Background: We have been conducting a cohort study named "the Japan Collaborative Cohort Study (JACC Study) for Evaluation of Cancer Risk sponsored by the Ministry of Education, Science, Sports and Culture of Japan (Monbusho)" since 1988. The aim of this paper is to describe the mortality of our JACC cohort in the follow-up period from 1988 through 1999, to compare it with the mortality, especially cancer deaths, of the Japanese population in the same period and to compare the causes of mortality by district among the cohort. Methods: We conducted a follow-up study of 110,792 Japanese inhabitants aged 40-79 years in 1988-1990 for about 10 years to the end of 1999. Results: Of 46,465 males, 37,750 (81.2%) were alive, 7,238 (15.6%) were dead and 1,477 (3.2%) had moved out of the study areas. The figures were 57,016 (88.6%), 4,940 (7.7%) and 2,371 (3.7%) among 64,327 females, respectively. The mean follow-up period was 9.9 years. The proportion of cancer deaths by site in our cohort members was almost same as the Japanese population aged 40-79 years old in 1995. Sex-specific standardized mortality ratios of total deaths, all cancer deaths, and most cancers in our cohort were less than 100 in both males and females for total cohort and the cohort by district. Conclusion: Our cohort members appeared to be almost the same or slightly healthier and less likely to die from total causes and cancers than the general population.
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