*Bull World Health Organ. 2013 May 1;91(5):332-40. doi: 10.2471/BLT.12.108092.

Trends in smoking and lung cancer mortality in Japan, by birth cohort, 1949-2010.

Funatogawa I, Funatogawa T, Yano E.

Department of Public Health, Teikyo University Graduate School of Public Health, 2-11-1 Kaga, Itabashi-ku, Tokyo 173-8605, Japan. ifunatogawa-tky@umin.ac.jp

 

ABSTRACT

OBJECTIVE: To determine smoking trends in Japan in comparison with lung cancer mortality.

METHODS: Age-specific smoking prevalence among cohorts born between 1897 and 1985 were determined for the period 1949-2010. The percentages of the cohorts born between 1893 and 1979 who initiated smoking early (e.g. before the age of 20 years) were determined. The results were compared against lung cancer mortality rates in people aged 40-84 years belonging to cohorts born between 1868 and 1968.

FINDINGS: In males, smoking prevalence was generally high, particularly among those born before the late 1950s, and early initiation was fairly uncommon. Early initiation was most common among recent birth cohorts of males, who showed relatively low prevalences of smoking. In females, the prevalence of smoking was generally low and early initiation was very uncommon, particularly among those born in the late 1930s and before the late 1940s, respectively. Recent cohorts of females showed relatively high prevalences of smoking and relatively high percentages of early initiation. In both sexes, lung cancer mortality was generally low but increased over the study period.

CONCLUSION: Lung cancer mortality in Japanese males was relatively low given the high prevalence of smoking, perhaps because early initiation was fairly uncommon. Over the last four decades, however, early initiation of smoking has become more common in both sexes. The adverse effect this is likely to have on lung cancer mortality rates has probably not been observed because of the long time lag between smoking initiation and death from lung cancer.

PMID: 23678196

 

Supplement

Despite the harmful health effects, almost 1.25 billion people smoke worldwide. Although early smoking initiation may greatly increase mortality, the subsequent deaths from smoking typically become evident in elderly individuals. Indeed, the interval between smoking initiation and death is very long. This obscures the impact of early smoking in most nations, especially developing countries, where tobacco consumption is increasing, but data about smoking and mortality are scarce. The experiences of countries that have long-term smoking data should help to clarify the situation for the rest of the world.

Figure1

Based on data from repeated cross-sectional surveys, Funatogawa et al.1 assessed smoking initiation and prevalence in Japan in relation to lung cancer mortality by birth cohort (i.e., people born within a defined period). Funatogawa et al.2 also assessed smoking initiation in Great Britain. Several age-specific smoking indicators (initiation, prevalence, lung cancer mortality) were plotted with birth year in the figures.1, 2 Lung cancer mortality is now used as a measure of a population’s past exposure to smoking. This kind of study is surprisingly rare because of the scarcity of historical smoking-initiation data. This supplement further explains the findings and significance of the study by comparing the results in Japan with those in Great Britain and the United States. Figure 1 shows smoking indicators in the United States.3, 4 Cigarette smoking is shown in the United States.4

Table 1

Table 1 shows data in selected birth cohorts. Japanese men showed high smoking prevalence but lower rates of early smoking initiation (<3%, <7%, and >70% at 15, 17, and 29 years, respectively, in the 1900–1925 birth cohorts) and correspondingly lower lung cancer mortality (in excess of 1 per 1000 at 60–64 years or older). American men showed high rates of early smoking initiation (>20%, >35%, and >70% at 15, 17, and 29 years, respectively, in the 1900–mid-1940s birth cohorts) and correspondingly high lung cancer mortality (in excess of 1 per 1000 at 50–54 and 55–59 years). British men showed higher early smoking initiation (>32%, >50%, and >80% at 15, 17, and 29 years, respectively, in the 1900–1925 birth cohorts) and correspondingly higher lung cancer mortality (in excess of 1 per 1000 at 50–54 years).

Smoking habits and lung cancer mortality can change markedly during only two or three decades in birth year. In American women, smoking initiation increased between the late-1890s and early-1920s birth cohorts (1% to 4%, 2% to 12%, and 10% to 46% at 15, 17, and 29 years, respectively). Correspondingly, the age at which the lung cancer mortality exceeded 1 per 1000 became younger (from 80–84 to 60–64 years). In British women, smoking initiation increased between the late-1890s and mid-1920s birth cohorts (2% to 12%, 4% to 24%, and 13% to 54% at 15, 17, and 29 years old, respectively). Correspondingly, the age at which lung cancer mortality exceeded 1 per 1000 became younger (75–79 to 60–64 years). The age also rapidly became younger among men since the 1870s or 1880s birth cohorts in the three countries, but smoking initiation in these cohorts is unknown.

The short-term decreases and increases with birth year (i.e., within two decades) were seen in Japanese men (around the late 1930s cohorts), American women (between the 1940s and mid-1950s cohorts), and British men and women (around the mid-1930s cohorts). Correspondingly, lung cancer mortality in middle-aged or elderly individuals also changed. Japanese women showed a long-term trend with a decrease and increase in smoking prevalence with birth year (i.e., six or seven decades). Furthermore, in Japanese men, American women, and British women, smoking prevalence decreased, but early smoking initiation increased with birth year in more recent cohorts. Their combined effects on mortality have yet to be seen. These complex changes in smoking habits render interpretation of the relationship between smoking and mortality difficult.

Smoking initiation at certain early ages is particularly important because it suggests the duration of smoking, and smoking at early ages may greatly increase mortality. Smoking prevalence during adulthood, which may include the effects of cessation, is also important. Smoking habits change non-monotonically with age and birth year. Trends in smoking habits at different ages are not necessarily the same. Early smoking initiation is increasing in several countries. Risks in the distant future, more than 50 years later, should not be underestimated. Indeed, long-term monitoring, focusing on birth cohorts, is vitally important.

Funding: Grant in Aid for Scientific Research (24500349 to IF) from the Japan Society for the Promotion of Science

 

References

  1. Funatogawa I, Funatogawa T, Yano E. Trends in smoking and lung cancer mortality in Japan, by birth cohort, 1949–2010. Bull World Health Organ 2013;91:332-40.
  2. Funatogawa I, Funatogawa T, Yano E. Impacts of early smoking initiation: long-term trends of lung cancer mortality and smoking initiation from repeated cross-sectional surveys in Great Britain. BMJ Open 2012;2:e001676.
  3. Funatogawa I. The first generation in which many women began smoking. Lancet 2013 381(9876):1455. (Letter)
  4. Burns DM, Lee L, Shen LZ, et al. Cigarette smoking behavior in the United States. In: Burns DM, Garlfinkel L, Samet J, eds. Smoking and tobacco control monograph no. 8. Bethesda, MD.: National Cancer Institute, 1997:13-112.
  5. The detailed data files of the WHO Mortality Database. Geneva: World Health Organization, 2012. (Accessed Feb 8, 2014, at http://www.who.int/healthinfo/statistics/mortality_rawdata/en/index.html)

 

* The Bulletin is one of the top 10 public and environmental health journals with an impact factor of 5.250, according to the Institute of Scientific Information (ISI).

Multiselect Ultimate Query Plugin by InoPlugs Web Design Vienna | Webdesign Wien and Juwelier SchönmannMultiselect Ultimate Query Plugin by InoPlugs Web Design Vienna | Webdesign Wien and Juwelier Schönmann