Socioeconomic inequalities and oral cancer risk: a systematic review and meta-analysis of case-control studies.

There is uncertainty and limited recognition of the relationship between socioeconomic inequalities and oral cancer. We aimed to quantitatively assess the association between socioeconomic status (SES) and oral cancer incidence risk. A systematic review of case-control studies obtained published and unpublished estimates of the SES risk related to oral cancer. Studies were included which reported odds ratios (ORs) and corresponding 95% CIs of oral cancer with respect to SES, or if the estimates could be calculated or obtained. Meta-analyses were performed on subgroups: SES measure, age, sex, global region, development level, time-period and lifestyle factor adjustments; while sensitivity analyses were conducted based on study methodological issues. Forty-one studies provided 15,344 cases and 33,852 controls which met our inclusion criteria. Compared with individuals who were in high SES strata, the pooled ORs for the risk of developing oral cancer were 1.85 (95%CI 1.60, 2.15; n = 37 studies) for those with low educational attainment; 1.84 (1.47, 2.31; n = 14) for those with low occupational social class; and 2.41 (1.59, 3.65; n = 5) for those with low income. Subgroup analyses showed that low SES was significantly associated with increased oral cancer risk in high and lower income-countries, across the world, and remained when adjusting for potential behavioural confounders. Inequalities persist but are perhaps reducing over recent decades. Oral cancer risk associated with low SES is significant and comparable to lifestyle risk factors. Our results provide evidence to steer health policy which focus on lifestyles factors toward an integrated approach incorporating measures designed to tackle the root causes of disadvantage.