Occupational disparities in survival from common cancers in Japan: Analysis of Kanagawa cancer registry

Masayoshi Zaitsu; Yasuki Kobayashi; Enkhtuguldur Myagmar-Ochir; Takumi Takeuchi; Gen Kobashi; Ichiro Kawachi

doi:10.1016/j.canep.2022.102115

Occupational disparities in survival from common cancers in Japan: Analysis of Kanagawa cancer registry

Cancer Epidemiol. 2022 Apr:77:102115. doi: 10.1016/j.canep.2022.102115. Epub 2022 Jan 29.

Authors

Masayoshi Zaitsu¹, Yasuki Kobayashi², Enkhtuguldur Myagmar-Ochir³, Takumi Takeuchi⁴, Gen Kobashi³, Ichiro Kawachi⁵

Affiliations

¹ Department of Public Health, Dokkyo Medical University School of Medicine, Shimotsuga-gun, Tochigi, Japan; Department of Public Health, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan; Department of Urology, Kanto Rosai Hospital, Kawasaki, Kanagawa, Japan. Electronic address: m-zaitsu@dokkyomed.ac.jp.
² Department of Public Health, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan.
³ Department of Public Health, Dokkyo Medical University School of Medicine, Shimotsuga-gun, Tochigi, Japan.
⁴ Department of Urology, Kanto Rosai Hospital, Kawasaki, Kanagawa, Japan.
⁵ Department of Social and Behavioral Sciences, Harvard T.H. Chan School of Public Health, Boston, MA, USA.

PMID: 35104770
DOI: 10.1016/j.canep.2022.102115

Abstract

Background: Little is known about occupational disparities in survival for common cancer sites in Japan.

Methods: Using data from a population-based cancer registry, we identified 32,870 cancer patients diagnosed during 1992-2011. We followed the patients for 5 years (median follow-up time 5.0 years). For each individual, we classified their longest-held occupation into 5 classes (upper non-manual, lower non-manual, manual, farmer, and others) following the Erikson-Goldthorpe-Portocarero scheme. Poisson regression models were used to estimate overall and site-specific mortality rate ratios (MRRs) and 95% confidence intervals (CI) for each occupational class, adjusted for sex, age, and diagnosis year. Upper non-manual workers served as the reference group. Additionally, using a binary categorization of occupations (manual workers versus non-manual workers), a causal mediation analysis with 4-way decomposition was performed to investigate the potential mediation of the association between occupation and overall mortality by cancer stage.

Results: Overall prognosis was good in this population (5-year overall survival was 81.7%). Compared with upper non-manual workers, both overall and cancer-specific mortality was higher in lower non-manual workers (MRR=1.14, 95% CI 1.05-1.24) and manual workers (MRR=1.40, 95% CI 1.29-1.53). After adjusting for the mediating influence of prognostic factors (stage and treatment), the observed occupational differences were attenuated but remained significant in manual workers: MRR = 1.23 (95% CI 1.08-1.39). Observed occupational disparities tended to be attributable to common cancers, i.e., stomach and lung among men and female breast cancer. Additionally, manual workers had 1.25 times higher odds for advanced stage. In the mediation analysis, the overall proportion explained by mediating effect of cancer stage was 29% (4% due to mediated interaction and 25% due to pure indirect effect).

Conclusion: We documented occupational disparities in survival from commonly-occurring cancers in Japan. Occupational differences in cancer stage may explain one-third of the survival disparities.

Keywords: Cancer; Japan; Occupational class; Socioeconomic status; Survival.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Female
Humans
Japan / epidemiology
Male
Neoplasms* / epidemiology
Occupations*
Prognosis
Registries