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      Impact of smoking on mortality and life expectancy in Japanese smokers: a prospective cohort study

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          Abstract

          Objective To investigate the impact of smoking on overall mortality and life expectancy in a large Japanese population, including some who smoked throughout adult life.

          Design The Life Span Study, a population-based prospective study, initiated in 1950.

          Setting Hiroshima and Nagasaki, Japan.

          Participants Smoking status for 27 311 men and 40 662 women was obtained during 1963-92. Mortality from one year after first ascertainment of smoking status until 1 January 2008 has been analysed.

          Main outcome measures Mortality from all causes in current, former, and never smokers.

          Results Smokers born in later decades tended to smoke more cigarettes per day than those born earlier, and to have started smoking at a younger age. Among those born during 1920-45 (median 1933) and who started smoking before age 20 years, men smoked on average 23 cigarettes/day, while women smoked 17 cigarettes/day, and, for those who continued smoking, overall mortality was more than doubled in both sexes (rate ratios versus never smokers: men 2.21 (95% confidence interval 1.97 to 2.48), women 2.61 (1.98 to 3.44)) and life expectancy was reduced by almost a decade (8 years for men, 10 years for women). Those who stopped smoking before age 35 avoided almost all of the excess risk among continuing smokers, while those who stopped smoking before age 45 avoided most of it.

          Conclusions The lower smoking related hazards reported previously in Japan may have been due to earlier birth cohorts starting to smoke when older and smoking fewer cigarettes per day. In Japan, as elsewhere, those who start smoking in early adult life and continue smoking lose on average about a decade of life. Much of the risk can, however, be avoided by giving up smoking before age 35, and preferably well before age 35.

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          Most cited references17

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          Studies of the mortality of atomic bomb survivors, Report 14, 1950-2003: an overview of cancer and noncancer diseases.

          This is the 14th report in a series of periodic general reports on mortality in the Life Span Study (LSS) cohort of atomic bomb survivors followed by the Radiation Effects Research Foundation to investigate the late health effects of the radiation from the atomic bombs. During the period 1950-2003, 58% of the 86,611 LSS cohort members with DS02 dose estimates have died. The 6 years of additional follow-up since the previous report provide substantially more information at longer periods after radiation exposure (17% more cancer deaths), especially among those under age 10 at exposure (58% more deaths). Poisson regression methods were used to investigate the magnitude of the radiation-associated risks, the shape of the dose response, and effect modification by gender, age at exposure, and attained age. The risk of all causes of death was positively associated with radiation dose. Importantly, for solid cancers the additive radiation risk (i.e., excess cancer cases per 10(4) person-years per Gy) continues to increase throughout life with a linear dose-response relationship. The sex-averaged excess relative risk per Gy was 0.42 [95% confidence interval (CI): 0.32, 0.53] for all solid cancer at age 70 years after exposure at age 30 based on a linear model. The risk increased by about 29% per decade decrease in age at exposure (95% CI: 17%, 41%). The estimated lowest dose range with a significant ERR for all solid cancer was 0 to 0.20 Gy, and a formal dose-threshold analysis indicated no threshold; i.e., zero dose was the best estimate of the threshold. The risk of cancer mortality increased significantly for most major sites, including stomach, lung, liver, colon, breast, gallbladder, esophagus, bladder and ovary, whereas rectum, pancreas, uterus, prostate and kidney parenchyma did not have significantly increased risks. An increased risk of non-neoplastic diseases including the circulatory, respiratory and digestive systems was observed, but whether these are causal relationships requires further investigation. There was no evidence of a radiation effect for infectious or external causes of death.
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            Population Attributable Fraction of Mortality Associated with Tobacco Smoking in Japan: A Pooled Analysis of Three Large-scale Cohort Studies

