Abstract
BackgroundAlthough change in the birth cohort effect on cancer mortality rates is known to be highly associated with the decreasing rates of age-standardized cancer mortality rates in Japan, the differences in the trends of cohort effect for representative cancer types among the prefectures remain unknown. This study aimed to investigate the differences in the decreasing rate of cohort effects among the prefectures for representative cancer types using age-period-cohort (APC) analysis.MethodsData on stomach, colorectal, liver, and lung cancer mortality for each prefecture and the population data from 1999 to 2018 were obtained from the Vital Statistics in Japan. Mortality data for individuals aged 50 to 79 years grouped in 5-year increments were used, and corresponding birth cohorts born 1920–1924 through 1964–1978 were used for analysis. We estimated the effects of age, period, and cohort on each type of mortality rate for each prefecture by sex. Then, we calculated the decreasing rates of cohort effects for each prefecture. We also calculated the mortality rate ratio of each prefecture compared with all of Japan for cohorts using the estimates.ResultsAs a result of APC analysis, we found that the decreasing rates of period effects were small and that there was a little difference in the decreasing rates among prefectures for all types of cancer among both sexes. On the other hand, there was a large difference in the decreasing rates of cohort effects for stomach and liver cancer mortality rates among prefectures, particularly for men. For men, the decreasing rates of cohort effects in cohorts born between 1920–1924 and 1964–1978 varied among prefectures, ranging from 4.1 to 84.0% for stomach cancer and from 20.2 to 92.4% for liver cancers, respectively. On the other hand, the differences in the decreasing rates of cohort effects among prefectures for colorectal and lung cancer were relatively smaller.ConclusionsThe decreasing rates of cohort effects for stomach and liver cancer varied widely among prefectures. It is possible that this will influence cancer mortality rates in each prefecture in the future.
Highlights
Change in the birth cohort effect on cancer mortality rates is known to be highly associated with the decreasing rates of age-standardized cancer mortality rates in Japan, the differences in the trends of cohort effect for representative cancer types among the prefectures remain unknown
It is known that age-standardized mortality rates of stomach and liver cancers in particular have decreased in recent years and that these decreases have contributed a decrease in age-standardized mortality rates of all-sites cancer in Japan [2]
The age-standardized mortality rates decreased for all prefectures for stomach and liver cancer, and those for some prefectures increased for colorectal and lung cancer
Summary
Change in the birth cohort effect on cancer mortality rates is known to be highly associated with the decreasing rates of age-standardized cancer mortality rates in Japan, the differences in the trends of cohort effect for representative cancer types among the prefectures remain unknown. Age-standardized mortality rates of all cancer sites have been decreasing in recent years, this decrease in rates is different depending on the type of cancer [1]. Colorectal, liver, pancreatic, and lung cancer were the top 5 causes of cancer mortality in 2018 [1]. It is known that age-standardized mortality rates of stomach and liver cancers in particular have decreased in recent years and that these decreases have contributed a decrease in age-standardized mortality rates of all-sites cancer in Japan [2]. Social burdens associated with cancer mortality rates are large in Japan, and further prevention of cancer is necessary
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