Abstract
Little is known about socioeconomic inequalities in male cancer incidence in nonwestern settings. Using the nationwide clinical and occupational inpatient data (1984‐2016) in Japan, we performed a multicentered, matched case–control study with 214 123 male cancer cases and 1 026 247 inpatient controls. Based on the standardized national classifications, we grouped patients’ longest‐held occupational class (blue‐collar, service, professional, manager), cross‐classified by industrial cluster (blue‐collar, service, white‐collar). Using blue‐collar workers in blue‐collar industries as the referent group, odds ratios (ORs) and 95% confidence intervals (CIs) were estimated by conditional logistic regression with multiple imputation, matched for age, admission date, and admitting hospital. Smoking and alcohol consumption were additionally adjusted. Across all industries, a reduced risk with higher occupational class (professionals and managers) was observed for stomach and lung cancer. Even after controlling for smoking and alcohol consumption, the reduced odds persisted: OR of managers in white‐collar industries was 0.80 (95% CI 0.72‐0.90) for stomach cancer, and OR of managers in white‐collar industries was 0.66 (95% CI 0.55‐0.79) for lung cancer. In white‐collar industries, higher occupational class men tended to have lower a reduced risk for most common types of cancer, with the exception of professionals who showed an excess risk for prostate cancer. We documented socioeconomic inequalities in male cancer incidence in Japan, which could not be explained by smoking and alcohol consumption.
Highlights
Cancer is a leading cause of death in developed countries, and in 2016, the total incidence of cancer was estimated to be 867 408 in Japan.[1]
Overall cancer mortality has been declining in Japan, where stomach cancer appeared to play a large role for the decrease due to improved risk factors and treatment strategies, overall cancer incidence has been continuously increasing.[2]
Smoking is less prevalent in higher occupational class, and this may account for a lower risk of stomach and lung cancer.[4,5]
Summary
Cancer is a leading cause of death in developed countries, and in 2016, the total incidence of cancer was estimated to be 867 408 (male 501 527 and female 365 881) in Japan.[1]. Compared with Western countries, the distribution of H. pylori infection (stomach cancer risk) is higher in Japan.[2,10] For socioeconomic patterns for other potential cancer risks related to occupation, work‐related psychological stress partly differ between these two contexts.[11] In contrast to Western countries, where occupational stress is typically higher among low‐occupational classes compared with high‐occupational ones, the opposite pattern has been seen in Japan (eg high suicide rate in managerial position).[6,11] Recently, with regard to major cancer incidence among women in Japan, we found a reduced risk of stomach and lung cancer and an excess risk of breast cancer in higher occupational class using individual‐level data.[10] the association among men remains unclear in Japan. We determined whether the observed association persists even after controlling for smoking and alcohol consumption
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