Social gradient in cancer incidence in Costa Rica: Findings from a national population-based cancer registry

Abstract

Background: The main evidence regarding social inequalities in cancer risk comes from industrialized countries. The aim of this manuscript was to analyze the association between cancer incidence and socioeconomic position (SEP) in a middle-income country (Costa Rica) between 2011 and 2015. Methods: An ecological study at the level of the electoral district was conducted. The 477 districts were divided by area and wealth using the 2011 Census. The sample was defined using the National Electoral Rolls used for presidential elections of 2006 and 2010 (N = 2 798 517). 44 799 cancer cases were included coming from the Costa Rican Cancer Registry. Cox models were used. Results: All cancer sites combined, we observed a positive gradient, with incidence being lower in the poorest districts than in the wealthiest (HRQ2 = 0.98 [0.93−1.03], HRQ3 = 0.92 [0.85−0.99], HRQ4 = 0.83 [0.77−0.88]). For colon, skin, breast, prostate, thyroid and other cancer sites, a positive social gradient was observed. For stomach, lung, and cervical (invasive or in-situ) cancers, a negative social gradient was found. For uterine cancer and lymphoma (no-Hodgkin), there was no significant relationship between wealth and incidence. For skin cancer, incidence was higher in rural as compared to urban areas after adjustment for wealth. For lung, cervical and uterine cancer, incidence was lower in rural as compared to urban area after adjustment for wealth. Conclusions: The all-cancer combined results were in contradiction with the international literature but confirmed recent study results in Costa Rica. It confirmed the importance of studying socioeconomic inequalities in middle-income countries.