Socioeconomic status in relation to risks of major gastrointestinal cancers in Chinese adults: a prospective study of 0.5 million people

Background: Low socioeconomic status (SES) is associated with higher risk of certain gastrointestinal (e.g. colorectal, pancreatic, and liver) cancers in Western populations. Evidence is very limited in China where correlates and determinants of SES differ from those in the West. Methods: The prospective China Kadoorie Biobank recruited 512,715 adults (59% women, mean age 51 years) from 10 (5 urban, 5 rural) regions. During 10 years of follow-up, 27,940 incident cancers (including 3061 colorectal, 805 pancreatic, and 2904 liver) were recorded among 510,131 participants without prior cancer at baseline. Cox regression was used to estimate adjusted hazard ratios (HRs) for specific cancers associated with area-level (e.g. per capita gross domestic product, disposable income) and individual-level (e.g. education, household income) SES. Results: Area-level SES and household income showed positive associations with incident colorectal and pancreatic cancer and inverse associations with liver cancer (p for trend <0.05). Education showed no association with colorectal cancer but inverse associations with pancreatic and liver cancer, with adjusted HRs comparing university to no formal schooling being 1.05 (95% CI 0.85-1.29), 0.49 (0.28-0.85), and 0.61 (0.47-0.81), respectively. Potential risk factors (e.g. smoking, alcohol) explained partly the inverse associations of education with pancreatic and liver cancer (17.6% and 60.4%, respectively), respectively. Conclusions: Among Chinese adults, the associations of SES with gastrointestinal cancers differed by cancer type and SES indicator. Potential risk factors partially explained the inverse associations of education with pancreatic and liver cancer. Impact: The different associations between SES with gastrointestinal cancers may inform cancer prevention strategies.