            Background Quantitative measures of the burden of tobacco smoking in Asian countries are limited. We estimated the population attributable fraction (PAF) of mortality associated with smoking in Japan, using pooled data from three large-scale cohort studies. Methods In total, 296,836 participants (140,026 males and 156,810 females) aged 40-79 years underwent baseline surveys during the 1980s and early 1990s. The average follow-up period was 9.6 years. PAFs for all-cause mortality and individual tobacco-related diseases were estimated from smoking prevalence and relative risks. Results The prevalence of current and former smokers was 54.4% and 25.1% for males, and 8.1% and 2.4% for females. The PAF of all-cause mortality was 27.8% [95% confidence interval (CI): 25.2-30.4] for males and 6.7% (95% CI: 5.9-7.5) for females. The PAF of all-cause mortality calculated by summing the disease-specific PAFs was 19.1% (95% CI: 16.0-22.2) for males and 3.6% (95% CI: 3.0-4.2) for females. The estimated number of deaths attributable to smoking in Japan in 2005 was 163,000 for males and 33,000 for females based on the former set of PAFs, and 112,000 for males and 19,000 for females based on the latter set. The leading causes of smoking-attributable deaths were cancer (61% for males and 31% for females), ischemic heart diseases and stroke (23% for males and 51% for females), and chronic obstructive pulmonary diseases and pneumonia (11% for males and 13% for females). Conclusion The health burden due to smoking remains heavy among Japanese males. Considering the high prevalence of male current smokers and increasing prevalence of young female current smokers, effective tobacco controls and quantitative assessments of the health burden of smoking need to be continuously implemented in Japan.
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              Smoking decreases the duration of life lived with and without cardiovascular disease: a life course analysis of the Framingham Heart Study.

              To compare the burden of cardiovascular disease in terms of lifetime risk and life years lived with disease between smokers and non-smokers. We constructed multi-state life tables describing transitions through various cardiovascular diseases for 4723 smokers and non-smokers observed during 20 biannual observations in the Original Framingham Heart Study. Non-smokers live 8.66 (95% CI 7.61-9.63) (men) and 7.59 (95% CI 6.33-8.92) (women) years longer than smokers and more years free of cardiovascular disease: 6.22 (95% CI 5.09-7.30) years for males and 4.93 (95% CI 3.54-6.29) for females. But non-smokers spend more years with cardiovascular disease over the life course: 2.43 (95% CI 1.72-3.16) years for males and 2.66 (95% CI 1.87-3.38) years for females. The risk of cardiovascular disease before age 70 is higher among smokers, but over the entire lifecourse male non-smokers have higher risks of coronary heart disease, myocardial infarction, stroke and congestive heart failure, and female non-smokers have higher risks of coronary heart disease and congestive heart failure. Smoking, by shortening life, decreases both the probability and duration of cardiovascular disease throughout the life course. Non-smokers live many years longer and longer free of cardiovascular disease than smokers, but at the end of their life non-smokers will have lived longer with cardiovascular disease.
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                Author and article information

                Contributors
                Role: associate senior scientist
                Role: senior statistician
                Role: assistant department chief
                Role: department chief
                Role: professor
                Role: professor
                Journal
                BMJ
                BMJ
                bmj
                BMJ : British Medical Journal
                BMJ Publishing Group Ltd.
                0959-8138
                1756-1833
                2012
                2012
                25 October 2012
                : 345
                : e7093
                Affiliations
                [1 ]Department of Epidemiology, Radiation Effects Research Foundation, Hiroshima, Japan
                [2 ]Clinical Trial Service Unit, University of Oxford, Oxford OX3 7LF, UK
                Author notes
                Correspondence to: S C Darby sarah.darby@ 123456ctsu.ox.ac.uk
                Article
                sakr008399
                10.1136/bmj.e7093
                3481021
                23100333
                1f89347e-a563-4a77-a36d-87f430ad8374
                © Sakata et al 2012

                This is an open-access article distributed under the terms of the Creative Commons Attribution Non-commercial License, which permits use, distribution, and reproduction in any medium, provided the original work is properly cited, the use is non commercial and is otherwise in compliance with the license. See: http://creativecommons.org/licenses/by-nc/2.0/ and http://creativecommons.org/licenses/by-nc/2.0/legalcode.

                History
                : 17 October 2012
                Categories
                Research
                Smoking and Tobacco
                Epidemiologic Studies
                Health Education
                Health Promotion
                Smoking

                Medicine
                Medicine

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