Educational inequalities in all and site-specific cancer mortality: Mediation analysis of health behaviors from a 7-year cohort study in Japan

BackgroundPrevious studies have reported educational inequalities in all and site-specific cancer mortality. However, the mechanisms underlying this association remain unclear. We investigated the association between educational level and all- and site-specific cancer mortality and examined potential mediating factors.MethodsWe conducted a longitudinal study using data from the Japan Gerontological Evaluation Study (JAGES), initiated in 2010 with 7-year follow-up targeting independent adults aged ≥65 years. Self-report questionnaire data were linked to mortality records from municipal registries. Educational level was exposure (<10/10-12/>12 years for competing risk models and <10/≥10 years for causal mediation analysis). All- and site-specific cancer mortality were outcomes. Competing risk models estimated sub-distribution hazard ratios (SHRs) and 95% confidence intervals (CIs). Causal mediation analysis assessed mediating effects of smoking status, drinking status, health examination, vegetable and/or fruit intake, and walking time.ResultsAmong 43,478 participants (46.6% men, mean age 73.7 years), the 7-year mortality from all cancers was 5.1%. Low educational level was associated with higher all-cancer mortality (SHR for the lowest compared with the highest 1.27; 95%CI, 1.13-1.44). Similar associations were observed for tracheal and lung, and esophageal cancer mortality. The association between educational level and all cancer mortality was significantly mediated by smoking status (5.6%), health examination (8.0%), and walking time (7.1%), but not by drinking status and vegetable and/or fruit intake.ConclusionLower educational level was associated with a higher risk of all cancer, tracheal and lung cancer, and esophageal cancer mortality. Health behaviors partially explained these associations.