estimator, a method of age-period-cohort analysis to estimate age, period and cohort effects simultaneously, was used to analyse the underlying mechanisms for liver cancer mortality trends in the aforementioned four groups. RESULTS We observed a significant decline in liver cancer mortality for urban men (average annual per cent change (AAPC)=-1.1%, P<0.05) and urban women (AAPC=-1.4%, P<0.05), while the liver cancer mortality remained stable for rural men (AAPC=-0.1%, P>0.05) and rural women (AAPC=-0.9%, P>0.05). Compared with the 15-19 age group, the liver cancer mortality risk of the 85 and above age group increased 65 and 42 times for urban and rural men, and 102 and 70 times for urban and rural women. From the 1990-1994 period to the 2005-2009 period, the risk increased 56% and 92% for urban and rural men, and 30% and 74% for urban and rural women. Compared with period and cohort effects, age effects were the most influential factor in liver cancer mortality. CONCLUSIONS As the status of ageing population in China gets worse, the burden caused by liver cancer mortality could still be a great challenge for China in the future. The disparity of liver cancer mortality trends between urban and rural residents can be attributed to period effects, referring to the unequal medical levels and resources between urban and rural areas.