Method: 23,964 cases with head and neck cancer and 31,954 controls from 27 countries in the INternational Head And Neck Cancer Epidemiology (INHANCE) consortium. Random effects models used to compute adjusted odds ratios (OR) and 95% confidence intervals (CI) associated with low vs. high educational attainment and low vs. high household income.
Result: Overall, low education was associated with an increased risk of head and neck cancer (OR = 2.50; 95%CI 2.02 to 3.09). This risk association was stronger in men, for hypopharyngeal and laryngeal cancers, and in North America. Overall one-third of the increased risk was not explained by differences in the distribution of cigarette smoking and alcohol behaviours; one-quarter was not explained when other tobacco use and diets low in fruit and vegetables were considered; and it remained elevated among never users of tobacco and non-drinkers (OR = 1.61; 95%CI 1.13 to 2.31). More of the estimated education effect was not explained by cigarette smoking and alcohol behaviours: in women than in men, in older than younger groups, in the oropharynx than in other sites, in South/Central America than in Europe/North America, and was strongest in countries with greater income inequality. Similar findings were observed for the estimated effect of low vs high household income.
Conclusion: The lowest levels of income and educational attainment were associated with more than 2-fold increased risk of head and neck cancer, which is not entirely explained by differences in the distributions of behavioural risk factors for these cancers, and which varies across cancer sites, sexes, countries, and country income inequality levels. This knowledge should underpin prevention strategies.