Estimating and explaining the effect of education and income on head and neck cancer risk: INHANCE consortium pooled analysis of 31 case-control studies from 27 countries

Abstract

Low socioeconomic status has been reported to be associated with head and neck cancer risk. However, previous studies have been too small to examine the associations by cancer subsite, age, sex, global region and calendar time and to explain the association in terms of behavioral risk factors. Individual participant data of 23,964 cases with head and neck cancer and 31,954 controls from 31 studies in 27 countries pooled with random effects models. Overall, low education was associated with an increased risk of head and neck cancer (OR = 2.50; 95% CI = 2.02 - 3.09). Overall one-third of the increased risk was not explained by differences in the distribution of cigarette smoking and alcohol behaviors; and it remained elevated among never users of tobacco and nondrinkers (OR = 1.61; 95% CI = 1.13 - 2.31). More of the estimated education effect was not explained by cigarette smoking and alcohol behaviors: 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 versus high household income. 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 behavioral risk factors for these cancers and which varies across cancer sites, sexes, countries and country income inequality levels.

Keywords: epidemiology; head and neck cancer; socioeconomic inequalities.

Figure 1

The risk of head and neck cancer associated with low relative to high education and low income relative to high income adjusted for smoking and alcohol behaviors, by study and pooled. OR: odds ratios; 95%CI: 95% confidence intervals *USA Multicenter, Baltimore HOTSPOT, China (Beijing) no lowest group, second group (1v2 or 2v5). Squares: study specific OR; Size of the squares: determined by the inverse of the variance of the log OR. Horizontal lines: study specific 95% CI; Diamond: summary estimate combining the study specific estimates with random-effects models adjusted for age, sex, center, smoking [smoking status, smoking pack years (continuous), cigarettes per day] and alcohol (alcohol drinking status and alcohol frequency); Width of diamond: summary estimate 95% CI Solid vertical line-OR of 1; Dashed vertical line-summary OR, “X studies removed refers to when studies leading to heterogeneity were removed.